Stability and Viability of Probiotics in Fermented Dairy Products During Storage: A Systematic Literature Review

Abstract

This study aimed to evaluate the survival rate (stability) and the living cell counts (viability) of probiotics in fermented dairy products (cheese and yogurt) under various storage conditions through a systematic literature review. The Population, Intervention, Comparison, and Outcome (PICO) framework was used to determine the research question. The literature selection process followed the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) 2020 guidelines. Articles published during 2013–2022 in the Scopus and PubMed databases were used. Keyword searches yielded a total of 864 studies, among which 32 articles were chosen for this review. The stability and viability of probiotics in fermented dairy products stored for up to 14 or 15 days (first shelf-life period) and 28 or 30 days (second shelf-life period) were determined. The stability of probiotics in fermented dairy products during storage was influenced by the (i) probiotic genus, (ii) microencapsulation materials, (iii) storage temperature, and (iv) packaging type. The factors that affected the viability of probiotics in fermented dairy products during storage were (i) product form and (ii) storage temperature. The stability of most probiotics decreased under the various storage conditions and until the 30^th day. However, most products met the minimum standard (10⁶ CFU/g) for probiotic viability to be considered functional foods with health benefits.

1. Introduction

Probiotics are microorganisms that when consumed in sufficient amounts, alter the colon microflora and provide health benefits to the host [1, 2]. Probiotics include various bacterial and fungal species present in foods. From 3000 to 2000 BC, civilizations such as Egypt, Greece, Rome, and India left many records indicating that cheese and yogurt were commonly consumed. Geographic separation and cultural differences resulted in diverse fermented dairy products, depending on the raw materials, environmental conditions, and sensory preferences in each region [3]. A food product can be considered functional if proven to have a beneficial effect on one or more target functions relevant to improving health status and/or reducing the risk of a disease beyond the nutritional benefits [4, 5]. Fermented dairy products are important commercial probiotic products because they are easy to produce, affordable, and milk as a raw material has physicochemical and nutritional properties that ensure the survival of probiotics during fermentation and storage [2]. Milk has a complex biochemical composition and high water activity, making it an optimal growth medium for probiotics. In 100 g of milk, there are 83–87 g of water, 3.5 g of protein, and 4.7–5.1 g of lactose [6].

Probiotic cultures in fermented foods should remain stable (survival rate) and viable (living cell counts) from the fermentation process to storage and through digestion to provide health benefits to the host [7]. According to the CODEX Standard 243-2003, probiotic foods should contain a minimum of 10⁶–10⁷ CFU/g living cells through the storage period to ensure the probiotic content results in health benefits [8, 9]. This number ensures that enough probiotics survive the passage through the gastrointestinal tract which contains gastric acid (pH 1–2) and bile salts (pH 5–6.5) to reach the colon [10]. Therefore, the storage conditions of fermented dairy products should be appropriate to ensure that probiotics remain stable and viable until their consumption. These conditions include the oxygen content, temperature, pH, and storage period [11].

No recent systematic reviews have been published on probiotic stability and viability in fermented dairy products (cheese and yogurt) under various storage conditions. Nevertheless, there have been review articles focused on the viability of probiotic microorganisms in cheese during production and storage [10], the survival of probiotics during processing and storage [11], cell viability and functionality of probiotic bacteria in dairy products [12], and the structural stability and viability of microencapsulated probiotic bacteria [13]. On the other hand, in recent years, many research articles have been published on this topic. Therefore, the abundant literature necessitates a systematic review, so the facts can be presented in a comprehensive and balanced manner to facilitate future studies.

2. Methodology

A systematic literature review (SLR) employs systematic and unambiguous procedures to minimize bias during the search, identification, assessment, synthesis, analysis, and summarization of studies. Thus, an SLR can provide reliable findings and conclusions that assist decision-makers in further research [14]. The present study is an SLR. The literature sources were research articles on the stability and viability of probiotics in fermented dairy products (cheese and yogurt) during storage. Probiotic viability is defined as the number of probiotics being alive and able to form a colony, and expressed as colony forming unit (CFU) per gram or milliliter. While probiotic stability is defined as the ability of a probiotic to resist environmental stressors and maintain its initial population over a defined time period. In other words, probiotic stability represents survival rate of probiotic. Survival rate (SR) is calculated based on the cell count of probiotic in each phase and expressed as percentage (%) using the equation: SR (%) = [log CFU N/log CFU N0] × 100, where N0 and N are the population values before and after the assay, respectively [15].

The literature search was conducted using the Scopus and PubMed databases after determining the research question (RQ), employing the Population, Intervention, Comparison, and Outcome (PICO) framework. The literature selection process followed the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) 2020 guidelines, meeting inclusion and exclusion criteria. Data synthesis was conducted based on the information needs, aligned with the research objectives and the PICO framework. Data were analyzed to obtain a summary of results, presented in tables. Finally, the data that addressed the RQ were organized and reported in the form of an SLR.

Table 1 shows the PICO framework used in this review. The RQs were formulated based on this framework to ensure they were relevant to the scope of the study. The following RQs were explored: (1) How does the stability and viability of probiotics in fermented dairy products (cheese and yogurt) vary under various storage conditions; (2) What factors can affect the stability and viability of probiotics in fermented dairy products (cheese and yogurt) during storage.

Table 1: PICO framework

Population	Fermented milk product (cheese and yoghurt)
Intervention	Various conditions during storage
Comparison	Probiotics stability and viability
Outcome	There are various conditions affecting probiotics stability in fermented dairy products (cheese and yoghurt) during storage

The literature search involved the use of keywords assisted by Boolean operators to increase the efficiency, precision, and comprehensiveness of the process. Relevant keywords for the database search were organized based on the research objectives to obtain pertinent studies. Table 2 shows the keyword combinations used for this review.

Table 2: Keyword combinations

Database	Keyword	Search Field	Literatures Found	Search Date
PubMed	Search: ((probiotic OR “encapsulated probiotic” OR “microencapsulated probiotic”) AND (stability OR viability OR “growth rate” OR “survival rate”)) AND ((storage OR “during storage” OR shelf-life OR “shelf life” OR “cold storage” OR refrigerated OR “room temperature” OR packing OR packaging) AND (cheese OR yoghurt OR yogurt))	All Fields	212	26th February 2023
Scopus	(TITLE-ABS-KEY((probiotic OR “encapsulated probiotic” OR “microencapsulated probiotic”) AND (stability OR viability OR “growth rate” OR “survival rate”))) AND (TITLE-ABS-KEY((storage OR “during storage” OR shelf-life OR “shelf life” OR “cold storage” OR refrigerated OR “room temperature” OR packing OR packaging) AND (cheese OR yoghurt OR yogurt)))	Article title, Abstract, Keywords	652	26th February 2023

The inclusion criteria determined the validity and reliability of the selected studies, ensuring the absence of bias [16]. The inclusion criteria were as follows: literature available in the PubMed and Scopus databases, with a related topic based on the PICO framework and RQ, research or experimental articles, published in 2013–2022, in English, indexed in a journal with a minimum ranking of Scopus Q3, and with the full text accessible. Two researchers (MZZ and RBE) independently screened articles based on established eligibility criteria. Any discrepancies arise during this stage were resolved through discussion with other two researchers (DP and AN). Finally, the researchers involved in the selection process (MZZ, RBE, DP and AN) conducted article review to determine article eligibility based on the study objective and criteria.

Figure 1: PRISMA 2020 Flowchart of the study selection process

The literature sources were assessed following the PRISMA 2020 guidelines [17]. Literature meeting the inclusion criteria and passing the PRISMA 2020 selection were chosen for further evaluation and data analysis [14]. The literature selection process comprised three stages (Fig. 1): identification, screening, and inclusion. First, the studies were identified in the databases using keywords (864), some were then excluded using automation tools and duplication record (454 excluded), the eligibility of the remaining documents (410) was determined based on the PICO framework (347 ineligible) resulting in 63 documents. The inclusion criteria were subsequently applied and finally resulting in 32 articles for the review. The data synthesis stage includes the extraction and classification of relevant data from each selected study [18]. The data analysis stage involves evaluating the synthesized data, combining and summarizing information from the selected articles. At this stage, the formulated RQ can be answered based on the obtained data [14, 18].

Risk of bias assessment for all selected studies were performed using Joanna Briggs Institute (JBI) Critical Appraisal Tool for Quasi-Experimental Studies [19]. This tool consists of nine questions that are used to asses bias by scoring yes=1, no=-1, unclear=0, and not applicable=0. Total scores obtained were then converted to percentages with the maximum scores (9 points) and categorized according to the level of risk of bias. Studies with a score range of 20–49%, 50–79% and 80–100% were categorized as having high, moderate and low risk of bias, respectively. The nine questions covered bias related to these domains: (1) temporal precedence; (2) selection and allocation; (3) confounding factors; (4) administration of intervention/exposure; (5) measurement periodicity; (6) measurement equality; (7) reliability of outcome; (8) sample retention; and (9) statistical analysis. One researcher (MZZ) conducted the initial evaluation which was subsequently validated by other two researchers (DP and AN). The summary of the risk of bias assessment was visualized as Traffic Light Plot and Summary Bar Chart which were generated using the Robvis tool [20].

3. Results and discussion

Based on the 32 articles screened using PRISMA 2020, various conditions influenced the stability and viability of probiotics in fermented dairy products (cheese and yogurt) during storage. These conditions were categorized into product factors (product form, pH, and raw material), probiotic factors (genus and microencapsulation material), and product storage factors (storage temperature and packaging type). The storage duration of the fermented milk products was determined based on the data from the selected articles, and was divided into two periods: storage for up to 14 or 15 days (first period) and 28 or 30 days (second period). Data synthesis was conducted for each factor from the selected articles to obtain accurate results regarding the factors affecting the stability and viability of probiotics. Table 3 summarizes the key information extracted from the 32 articles by product type [21–52].

Table 3: Key information list of included articles for review

Ref.	Authors (year)	Fermented Dairy Product	Assessed Probiotic	Storage
				Temperature (°C)	Time (Days)
[21]	Cichosz et al. (2014)	Dutch-type cheese	Lactobacillus sp.	4	90
		Swiss-type cheese	Lactobacillus sp.	4	90
[22]	Martins et al. (2018)	Boursin cheese	Bifidobacterium sp. Lactobacillus sp.	4	35
[23]	Moraes et al. (2018)	Coalho cheese	Lactobacillus sp. Streptococcus sp.	4	28
[24]	Mushtaq et al. (2016)	Himalayan cheese (kalari)	Lactobacillus sp.	4	30
[25]	Łepecka et al. (2021)	Organic cheese	Lactobacillus sp.	4–10	60
[26]	Chaves and Gigante (2016)	Prato cheese	Bifidobacterium sp. Lactobacillus sp. Lactococcus sp.	12	60
[27]	Ehsani et al. (2018)	White cheese	Lactobacillus sp.	4	60
[28]	Nejati et al. (2016)	UF-feta cheese	Lactobacillus sp.	4	60
[29]	Moghari et al. (2014)		Bifidobacterium sp. Lactobacillus sp.	8	60
[30]	Anihouvi and Kesenkaş (2022)	Wagashi cheese	Enterococcus sp. Lactobacillus sp.	4	30
[31]	Tologana et al. (2022)	Cream cheese	Lactobacillus sp.	4	35
[32]	Ningtyas et al. (2019)		Lactobacillus sp.	4	35
[33]	Speranza et al. (2018)		Bifidobacterium sp. Lactobacillus sp.	4	28
[34]	Hain et al. (2021)	Yoghurt	Bifidobacterium sp.	-18	28
[35]	Afzaal et al. (2022)		Bifidobacterium sp.	4	28
[36]	Abdelazez et al. (2017)		Bifidobacterium sp.	-18	60
[37]	Menezes et al. (2022)		Lactobacillus sp.	4	35
[38]	Chen et al. (2017)		Bifidobacterium sp.	4 & 25	21
[39]	Shu et al. (2017)		Lactobacillus sp.	4 & 25	21
[40]	Chen et al. (2018)		Lactobacillus sp.	28 & 37	30
[41]	Yasmin et al. (2018)		Bifidobacterium sp.	4–10	28
[42]	Dantas et al. (2021)		Bifidobacterium sp. Lactobacillus sp. Streptococcus sp.	5	30
[43]	Nguyen et al. (2013)		Bifidobacterium sp. Lactobacillus sp.	4	28
[44]	Mahmoudi et al. (2021)		Bifidobacterium sp. Lactobacillus sp. Streptococcus sp.	4	28
[45]	Zhang et al. (2022)		Bifidobacterium sp. Lactobacillus sp. Streptococcus sp.	4	28
[46]	Ospanov et al. (2022)		Combination (Bifidobacterium sp.,Lactobacillus sp., Streptococcus sp.)	4	28
[47]	Ribeiro et al. (2014)	Stirred yoghurt	Lactobacillus sp.	5	35
[48]	Bosnea et al. (2016)		Lactobacillus sp.	4	45
[49]	Jouki et al. (2021)	Yoghurt powder	Lactobacillus sp.	25	84
[50]	Kadri et al. (2018)	Set yoghurt	Bifidobacterium sp. Lactobacillus sp. Streptococcus sp.	4	28
[51]	Frakolaki et al. (2021)		Bifidobacterium sp.	4	30
[52]	Pinto et al. (2019)	Greek yoghurt	Bifidobacterium sp. Lactobacillus sp. Streptococcus sp.	4	30

Figure 2: Summary bar chart of risk of bias assessmen

Figure 3: Traffic light plot of risk of bias assessment

The risk of bias assessment revealed a notable variation in quality of 32 selected studies. As presented at risk of bias summary (Fig. 2), 28 (87.5%) out of 32 studies are classified as having low risk of bias, while the rest 4 (12.5%) studies categorized as having a moderate risk of bias. Most biases resulted from D5 (bias arising from measurement periodicity) involving 7 studies, D2 (bias arising from selection and allocation) involving 3 studies and D3 (bias arising from confounding factors) involving 3 studies (Fig. 3). Two studies having a bias arising from D7 (reliability of outcome) which did not have clear information on differentiating probiotic strains during the assessment of viability. Despite these gaps, all studies provided a clear temporal relationship between the intervention and the outcome (D1), administration exposure (D4), measurement equality (D6) and sample retention (D8), ensuring the technical validity of the synthesized data.

3.1 Product form

Viability data for 14 or 15 days of storage showed that all products met the minimum probiotic content standard (10⁶ CFU/g) (Table 4). Sixteen out of 17 products stored for 28 or 30 days also met the standard. The fermented dairy products in Table 4 are considered probiotic products, except for powdered yogurt stored for 28 or 30 days, which did not meet the standard. The low viability of powdered yogurt was attributed to its small particle size, which makes it more sensitive to the storage environment because of its larger surface area, compared to solid, liquid, and semi-solid forms [53]. One of the factors that influence probiotic viability is water activity (aw) where aw in solid form product is lower than aw in semi liquid or liquid form product [54]. Probiotic remain metabolically active (high viability) in high aw environment, but it tends to enter the dormancy state in low aw environment. In addition, powdered yogurt stored at 25 °C exhibited a rapid decrease in viability because of the diffusion of moisture and oxygen into the cells, promoting the metabolic activity of the probiotic microorganisms and resulting in oxidative damage because most probiotics are anaerobic [53, 55, 56].

Furthermore, the number of probiotics may increase or decrease during the storage period. The method proposed by dos Santos et al. [15] can be used to determine the stability (or survival rate) by calculating the percentage of probiotics remaining after the test, divided by the population before the test. As shown in Table 4, the number of most probiotics in fermented dairy products changed, with decreased probiotic cell counts observed during storage for all products. For 14 or 15 days of storage, seven out of 13 products showed a decrease in probiotic counts. Likewise, for 28 or 30 days of storage, 14 out of 17 products experienced a decrease. The drop in probiotic counts in fermented milk products during storage is due to loss of proteolytic activity (protease enzymes produced by probiotics), the decrease in the concentration of substrate (lactose), exposure to oxygen from the storage environment, and the accumulation of probiotic metabolic products (organic acids and peroxides) due to post-acidification activities. These factors cause the growth rate of probiotics to decline toward the death phase [43, 57, 58, 59, 60, 61, 62]. On the other hand, probiotic viability met the standard for liquid, solid, and semi-solid products, except for powdered products stored for 28 or 30 days. Thus, in term of standard number or probiotic that should be present in probiotic product, the product form affects probiotic stability, but does not impact probiotic viability in fermented dairy product of selected studies.

Table 4: Effect of product form and pH on probiotics stability and viability in fermented dairy products during storage

Fermented Milk Product			Viability (log10 CFU/g)			Stability (%)		Reference
Form	Typea, b, c	pH	Before Storage	14/15th Day	28/30th Day	14/15th Day	28/30th Day
Powder	Yoghurt powder (25oC)	4.2	8.67	6.43	4.89	-	-	[49]
Liquid	Yoghurt	4.5	7.69	-	7.11	-	-	[43]
	Yoghurt	4.6	8.33	8.39	8.45	100	100	[42]
	Stirred yoghurt	4.8	7.42	7.04	6.93	-	-	[48]
Solid	Dutch-type cheese	5.6	9.00	-	8.90	-	-	[21]
	Coalho cheese (goat milk)	5.2	8.28	8.59	8.72	-	-	[23]
	Organic cheese	5.0–5.1	8.56	-	8.54	-	-	[25]
	Himalayan cheese (buffalo milk)	5.4–5.5	9.24	8.16	7.24	-	-	[24]
	Prato cheese	5.0–5.1	8.63	8.38	8.25	-	-	[26]
	Swiss-type cheese	5.5	8.23	-	8.20	-	-	[21]
	Wagashi cheese	4.9–5.6	8.79	8.97	8.46	-	-	[31]
Semi-solid	Boursin cheese (goat milk)	44	8.50	8.30	8.30	-	-	[22]
	White cheese	6.1–6.2	9.81	7.74	6.72	-	-	[27]
	UF-feta cheese	4.8	8.09	8.13	6.36	-	-	[30]
	Cream cheese	4.7	8.90	9.23	8.56	-	-	[32]
	Set yoghurt	5.3	9.05	7.00	6.30	-	-	[50]
	Greek yoghurt	4.7	8.80	8.87	9.03	-	-	[52]

^a) Lactobacillus sp. probiotics, ^b) Cow milk (unless stated otherwise), ^c) Storage temperature at 4–5 °C (unless stated otherwise)

3.2 Product pH

The pH values of fresh fermented dairy products (immediately after fermentation) ranged from 4.2 to 6.2 (Table 4). This pH range falls into the acidic product category, suitable for the growth of probiotic species, such as Bifidobacterium spp., Enterococcus spp., Lactobacillus spp., Lactococcus spp., and Streptococcus spp. Bifidobacterium spp. grow in a pH range of 4.5–8.5, with optimal growth at a neutral pH (6.5–7.0) [63]. Enterococcus spp. can grow in a broad pH range of 4.6–9.9, although its optimal growth occurs at pH 7.5 [64]. Lactobacillus spp. grow in a pH range of 4.0–6.5, with optimal growth at pH 5.8–6.0 [65, 66]. Lactococcus spp. can grow in a pH range of 4.0–7.0, with optimal growth at pH 6.3 [67]. Streptococcus spp. grow in a pH range of 4.5–7.0 [68], with optimal growth at pH 6.5 [65]. Thus, fresh fermented dairy products have a suitable pH range for probiotics to grow. A slightly to moderately acidic pH maintains the stability and viability of probiotics in fermented dairy products during storage.

3.3 Raw material (Bovine milk)

Table 5 presents viability data for both storage periods. All 11 products stored for 14 or 15 days met the minimum probiotic content standard (10⁶ CFU/g). Fifteen out of 16 products stored for 28 or 30 days also met the standard. Most fermented dairy products in Table 5 can be considered probiotic products. Changes were observed in most probiotics in Table 5, as probiotic counts decreased during storage for all types of bovine milk. For 14 or 15 days of storage, nine out of 11 products showed a decrease in probiotic counts. For 28 or 30 days of storage, 15 out of 16 products also experienced a decline in probiotic counts. In summary, all types of bovine milk met the standard for probiotic viability, but cell counts decreased during storage. Therefore, bovine milk variations do not impact probiotic stability or viability in fermented dairy products.

Table 5: Effect of milk type on probiotics stability and viability in fermented dairy products during storage

Product		Probiotic	Viability (log10 CFU/g)			Stability (%)		Reference
Milk	Typea		Before Storage	14/15th Day	28/30th Day	14/15th Day	28/30th Day
Cow	Cheese	Lactobacillus sp.	9.70	9.72	8.26	-	-	[33]
	Yoghurt	Lactobacillus sp.	7.69	-	7.11	-	-	[43]
	Yoghurt	Starter: L. bulgaricus S. thermophilus	8.77 8.37	8.12 8.09	7.44 7.38	- -	- -	[45]
	Yoghurt	Combination (Lactobacillus sp., Streptococcus sp., Bifidobacterium sp.)	10.00	-	6.00	-	-	[46]
Lamb	Yoghurt	Combination (Lactobacillus sp., Streptococcus sp., Bifidobacterium sp.)	10.00	-	9.00	-	-	[46]
Goat	Yoghurt	Combination (Lactobacillus sp., Streptococcus sp., Bifidobacterium sp.)	10.00	-	8.00	-	-	[46]
	Cheese	Lactobacillus sp.	8.50	8.30	8.30	-	-	[22]
	Yoghurt	Lactobacillus sp.	7.15	7.09	6.76	-	-	[37]
	Yoghurt	Starter: L. bulgaricus S. thermophilus	8.00 9.00	8.75 8.80	8.00 8.54	- -	- -	[44]
Buffalo	Cheese	Lactobacillus sp.	9.24	8.16	7.24	-	-	[24]
	Yoghurt	Lactobacillus sp.	7.26	-	5.17	-	-	[43]
Yak	Yoghurt	Lactobacillus sp.	8.85	8.26	7.36	-	-	[45]
	Yoghurt	Starter: L. bulgaricus S. thermophilus	8.83 8.78	8.32 8.23	7.62 7.64	- -	- -	[45]

^a) Storage temperature at 4 °C

3.4 Probiotic genus

Regardless of genus variations, most fermented dairy products in Table 6 can be considered probiotic products. Probiotic viability data for 14 or 15 days of storage showed that 16 out of 17 samples met the minimum content standard (10⁶ CFU/g). For 28 or 30 days of storage, 17 out of 20 samples also met the standard. However, based on the data in Table 6, most probiotics in fermented dairy products exhibited changes, with decreased probiotic cell counts during storage for Bifidobacterium spp., Lactobacillus spp., Lactococcus spp., and Streptococcus spp. For 14 or 15 days of storage, 11 out of 16 products showed a decrease in probiotic counts. For 28 or 30 days of storage, 17 out of 19 products also experienced a decline. However, Enterococcus spp. showed a linear increase in probiotic counts during storage for up to 28 or 30 days. This result may be due to the characteristics of Enterococcus sp., which can grow in a wide range of pHs (4.6–9.9) [61] and can withstand pasteurization temperatures [69, 70]. Enterococcus spp. is a probiotic because it helps maintain gut homeostasis [71] and is resistant to bile salts, allowing it to colonize the colon [72]. However, Enterococcus spp. can also act as an opportunistic pathogen by taking advantage of a weakened immune system to proliferate outside the colon [73].

All probiotic genera in the fermented dairy products met the viability standard during storage. Regarding stability, Bifidobacterium spp., Lactobacillus spp., Lactococcus spp., and Streptococcus spp. showed decreased cell counts, whereas Enterococcus spp. exhibited increased cell counts during storage. Hence, the probiotic genus affects stability, but does not impact viability in fermented dairy products. Many studies revealed that probiotic strains from the genus Bifidobacterium exhibited the lowest stability when are compared to strains from the genus Lactobacillus and Enterococcus due to the sensitivity of Bifidobacterium to the dissolved oxygen and low pH in fermented dairy products [74].

Table 6: Effect of probiotic genus on probiotics stability and viability in fermented dairy products during storage

Probiotic		Producta, b	Viability (log10 CFU/g)			Stability (%)		Reference
Genus	Species		Before Storage	14/15th Day	28/30th Day	14/15th Day	28/30th Day
Bifidobacterium	B. adolescentis	Yoghurt (-18oC)	8.41	8.40	8.15	99.8	96.9	[36]
	B. bifidum	Yoghurt	8.25	6.10	3.10	-	-	[35]
	B. infantis	Yoghurt (-18oC)	8.44	8.36	8.23	99.1	97.5	[36]
	B. lactis	Yoghurt	7.90	-	7.76	-	-	[43]
Enterococcus	E. faecium	Cheese	8.69	8.72	11.03	-	-	[30]
Lactobacillus	L. acidophilus	Yoghurt	7.69	-	7.11	-	-	[43]
	L. agilis	Cheese	9.82	6.52	5.91	-	-	[27]
	L. brevis	Cheese	8.62	-	8.70	-	-	[25]
	L. casei	Cheese	8.41	8.49	7.71	-	-	[30]
	L. delbrueckii Subsp. bulgaricus	Yoghurt	8.77	8.12	7.44	-	-	[45]
	L. fermentum	Yoghurt	8.43	7.67	6.84	-	-	[45]
	L. helveticus	Cheese	9.32	7.78	6.61	-	-	[27]
	L. mucosae	Cheese (goat milk)	8.28	8.59	8.72	-	-	[23]
	L. paracasei	Yoghurt	7.42	7.04	6.93	-	-	[48]
	L. plantarum	Cheese	8.90	9.23	8.56	-	-	[31]
	L. reuteri	Cheese	9.70	9.72	8.26	-	-	[33]
	L. rhamnosus	Cheese	8.79	8.97	8.46	-	-	[30]
	L. salivarius	Cheese	9.77	5.79	4.98	-	-	[27]
Lactococcus.	L. lactis	Cheese (12oC)	9.58	9.36	8.73	-	-	[26]
Streptococcus	S. thermophilus	Yoghurt	8.37	8.09	7.38	-	-	[45]

^a) Cow milk (unless stated otherwise), b) Storage temperature at 4 °C (unless stated otherwise)

3.5 Probiotic microencapsulation

The viability data in Table 7 for 14 or 15 days of storage indicate that 15 out of 16 samples met the minimum probiotic content standard (10⁶ CFU/g) for fermented dairy products. The data for 28 or 30 days of storage show that 11 out of 14 samples also met the standard. Most fermented dairy products in Table 7 can thus be considered probiotic products. Probiotic viability data for encapsulated cells, compared to free cells, revealed that almost all microencapsulation materials resulted in higher probiotic viability than that of free cells in fermented dairy products during storage. Encapsulation systems protect cells from damaging environmental factors, such as high humidity, oxygen, acid, and heat [75]. Furthermore, encapsulated probiotics have a slower metabolism because of the protective layer, resulting in a slower pH drop and lower post-acidification activity than that of free cells during storage [76]. However, skim milk as an encapsulation material resulted in lower probiotic viability than that of free cells after 28 or 30 days of storage. Dantas et al. [42] attributed this result to the use of lactose-free skim milk, which reduces the effectiveness of lactose metabolism as a source of energy, causing a faster decline in cell counts than that observed in free cells during storage.

Table 7: Effect of probiotic microencapsulation material on probiotics stability and viability in fermented dairy products during storage

Probiotic		Producta, b, c	Viability (log10 CFU/g)			Stability (%)		Reference
Encapsulation Material	Genus		Before Storage	14/15th Day	28/30th Day	14/15th Day	28/30th Day
Alginate	Lactobacillus	Cheese	8.19(FC) 7.50(EC)	8.05(FC) 6.93(EC)	7.50(FC) 7.08(EC)	-	-	[32]
	Lactobacillus	Cheese	7.24(FC) 7.44(EC)	8.05(FC) 8.37(EC)	8.23(FC) 8.33(EC)	-	-	[28]
	Bifidobacterium	Yoghurt	8.25(FC) 8.60(EC)	6.10(FC) 8.30(EC)	3.10(FC) 7.40(EC)	-	-	[35]
Alginate + glycerol	Bifidobacterium	Yoghurt	9.50(EC)	-	5.90(EC)	-	-	[51]
Alginate + carrageenan	Bifidobacterium	Yoghurt	9.50(EC)	-	6.70(EC)	-	-	[51]
Alginate + xanthan gum + β-cyclodextrin	Bifidobacterium	Yoghurt (-18oC)	9.43(EC)	9.56(EC)	9.63(EC)	-	-	[34]
Arabic gum+ inulin	Bifidobacterium	Yoghurt	6.85(FC) 6.65(EC)	6.44(FC) 6.72(EC)	6.72(FC) 6.52(EC)	-	-	[52]
Protein whey	Bifidobacterium	Yoghurt	8.25(FC) 8.55(EC)	6.10(FC) 8.40(EC)	3.10(FC) 7.70(EC)	-	-	[35]
Protein whey + alginate	Bifidobacterium	Yoghurt	8.27(FC) 8.53(EC)	4.40(FC) 5.57(EC)	4.11(FC) 5.36(EC)	53.2(FC) 65.3(EC)	49.7(FC) 62.8(EC)	[41]
Protein whey + arabic gum	Lactobacillus	Yoghurt	7.42(FC) 7.36(EC)	7.04(FC) 7.25(EC)	6.93(FC) 7.34(EC)	-	-	[48]
Protein whey + chitosan	Bifidobacterium	Yoghurt	8.27(FC) 8.81(EC)	4.40(FC) 6.45(EC)	4.11(FC) 5.39(EC)	53.2(FC)-73.2(EC)	49.7(FC) 61.2(EC)	[41]
Protein whey + pectin	Lactobacillus	Yoghurt	8.18(FC) 7.25(EC)	8.04(FC) 7.14(EC)	7.75(FC) 7.06(EC)	98.3(FC) 98.5(EC)	94.7(FC) 97.4(EC)	[47]
Skim milk	Bifidobacterium	Yoghurt	8.89(FC) 8.87(EC)	8.49(FC) 8.50(EC)	8.22(FC) 8.06(EC)	95.5(FC) 95.8(EC)	92.5(FC)90.9(EC)	[42]
Water-in-oil-water (W1/O/W2)	Lactobacillus	Yoghurt	9.05(FC) 9.25(EC)	7.00(FC) 8.05(EC)	6.30(FC) 7.65(EC)	-	-	[50]
Xanthan- chitosan (XC)	Bifidobacterium	Yoghurt	8.40(FC) 8.50(EC)	4.85(FC) 7.95(EC)	-	-	-	[38]
	Lactobacillus	Yoghurt	8.45(FC) 8.45(EC)	6.55(FC) 7.75(EC)	-	-	-	[39]
Xanthan-chitosan-xanthan (XCX) double layer	Bifidobacterium	Yoghurt	8.40(FC) 8.55(EC)	4.85(FC) 7.75(EC)	-	-	-	[38]
	Lactobacillus	Yoghurt	8.45(FC) 8.20(EC)	6.55(FC) 7.80(EC)	-	-	-	[39]

^a) Lactobacillus sp. probiotics, ^b) Cow milk, ^c) Storage temperature at 4–5 °C (unless stated otherwise); (FC) Free cells, (EC) Encapsulated cells

Most samples in Table 7 showed a decrease in probiotic cell counts during storage, regardless of microencapsulation materials. However, encapsulation with alginate + xanthan gum + β-cyclodextrin resulted in a linear increase in probiotic counts during storage for up to 28 or 30 days. This increase may also be due to the storage temperature, as frozen yogurt was stored at −18 °C [34], whereas other products in Table 7 were stored refrigerated at 4–5 °C. The increasing cell counts in frozen yogurt during storage also support the use of β-cyclodextrin as an encapsulation material. β-cyclodextrin acts as a prebiotic, serving as a carbon source, being lipophilic, and acting as a thermo protector, thereby enhancing or at least maintaining probiotic growth during storage [77, 78].

All microencapsulation materials met the probiotic viability standard during storage. Encapsulated probiotics exhibited greater viability during storage than free cells, except when using skim milk as an encapsulant, which resulted in lowered probiotic cell counts. Moreover, decreased cell counts were observed for all microencapsulation materials during storage at 4−5 °C, except for alginate + xanthan gum + β-cyclodextrin, which resulted in increased cell counts during storage at −18 °C. Therefore, the microencapsulation material affects the stability of probiotics but not their viability in fermented dairy products.

3.6 Storage temperature

Viability data for both storage periods show that the minimum standard probiotic content (10⁶ CFU/g) was met for storage temperatures of −18, 4, 5, 8, and 12 °C (Table 8). However, samples stored at 25 °C for more than 14 or 15 days, and those stored at 28 °C and 37 °C for any duration, did not meet the standard and cannot be considered probiotic products. The low probiotic viability of these samples can be explained by the high temperatures of storage, which are near the optimum temperature for probiotic growth (37–43 °C) [79], thus boosting cell metabolism and leading to the early death of probiotics [80]. Exposure to high temperatures during storage also results in dehydration and osmotic stress, damaging the structure of probiotic cells, including the cell membrane, ribosomes, DNA, and RNA [81].

As shown in Table 8, most probiotic cell counts in fermented milk products decreased at all storage temperatures. For 14 or 15 days of storage, 10 out of 16 samples showed a decrease in probiotic counts. For 28 or 30 days of storage, 13 out of 14 products also exhibited a decrease. At storage temperatures of −18, 4, and 5 °C, non-significant decreases in cell counts were observed. However, at 8, 12, 25, 28, and 37 °C, cell counts showed significant decreases during storage. A storage temperature of −18 °C results in all probiotics being in a dormant state because only tightly bound water (aw < 0.3) is available, slowing cell metabolism and respiration and thus stabilizing probiotic counts during storage [82]. On the other hand, a storage temperature of 4–5 °C slows the probiotic growth rate by inhibiting enzymatic, chemical, and biochemical reactions in cells, keeping the probiotics in a stationary phase. Thus, the probiotic counts remain stable or even increase during cold storage [79].

Storage temperatures of −18, 4, 5, 8, and 12 °C met the probiotic viability standard. However, storage at 25, 28, and 37 °C did not met the probiotic viability standard. Probiotic products stored at −18, 4, and 5 °C showed stable counts, with non-significant decreases. By contrast, those stored at 8, 12, 25, 28, and 37 °C exhibit significant decreases in probiotic cell counts. Therefore, the storage temperature affects the stability and viability of probiotics in fermented milk products.

Table 8: Effect of storage temperature & packaging type on probiotics stability and viability in fermented dairy products during storage

Storage Temperature (oC)	Packaging	Producta, b	Viability (log10 CFU/g)			Stability (%)		Reference
			Before Storage	14/15th Day	28/30th Day	14/15th Day	28/30th Day
-18	-	Yoghurt (B)	8.34	8.25	8.11	98.9	97.2	[36]
4	Plastic without lid	Yoghurt	7.69	-	7.11	-	-	[43]
	Plastic without lid	Yoghurt	8.43	7.67	6.84	-	-	[45]
	Plastic pouch	Cheese	9.00	-	8.90	-	-	[21]
	Plastic pouch	Cheese	9.70	9.72	8.26	-	-	[33]
	Plastic with lid	Cheese	8.90	9.23	8.56	-	-	[31]
	Plastic with aluminium foil lid	Cheese	7.24	8.05	8.23	-	-	[28]
	-	Yoghurt (B)	8.40	4.85	-	-	-	[38]
	-	Yoghurt	8.45	6.55	-	-	-	[39]
	Closed glass bottle	Yoghurt (goat milk)	7.15	7.09	6.76	-	-	[37]
	Vacuum packaging	Cheese	8.41	8.49	7.71	-	-	[30]
5	Plastic with aluminium foil lid	Yoghurt	8.18	8.04	7.75	98.3	94.7	[47]
8	Plastic with aluminium foil lid	Cheese	8.09	8.13	6.36	-	-	[29]
12	Vacuum packaging	Cheese	8.63	8.38	8.25	-	-	[26]
25	-	Yoghurt (B)	8.15	4.20	-	-	-	[38]
	-	Yoghurt	8.45	6.50	-	-	-	[39]
28	-	Yoghurt	7.80	4.70	5.20	-	-	[40]
37	-	Yoghurt	7.70	4.60	3.40	-	-	[40]

^a) Lactobacillus sp. probiotics, ^b) Cow milk (unless stated otherwise); (B) Bifidobacterium sp. probiotics

3.7 Packaging type

The different types of packaging for fermented milk products were evaluated at a storage temperature of 4 °C (Table 8). The packaging types were divided into five categories: plastic without a lid, plastic with a lid, plastic with an aluminum foil lid, closed glass bottles, and vacuum packaging. Viability data for both storage periods (14 or 15 days and 28 or 30 days) showed that all six and eight respective samples met the minimum probiotic content standard (10⁶ CFU/g). Therefore, all the fermented milk products in Table 8, which were stored at 4 °C, can be considered probiotic products, regardless of the packaging used.

Probiotic counts during 14 or 15 days of storage varied depending on the type of packaging: a significant decrease was observed for plastic without a lid, a non-significant decrease was noticed for closed glass bottles, a significant increase was recorded for plastic with a lid or an aluminum foil lid, and a non-significant increase was seen for vacuum packaging. The significant drop in cell counts observed for plastic without a lid was attributed to direct exposure to oxygen from the environment, as oxygen inhibits the anaerobic metabolism (and thus enzymatic reactions) of probiotic cells [43]. The significant increase in cell counts for products stored in plastic with a lid or an aluminum foil lid was due to the anaerobic environment produced inside the packaging. Furthermore, the permeability of plastic allows the entry of water vapor to support the metabolism of probiotics [79]. On the other hand, the non-significant decrease and increase in cell counts recorded for closed glass bottles and vacuum packaging, respectively, may be due to the low level of oxygen and water vapor exposure. Glass packaging has lower permeability than plastic, and thus enhances the stability of the product [83].

Probiotic counts decreased for products stored in four out of five types of packaging during 28 or 30 days: plastic without a lid, plastic with a lid, closed glass bottles, and vacuum packaging. This drop in cell counts is likely the result of a lowered pH value, oxygen exposure, and the accumulation of organic acids caused by post-acidification activity (i.e., the production of acid as a result of the continuous metabolism of probiotics during storage) [57, 61, 62]. By contrast, a linear increase in cell counts during storage for up to 28 or 30 days was observed for products stored in plastic with an aluminum foil lid, suggesting that the permeable plastic container allows the entry of water vapor to sustain probiotic metabolism. The aluminum foil lid exhibits low permeability and is also lightproof and heat-resistant; thus, together with cold storage, it helps delay the accumulation of acid metabolites in the product [84, 85].

Every type of packaging met the probiotic viability standard for fermented milk products during storage. Probiotic counts in products stored in plastic without a lid, plastic with a lid, closed glass bottles, and vacuum packaging decreased. By contrast, those stored in plastic with an aluminum foil lid showed increased probiotic counts. Thus, the type of packaging affects the stability, but not the viability, of probiotics in fermented dairy products.

4. Conclusion

The stability of probiotics in fermented dairy products (cheese and yogurt) during storage is affected by the probiotic genus, microencapsulation material, storage temperature, product form and packaging type. Furthermore, product form and storage temperature affect the viability of probiotics in fermented dairy products during storage. In most cases and until the 30^th day of storage, the stability (i.e., the numbers) of most probiotics decreased. However, most products met the minimum standard (10⁶ CFU/g) for probiotic viability to be considered functional foods with health benefits. Future research may include advanced studies on the influence of the type of packaging used during fermented milk product storage and an investigation of probiotic stability in those products during storage.

CRediT authorship contribution statement

Muhammad Zukhrufuz Zaman: Conceptualization, Methodology, Software, Validation, Formal analysis, Writing- original draft, Writing- review & editing, Visualization, Supervision, Funding acquisition. Raifadila Bariza Erwadi: Conceptualization, Methodology, Validation, Formal analysis, Investigation, Writing- original draft, Visualization. Danar Praseptingga: Conceptualization, Methodology, Validation, Writing- review & editing, Supervision. Asri Nursiwi: Methodology, Validation, Writing- review & editing.

Acknowledgements

This study was partially supported by Universitas Sebelas Maret through PKGR-UNS Research Scheme under contract number: 371/UN27.22/PT.01.03/2025

References

• [1]  FAO/WHO (2001) Joint FAO/WHO Expert Consultation on evaluation of health and nutritional properties of probiotics. In Food including powder milk with live lactic acid bacteria. Cordoba. https://openknowledge.fao.org/handle/20.500.14283/y6398e (Accessed on 15 August 2025)
• [2]  Mani-López E, Palou E and López-Malo A (2014) Probiotic viability and storage stability of yoghurts and fermented milks prepared with several mixtures of lactic acid bacteria. J. Dairy Sci., 97(5): 2578–2590. https://doi.org/10.3168/jds.2013-7551
• [3]  Gogineni VK, Morrow LE, Gregory PJ and Malesker MA (2013) Probiotics: history and evolution. J. Infect. Dis. Prev. Med., 1(2): 1–7. https://doi.org/10.4172/2329-8731.1000107
• [4]  Diplock AT, Agget PJ, Ashwell M, Bornet F, Fern EB and Roberfroid MB (1999) Scientific concepts of functional foods in Europe: Consensus document. Brit. J. Nutr., 81(1): S1–S27. https://doi.org/10.1017/S0007114599000471
• [5]  Shiby VK and Mishra HN (2013) Fermented milks and milk products as functional foods-A review. Crit. Rev. Food Sci. Nutr., 53(5): 482–496. https://doi.org/10.1080/10408398.2010.547398
• [6]  Guetouache M, Guessas B and Medjekal S (2014) Composition and nutritional value of raw milk. J. Issues Biol. Sci. Pharm. Res., 2(10): 115–122. http://dx.doi.org/10.15739/ibspr.005
• [7]  Pitino I, Randazzo CL, Cross KL, Parker ML, Carlo Bisignano C, Wickham MSJ, Mandalari G and Caggia C (2012) Survival of Lactobacillus rhamnosus strains inoculated in cheese matrix during simulated human digestion. Food Microb., 31(1): 57–63. https://doi.org/10.1016/j.fm.2012.02.013
• [8]  FAO/WHO (2003) Joint FAO/WHO Codex Alimentarius Commision. Milk and Milk Products: Fermented Milk. CODEX STAN 243–2003. Rome. https://www.fao.org/fao-who-codexalimentarius/sh-proxy/en/?lnk=1&url=https%253A%252F%252Fworkspace.fao.org%252Fsites%252Fcodex%252FStandards%252FCXS%2B243-2003%252FCXS_243e.pdf (Accessed on 15 Auugust 2025)
• [9]  Khorshidian N, Yousefi M and Mortazavian AM (2020) Fermented milk: The most popular probiotic food carrier. Adv. Food Nutr. Res., 94: 91–114. https://doi.org/10.1016/bs.afnr.2020.06.007
• [10]  Karimi R, Mortazavian AM and Da Cruz AG (2011) Viability of probiotic microorganisms in cheese during production and storage: a review. Dairy Sci. Tech., 91(3): 283–308. https://doi.org/10.1007/s13594-011-0005-x
• [11]  Tripathi MK and Giri SK (2014) Probiotic functional foods: Survival of probiotics during processing and storage. J. Funct. Foods, 9: 225–241. https://doi.org/10.1016/j.jff.2014.04.030
• [12]  Vinderola G, Binetti A, Burns P and Reinheimer J (2011) Cell viability and functionality of probiotic bacteria in dairy products. Front. Microb., 2(70): 1–6. https://doi.org/10.3389/fmicb.2011.00070
• [13]  Corona‐Hernandez RI, Alvarez‐Parrilla E., Lizardi‐Mendoza J, Islas‐Rubio AR, de la Rosa LA and Wall‐Medrano A (2013) Structural stability and viability of microencapsulated probiotic bacteria: a review. Compr. Rev. Food Sci. Food Saf., 12(6): 614–628. https://doi.org/10.1111/1541-4337.12030
• [14]  Mengist W, Soromessa T and Legese G (2020) Method for conducting systematic literature review and meta-analysis for environmental science research. MethodsX, 7: 100777. https://doi.org/10.1016/j.mex.2019.100777
• [15]  dos Santos KMO, Vieira ADS, Buriti FCA, do Nascimento JCF, de Melo MES, Bruno LM et al. (2015) Artisanal coalho cheeses as source of beneficial Lactobacillus plantarum and Lactobacillus rhamnosus strains. Dairy Sci. Tech., 95(2): 209–230. https://doi.org/10.1007/s13594-014-0201-6
• [16]  Amo IF, Erkoyuncu JA, Roy R, Palmarini R and Onoufriou D (2018) A systematic review of Augmented Reality content-related techniques for knowledge transfer in maintenance applications. Comput. Ind., 103: 47–71. https://doi.org/10.1016/j.compind. 2018.08.007
• [17]  Page MJ, McKenzie JE, Bossuyt PM, Boutron I, Hoffmann TC, Mulrow CD et al. (2021) The PRISMA 2020 statement: an updated guideline for reporting systematic reviews. Syst. Rev., 10(1): 1–11. https://doi.org/10.1136/bmj.n71
• [18]  Shelby LB and Vaske JJ (2008) Understanding meta-analysis: A review of the methodological literature. Leis. Sci., 30(2): 96–110. https://doi.org/10.1080/01490400701881366
• [19]  Barker TH, Habibi N, Aromataris E, Stone JC, Leonardi-Bee J, Sears K et al. (2024) The revised JBI critical appraisal tool for the assessment of risk of bias quasi-experimental studies. JBI Evid. Synth., 22(3): 378–388. https://doi.org/10.11124/jbies-23-00268
• [20]  McGuinness LA and Higgins JPT (2020) Risk-of-bias VISualization (robvis): An R package and Shiny web app for visualizing risk-of-bias assessments. Res. Syn. Meth., 1–7. https://doi.org/10.1002/jrsm.1411
• [21]  Cichosz G, Aljewicz M and Nalepa B (2014) Viability of the Lactobacillus rhamnosus HN001 probiotic strain in Swiss‐and Dutch‐type cheese and cheese‐like products. J. Food Sci., 79(6): M1181–M1188. https://doi.org/10.1111/1750-3841.12458
• [22]  Martins IBA, Deliza R, dos Santos KMO, Walter EHM, Martins JM and Rosenthal A (2018) Viability of probiotics in goat cheese during storage and under simulated gastrointestinal conditions. Food Bioprocess Technol., 11: 853–863. https://doi.org/10.1007/s11947-018-2060-2
• [23]  Moraes GMD, dos Santos KMO, de Barcelos SC, Lopes SA and do Egito AS (2018) Potentially probiotic goat cheese produced with autochthonous adjunct culture of Lactobacillus mucosae: Microbiological, physicochemical and sensory attributes. LWT- Food Sci. Tech., 94: 57–63. https://doi.org/10.1016/j.lwt.2018.04.028
• [24]  Mushtaq M, Gani A, Masoodi FA and Ahmad M (2016) Himalayan cheese (kalari/kradi) - Effect of different probiotic strains on oxidative stability, microbiological, sensory and nutraceutical properties during storage. LWT-Food Sci. Tech., 67: 74–81. https://doi.org/10.1016/j.lwt.2015.11.039
• [25]  Łepecka A, Okoń A, Szymański P, Zielińska D, Kajak-Siemaszko K, Jaworska D et al. (2021) The use of unique, environmental lactic acid bacteria strains in the traditional production of organic cheeses from unpasteurized cow’s milk. Molecules, 27(3): 1097. https://doi.org/10.3390/molecules27031097
• [26]  Chaves KS and Gigante ML (2016) Prato cheese as suitable carrier for Lactobacillus acidophilus La5 and Bifidobacterium Bb12. Int. Dairy J., 52: 10–18. https://doi.org/10.1016/j.idairyj.2015.08.009
• [27]  Ehsani A, Hashemi M, Afshari A and Aminzare M (2018) Probiotic white cheese production using coculture with Lactobacillus species isolated from traditional cheeses. Vet. World, 11(5): 726–730. https://doi.org/10.14202/vetworld.2018.726-730
• [28]  Nejati R, Gheisari HR, Hosseinzadeh S and Behbod M (2016) Viability of encapsulated Lactobacillus acidophilus (LA‐5) in UF cheese and its survival under in vitro simulated gastrointestinal conditions. Int. J. Dairy Technol., 70(1): 77–83. https://doi.org/10.1111/1471-0307.12312
• [29]  Moghari AA, Razavi SH, Ehsani MR and Mousavi M (2014) Development and critical quality characterization of functional UF‐Feta cheese by incorporating probiotic bacteria. J. Food Process. Preserv., 39(6): 599–605. https://doi.org/10.1111/jfpp.12266
• [30]  Anihouvi ES and Kesenkaş H (2022) Wagashi cheese: Probiotic bacteria incorporation and significance on microbiological, physicochemical, functional and sensory properties during storage. LWT-Food Sci. Technol., 155: 112933. https://doi.org/10.1016/j.lwt.2021.112933
• [31]  Tologana RD, Wikandari R, Rahayu ES, Suroto DA and Utami T (2022) Correlation between the chemical, microbiological and sensory characteristics of cream cheese using a mixed and single probiotic culture. J. Food Sci. Technol., 60(1): 181–189. https://doi.org/10.1007/s13197-022-05603-0
• [32]  Ningtyas DW, Bhandari B, Bansal N and Prakash S (2019) The viability of probiotic Lactobacillus rhamnosus (non-encapsulated and encapsulated) in functional reduced-fat cream cheese and its textural properties during storage. Food Control, 100: 8–16. https://doi.org/10.1016/j.foodcont.2018.12.048
• [33]  Speranza B, Campaniello D, Monacis N, Bevilacqua A, Sinigaglia M and Corbo, MR (2018) Functional cream cheese supplemented with Bifidobacterium animalis subsp. lactis DSM 10140 and Lactobacillus reuteri DSM 20016 and prebiotics. Food Microbiol., 72: 16–22. https://doi.org/10.1016/j.fm.2017.11.001
• [34]  Hain AB, Gomes IT, Gomes RG and Bergamasco RDC (2021) Effect of β-cyclodextrin on the survival of alginate–xanthan microencapsulated Bifidobacterium-BB12 in simulated digestive conditions and frozen yogurt. J. Culin. Sci. Technol., 20(6): 551–562. https://doi.org/10.1080/15428052.2021.1884997
• [35]  Afzaal M, Saeed F, Hussain M, Ismail Z, Siddeeg A, Ammar AF and Aljobair MO (2022) Influence of encapsulation on the survival of probiotics in food matrix under simulated stress conditions. Saudi J. Biol. Sci., 29(9): 103394. https://doi.org/10.1016/j.sjbs.2022.103394
• [36]  Abdelazez A, Muhammad Z, Zhang QX, Zhu ZT, Abdelmotaal H, Sami R and Meng MC (2017) Production of a functional frozen yogurt fortified with Bifidobacterium spp. BioMed Res. Int., 2017: 1–10. https://doi.org/10.1155/2017/6438528
• [37]  Menezes MUFO, Bevilaqua GC, Ximenes GNDC, Andrade SAC, Kasnowski MC and Barbosa NMDSC (2022) Viability of Lactobacillus acidophilus in whole goat milk yogurt during fermentation and storage stages: a predictive modeling study. Food Sci. Technol., 42: e50922. https://doi.org/10.1590/fst.50922
• [38]  Chen L, Yang T, Song Y, Shu G and Chen, H. (2017). Effect of xanthan-chitosan-xanthan double layer encapsulation on survival of Bifidobacterium BB01 in simulated gastrointestinal conditions, bile salt solution and yogurt. LWT-Food Sci. Technol., 81: 274–280. https://doi.org/10.1016/j.lwt.2017.04.005
• [39]  Shu G, He Y, Chen L, Song Y, Meng J and Chen H (2017). Microencapsulation of Lactobacillus acidophilus by xanthan-chitosan and its stability in yoghurt. Polymers, 9(12): 733. https://doi.org/10.3390/polym9120733
• [40]  Chen SU, Chen L, Chen L, Ren X, Ge H, Li B et al. (2018) Potential probiotic characterization of Lactobacillus reuteri from traditional Chinese highland barley wine and application for room-temperature-storage drinkable yogurt. J. Dairy Sci., 101(7): 5780–5788. https://doi.org/10.3168/jds.2017-14139
• [41]  Yasmin HM, Zahoor T, Sagheer A, Nadeem M, Khaliq A, Iqbal R et al. (2018) Assessment of antagonistic activity of free and encapsulated Bifidobacterium bifidum against Salmonella. J. Food Saf., 38(6): e12546. https://doi.org/10.1111/jfs.12546
• [42]  Dantas A, Verruck S, Canella MHM, Hernandez E and Prudencio ES (2021) Encapsulated Bifidobacterium BB-12 addition in a concentrated lactose-free yogurt: Its survival during storage and effects on the product's properties. Food Res. Int., 150: 110742. https://doi.org/10.1016/j.foodres.2021.110742
• [43]  Nguyen HTH, Ong L, Lefèvre C, Kentish SE and Gras SL (2013) The microstructure and physicochemical properties of probiotic buffalo yoghurt during fermentation and storage: a comparison with bovine yoghurt. Food Bioprocess Technol., 7: 937–953. https://doi.org/10.1007/s11947-013-1082-z
• [44]  Mahmoudi I, Telmoudi A, Ben Moussa O, Chouaibi M and Hassouna, M (2021) Quality characteristics of goat yogurt containing Lactobacillus probiotic bacteria. J. Agric. Sci. Technol., 23(1): 83–96.
• [45]  Zhang X, Yang J, Zhang C, Chi H, Zhang C, Zhang J et al. (2022) Effects of Lactobacillus fermentum HY01 on the quality characteristics and storage stability of yak yogurt. J. Dairy Sci., 105(3): 2025–2037. https://doi.org/10.3168/jds.2021-20861
• [46]  Ospanov A, Velyamov S, Makeeva R, Tlevlessova D and Tastanova R (2022) Development of probiotic yogurt from small cattle milk. East.-Eur. J. Enterp. Technol., 118(11): 53–59. https://doi.org/10.15587/1729-4061.2022.261574
• [47]  Ribeiro MCE, Chaves KS, Gebara C, Infante FN, Grosso CR and Gigante ML (2014) Effect of microencapsulation of Lactobacillus acidophilus LA-5 on physicochemical, sensory and microbiological characteristics of stirred probiotic yoghurt. Food Res. Int., 66: 424–431. https://doi.org/10.1016/j.foodres.2014.10.019
• [48]  Bosnea LA, Moschakis T and Biliaderis CG (2016). Microencapsulated cells of Lactobacillus paracasei subsp. paracasei in biopolymer complex coacervates and their function in a yogurt matrix. Food Funct., 8(2): 554–562. https://doi.org/10.1039/C6FO01019A
• [49]  Jouki M, Khazaei N, Rezaei F and Taghavian-Saeid R (2021) Production of synbiotic freeze-dried yoghurt powder using microencapsulation and cryopreservation of L. plantarum in alginate-skim milk microcapsules. Int. Dairy J., 122: 105133. https://doi.org/10.1016/j.idairyj.2021.105133
• [50]  Kadri HE, Lalou S, Mantzouridou F and Gkatzionis K (2018) Utilisation of water-in-oil-water (W1/O/W2) double emulsion in a set-type yogurt model for the delivery of probiotic Lactobacillus paracasei. Food Res. Int., 107: 325–336. https://doi.org/10.1016/j.foodres.2018.02.049
• [51]  Frakolaki G, Kekes T, Lympaki F, Giannou V and Tzia C (2021) Use of encapsulated Bifidobacterium animalis subsp. lactis through extrusion or emulsification for the production of probiotic yogurt. J. Food Process Eng., 45(7): e13792. https://doi.org/10.1111/jfpe.13792
• [52]  Pinto SS, Fritzen-Freire CB, Dias CO and Amboni RD (2019) A potential technological application of probiotic microcapsules in lactose-free Greek-style yoghurt. Int. Dairy J., 97: 131–138. https://doi.org/10.1016/j.idairyj.2019.05.009
• [53]  Ying DY, Phoon MC, Sanguansri L, Weerakkody R, Burgar I and Augustin MA (2010) Microencapsulated Lactobacillus rhamnosus GG powders: Relationship of powder physical properties to probiotic survival during storage. J. Food Sci., 75(9): E588–E595. https://doi.org/10.1111/j.1750-3841.2010.01838.x
• [54]  Shah NP and Ravula RR (2000) Influence of water activity on fermentation, organic acids production and viability of yogurt and probiotic bacteria. Aust. J. Dairy Technol., 55(3): 127–131.
• [55]  Chávez BE and Ledeboer AM (2007) Drying of probiotics: Optimization of formulation and process to enhance storage survival. Dry. Technol., 25(7-8): 1193–1201. https://doi.org/10.1080/07373930701438576
• [56]  Poddar D, Das S, Jones G, Palmer J, Jameson GB, Haverkamp RG and Singh H (2014) Stability of probiotic Lactobacillus paracasei during storage as affected by the drying method. Int. Dairy J., 39(1): 1–7. https://doi.org/10.1016/j.idairyj.2014.04.007
• [57]  Shah NP (2000) Probiotic bacteria: Selective enumeration and survival in dairy foods. J. Dairy Sci., 83(4): 894–907. https://doi.org/10.3168/jds.S0022-0302(00)74953-8
• [58]  Saccaro DM, Tamime AY, Pilleggi A and Oliveira MN (2009) The viability of three probiotic organisms grown with yoghurt starter cultures during storage for 21 days at 4 degrees C. Int. J. Dairy Technol., 62(3): 397–404. https://doi.org/10.1111/j.1471-0307.2009.00497.x
• [59]  Ozer BH and Kirmaci HA (2010) Functional milks and dairy beverages. Int. J. Dairy Technol., 63(1): 1–15. https://doi.org/10.1111/j.1471-0307.2009.00547.x
• [60]  Marafon AP, Sumi A, Alcantara MR, Tamime AY and de Oliveira MN (2011) Optimization of the rheological properties of probiotic yoghurts supplemented with milk proteins. LWT-Food Sci. Technol., 44(2): 511–519. https://doi.org/10.1016/j.lwt.2010.09.005
• [61]  Machado TADG, de Oliveira MEG, Campos MIF, de Assis POA, de Souza EL, Madruga MS et al. (2017) Impact of honey on quality characteristics of goat yoghurt containing probiotic Lactobacillus acidophilus. LWT-Food Sci. Technol., 80: 221–229. https://doi.org/10.1016/j.lwt.2017.02.013
• [62]  Olfa BM, Marwa M, Moncef C, Mouna B and Mnasser H (2019) The combined effect of phytosterols and lactulose supplementation on yoghurt quality. J. Food Nutr. Res., 7(4): 261–269. https://doi.org/10.12691/jfnr-7-4-2
• [63]  Ruiz L, Ruas-Madiedo P, Gueimonde M, Reyes-Gavilán CGDL, Margolles A and Sánchez B (2011) How do Bifidobacteria counteract environmental challenges? mechanisms involved and physiological consequences. Genes Nutr., 6(3): 307–318. https://doi.org/10.1007/s12263-010-0207-5
• [64]  Van den Berghe E, De Winter T and De Vuyst L (2006) Enterocin A production by Enterococcus faecium FAIR-E 406 is characterised by a temperature-and pH-dependent switch-off mechanism when growth is limited due to nutrient depletion. Int. J. Food Microbiol., 107(2): 159–170. https://doi.org/10.1016/j.ijfoodmicro.2005.08.027
• [65]  Rault A, Marielle B and Catherine B (2009) Fermentation pH Influences the physiological-state dynamics of Lactobacillus bulgaricus CFL1 during pH-controlled culture. Appl. Environ. Microbiol., 75(13): 4374–4381. https://doi.org/10.1128/AEM.02725-08
• [66]  Hoque MZ, Akter F, Hossain KM, Rahman MSM, Billah MM and Islam KMD (2010) Isolation, identification and analysis of probiotic properties of Lactobacillus spp. from selective regional yoghurts. World J. Dairy Food Sci., 5(1): 39–46.
• [67]  Sánchez C, Neves AR, Cavalheiro J, dos Santos MM, García-Quintáns N, López P and Santos H (2008) Contribution of citrate metabolism to the growth of Lactococcus lactis CRL264 at low pH. Appl. Environ. Microbiol., 74(4): 1136–1144. https://doi.org/10.1128/AEM.01061-07
• [68]  Hendarto DR, Handayani AP, Esterelita E and Handoko YA (2019) Biochemistry mechanism and optimization Lactobacillus bulgaricus and Streptococcus thermophilus in processing quality yoghurt. J. Sains Dasar, 8(1): 13–19. (In Indonesian with English abstract). https://doi.org/10.21831/jsd.v8i1.24261
• [69]  Giraffa G, Carminati D and Neviani E (1997) Enterococci isolated from dairy products: a review of risks and potential technological use. J. Food Prot., 60(6): 732–737. https://doi.org/10.4315/0362-028X-60.6.732
• [70]  Dapkevicius MDLE, Sgardioli B, Câmara SP, Poeta P and Malcata FX (2021) Current trends of enterococci in dairy products: A comprehensive review of their multiple roles. Foods, 10(821): 1–30. https://doi.org/10.3390/foods10040821
• [71]  Saillant V, Lipuma D, Ostyn E, Joubert L, Boussac A, Guerin H et al. (2021) A novel Enterococcus faecalis heme transport regulator (Fhtr) senses host heme to control its intracellular homeostasis. mBio, 12(1): 10–1128. https://doi.org/10.1128/mbio.03392-20
• [72]  Fisher K and Phillips C (2009) The ecology, epidemiology and virulence of Enterococcus. Microbiology, 155(6): 1749–1757. https://doi.org/10.1099/mic.0.026385-0
• [73]  Krawczyk B, Wityk P, Gałęcka M and Michalik M (2021) The many faces of Enterococcus spp. - commensal, probiotic and opportunistic pathogen. Microorganisms, 9(9): 1900. https://doi.org/10.3390/microorganisms9091900
• [74]  Vinderola CG and Reinheimer JA (1999) Culture media for the enumeration of Bifidobacterium bifidum and Lactobacillus acidophilus in the presence of yoghurt bacteria. Int. Dairy J., 9(8): 497–505. https://doi.org/10.1016/S0958-6946(99)00120-X
• [75]  Solanki HK, Pawar DD, Shah DA, Prajapati VD, Jani GK, Mulla AM and Thakar PM (2013) Development of microencapsulation delivery system for long-term preservation of probiotics as biotherapeutics agent. BioMed Res. Int., 2013(620719): 1–21. https://doi.org/10.1155/2013/620719
• [76]  Kailasapathy K (2006) Survival of free and encapsulated probiotic bacteria and their effect on the sensory properties of yoghurt. LWT-Food Sci. Technol., 39(10): 1221–1227. https://doi.org/10.1016/j.lwt.2005.07.013
• [77]  Pranckute R, Kaunietis A, Kuisiene N and Citavicius D (2014) Development of synbiotics with inulin, palatinose, α-cyclodextrin and probiotic bacteria. Pol. J. Microbiol., 63(1): 33–41.
• [78]  Singh P, Medronho B, Valente AJ, Miguel MG and Lindman B (2017) Exploring the prebiotic effect of cyclodextrins on probiotic bacteria entrapped in carboxymetyl cellulose-chitosan particles. Colloids Surf. B: Biointerfaces, 168: 156–162. https://doi.org/10.1016/j.colsurfb.2017.12.014
• [79]  Putra IGPB, Duniaji AS and Nocianitri KA (2020). Viabilitas Lactobacillus sp. F213 pada minuman rice juice (Oryza sativa) selama penyimpanan suhu dingin (4^oC). Jurnal Ilmu dan Teknologi Pangan, 9(1): 46–55. (In Indonesian with English abstract)
• [80]  Oktavia HM, Kusumawati N and Kuswardhani I (2015) Effect of storage time during distribution and marketing on the viability of lactic acid bacteria and acidity level in black mulberry (Morus nigra L.) yogurt. Jurnal Teknologi Pangan dan Gizi, 14(1): 22–30. (In Indonesian with English abstract)
• [81]  Rizqiati H, Jenie BS, Nurhidayat N and Nurwitri C (2008) Survival of Lactobacillus plantarum encapsulated with skim milk and arabic gum after spray drying and its viability during storage. Animal Production, 10(3): 179–187. (In Indonesian with English abstract)
• [82]  Rodrigues VC, da Silva LGS, Simabuco FM, Venema K and Antunes AEC (2019) Survival, metabolic status and cellular morphology of probiotics in dairy products and dietary supplement after simulated digestion. J. Funct. Foods, 55: 126–134. https://doi.org/10.1016/j.jff.2019.01.046
• [83]  Dudriková E, Nagyová M and Dičáková Z. (2017) Survival of Lactobacillus bulgaricus and Bifidobacterium animalis in yoghurts made from commercial starter cultures during refrigerated storage. Potr. Slovak J. Food Sci., 11(1): 597–601. https://doi.org/10.5219/758
• [84]  Cruz AG, Faria JAF and Van Dender AG (2007) Packaging system and probiotic dairy foods. Food Res. Int., 40(8): 951–956. https://doi.org/10.1016/j.foodres.2007.05.003
• [85]  Cruz AG, Castro WF, Faria JDAF, Bolini HMA, Celeghini RMDS, Raices RSL et al. (2013) Stability of probiotic yoghurt added with glucose oxidase in plastic materials with different permeability oxygen rates during the refrigerated storage. Food Res. Int., 51(2): 723–728. https://doi.org/10.1016/j.foodres.2013.01.028