Milk and dairy products are staples of the human diet. Among them, cheese holds an important stance. Due to its biological and biochemically dynamic nature, cheese is a perishable product in need of innovative preservation methods. There have been an increasing trends for the application of natural-derived edible films/coatings and natural preservatives to extend its shelf-life. The present review focuses on the application of edible coatings and highlights their potential for prolonging the shelf-life up to one month, depending on the types of cheese, its antimicrobial type, and environmental conditions such as storage temperature.
With growing concerns over food safety, more accurate, simpler, and faster detection methods are urgently required. An online enrichment system with a molecularly imprinted polymer (MIP) for chloramphenicol (CAP) was coupled to HPLC using a flow-injection pump and developed and validated for the analysis of trace levels of CAP in milk. Compared with direct injection into the HPLC, the developed analytical method had a lower limit of detection (0.01 µg L−1) and an enrichment factor of 364 because of the specific adsorption of CAP on the MIP. The linear range of the method was 0.05 µg L−1 to 10 mg L−1 (r2 > 0.99). After online purification and enrichment, the trace amounts of CAP in milk could be quantified, with limit of detection in milk of 0.1 µg kg−1 and recoveries ranging from 82.6% to 98.1% at different spiked levels of CAP in raw milk, and commercial liquid milk.
The aim of this study was to evaluate the effect of the dried sourdoughs produced with two different fermentation methods [Spontaneous fermentation(SPF) and starter of lactic acid bacteria-added fermentation(STF)], and three different drying methods (Drying in oven;DO, Freeze drier;DFD, and Spray drier;DSD) on various quality properties of the wheat bread. The bread samples prepared by addition of the dried sourdoughs at the rates of 3%, 6% and 12%, and control bread prepared without sourdough were compared in terms of bioactivity, shelf life, physicochemical and sensory properties. The addition of the dried sourdough affected the specific volume, pH and acidity of the bread samples significantly (p < 0.05), and a slow down moisture loss occurred during shelf life. The a* value of crust, antioxidant activity, and sensory properties were improved compared to the control bread. The use of dried sourdough at the rate of 12% gave the most effective results. When the fermentation and drying methods were evaluated together, the combinations of SPF/DO, SPF/DFD and STE/DSD gave the best results.
In this study, chemical method and enzymatic method were used to extract dietary fibers (DF) from deoiled walnut residues, and the resulting fibers were named as CDF and EDF respectively. The CDF and EDF were characterized by FTIR, XRAD and SEM. Moreover, the effects of particle sizes on physiochemical properties of CDF and EDF were explored. The results indicated that enzymatic method inhibited the structural damage of walnut DF, thus increasing the external surface area of EDF. Besides, particle sizes affected the physiochemical properties (water retention capacity (WRC), oil retention capacity (ORC), water swelling capacity (WSC) and apparent viscosity) of walnut DF. Particle sizes ranged from 180 to 450 µm, CDF and EDF had higher WRC. In the particle sizes range of 125–180 µm, CDF and EDF had higher ORC and apparent viscosity. These results might provide a reference for the utilization of walnut DF in food industry.
In this study, the effects of different preparation conditions on the oxidative stability of fish oil in surimi gels were investigated. Emulsified surimi gels were prepared under different conditions (mixing speed, protein concentration, and environmental conditions) to measure the oxidative degree of fish oil during storage. The oxidation of fish oil in each type of surimi gels gradually increased within the storage period. On one hand, oxidation was suppressed when the oil particle size became smaller; lipid oxidation was also suppressed under vacuum + air as well as under vacuum. On the other hand, oil particle size decreased in the surimi gels as protein concentration increased, and oxidative stability was significantly enhanced. These results indicate that the levels of emulsification affect the oxidation level of oil in surimi gel and that complete emulsification protects fish oil from oxidation.
The effects of “setting-heating-freezing” procedure (SHF) and “setting-freezing-reheating” procedure (SFR) on the quality changes of surimi gels with or without starch after frozen storage were evaluated and compared. The samples were frozen and stored at −20°C for 28 days. Surimi gels without starch subjected to SFR showed larger ice crystals after freezing, greater microstructural damage after thawing, and higher total drip loss. In contrast, starch-surimi gels subjected to SFR showed less structural damage, smaller void size, and reduced total drip loss, attributed to the un-gelatinized starch granules before freezing and gelatinization after reheating. Changes in physical properties were related to changes in gel microstructure and starch granules, and a high gel strength was maintained in starch-surimi gels subjected to SFR after frozen storage. These results indicate that the SFR procedure can effectively reduce the quality changes in frozen starch-surimi gels.
A novel method based on a double branch deep fusion convolution neural network (DDFnet) is developed to classify dried jujubes. First, the structure of the network is designed as double branches. In one branch, the dataset of the jujubes is pre-trained with a model trained by a Squeezenet network on a large-scale ImageNet dataset. The other branch is founded on the structure of Squeezenet, which is composed of fire modules. The feature maps that are output by squeeze and expand convolution layers are fused into fusion modules. Next, a model trained on the dataset with DDFnet is used to achieve the multi-classification of jujubes. Finally, the dataset is classified by the model; it shows good performance with high accuracy rates of 99.6%, 99.8%, 98.5%, and 99.2% for the classification of plump, wizened, cracked, and defective jujubes, respectively. This research demonstrates the feasibility of DDFnet for sorting dried jujubes and enhancing product quality.
Vegetable oils have long been used in cooking. However, repeated heating at a high temperature results in the gradual deterioration of the vegetable oils through oxidative degradation of fatty acids, leading to the formation of undesirable and irritating odors (e.g., acrolein). Linolenic acid is the main source of the acrolein formed during the heating of vegetable oils. The present study has developed a method to reduce the formation of acrolein during repeated frying with vegetable oils. Electronic nose analysis showed that the formation of acrolein from low-linolenic oil such as extra virgin olive oil (EVOO) was much lower than from a linolenic-rich oil, salad oil, when frying French fries. Blending EVOO with salad oil effectively reduced the amount of acrolein formed during repeated frying. These results suggest that EVOO can be used to reduce the formation of acrolein when repeatedly heating foods in thermosensitive vegetable oils.
The fresh-cut iceberg lettuce inoculated with Listeria Monocytogenes (3 log CFU/mL) was packaged in modified atmospheres (10% CO2/10% O2, 30% CO2/10% O2, 50% CO2/10% O2) and then stored at 4°C, 8°C, 16°C, 24°C and 32°C separately. Modified Gompertz model was selected to estimate the growth rate and lag time. Results showed that the growth of L. monocytogens decreased with the increase of concentration of CO2 and revised Gompertz equation fitted the growth of L. monocytogens at different test conditions. Root Square model was chosen as a secondary model to study the effects. Mathematical evaluation was also conducted with the bias factor (Bf) and accuracy factor (Af) and residual analysis. Results showed that predictive value of the model is more accurate and reliable in level of α=0.1 and the value of Bf all is in 0.7–1.05, while the value of Af is acceptable in general.
Melanin extracted from sunflower testae was isolated, purified and the physicochemical properties, antioxidant activities, metal ion removal activity and anti-radiation were investigated. The physical and chemical characterization showed that it was acid-resistant, alkali soluble and insoluble in most of the organic solvents and distilled water and the similar redox properties to synthetic melanin from sigma. The melanin was precipitated on treatment with FeCl3, ammoniacal AgNO3, potassium ferricyanide and was bleached in the presence of oxidants and reductants. It was also confirmed as one of melanins based on the Ultraviolet visibl. (UV-vis) absorption spectroscopy, Fourier transform infrared spectrometry (FT-IR), Electron paramagnetic resonance (EPR) spectroscopy, and Scanning electron microscopy (SEM) spectroscopic techniques apart from physiochemical analysis. Elemental composition analysis revealed that the melanin was pheomelanin or allomelanins. The melanin also showed the antioxidant potential observed in the in vitro evaluation of diphenyl picryl hydrazinyl radical scavenging activity, superoxide-scavenging activity, hydroxyl-scavenging activity, reducing power, metal ion removal activity and anti-radiation activity. The activities examined indicated that melanin from sunflower testae could be considered as a novel potential antioxidant, heavy metal adsorbent, and UV protection agent. The results suggested that the melanin could potentially be used as a natural antioxidant in the food, cosmetic and other industries.
Dried jujube fruit has been wildly used as flavoring in food preparation and food industry because of its unique and exquisite flavor. However, there is limited information available on the formation and alteration of jujube flavor during drying and storage. In this study, the effects of drying and storage on the volatiles in jujube fruit were investigated by electronic nose and GC-MS. Electronic nose and GC-MS could distinguish different jujube samples clearly; the ester and aldehydes showed significant decreases during drying, while furans and pyrazines were generated and increased with heat time; the esters, aldehydes, furans and pyrazines showed significant decreases, and some of them even disappeared during storage, while acids and terpenes increased with the extension of storage. Based on the present results, furans and pyrazines, generated during drying, are the predominant components of the unique and exquisite flavor of dried jujube, and these compounds could be negatively influenced because of evaporation, oxidation and degradation of jujube volatiles during storage.
Wheat gluten prepared by dispersion in the presence of ammonia has unique dough properties similar to those of gliadin. In the present study, the mechanism of expression of these gliadin-like characteristics was investigated. In prolonged stirring with ammonia treatment, gluten gained even less elasticity, as shown by the marked decrease of dough resistance and bandwidth. Size-exclusion HPLC analysis showed that large-molecular sized polymeric glutenins decreased, but small-molecular sized polymeric glutenins increased with increases in ammonia dispersion time. SDS-PAGE of proteins labeled with monobromobimane revealed that the content of free sulfhydryl groups in the D-type of low-molecular weight glutenin subunits (LMW-GS) significantly decreased in ammonia-treated gluten to 56% of that in control gluten. We propose that during ammonia dispersion, free sulfhydryl groups in the D-type of LMW-GS attack the disulfide bonds in large polymeric glutenins and consequently, new small polymeric glutenins are generated by disulfide-sulfhydryl exchange reactions.
Roasted tea is manufactured by roasting green tea at a high temperature and has characteristic flavors (roasted, savory, or sweet) that complement Japanese-style food. Here, we evaluated the sensory quality for six kinds of roasted stem tea products using a sensory test, the rank-rating method, of 52 adolescent panelists. We then elucidated and analyzed the chemical components in these products by gas chromatography-mass spectrometry and principal component analysis. We found that the preferred products were located near the center of the principal component analysis score plot, indicating that the position in the plot was associated with the sensory score of roasted stem tea. We then used these findings to build a predictive model of sensory scores using orthogonal partial least squares regression analysis. This showed that the predicted sensory score was higher when certain pyrazines were present and lower when aldehydes and sugars were present. This is the first study to demonstrate a relationship between the chemical components of roasted stem tea and its sensory score based on the palatability of adolescents for it using metabolomics profiling.
Daqu is an essential starter for the fermentation of Shanxi aged-vinegar. Despite numerous studies on the microbial diversity in Daqu, there is little information on the use of autochthonous yeasts originated from Daqu for vinegar fermentation. Herein, an ester-producing yeast strain, designated Y18 (33.48 g L−1 ester), was isolated from Daqu. The strain Y18 was identified as Candida ethanolica based on sequence analysis of the D1/D2 domain of the 26S rRNA gene, in combination with the morphological and physiological characteristics. The results of gas chromatography-mass spectrometry showed that inoculation of Y18 into the Daqu-based fermentation broth increased the relative abundances of total alcohols and total esters in the Jiulao compared to the non-inoculated control. In particular, the relative abundances of ethanol, isoamyl acetate, and ethyl acetate increased from 31.9% to 38.0%, 1.0% to 1.5%, and 9.8% to 14.5%, respectively. Five different aroma compounds (isoborneol ethanol, isobutanol, benzoic acid methyl ester, acetic acid 2-phenylethyl ester, and hexanoic acid phenyl ester) were detected in the Y18-fortified alcoholic fermentation broth compared to the non-inoculated control. After Y18 fortification, the levels of total acids and total esters in the vinegar increased from 37.42 and 15.30 g L−1 to 40.24 and 19.25 g L−1, respectively. The sensory analysis of Y18-fermented vinegar revealed no abnormal odors but distinct fruity and flowery aromas, with slightly sweet and lingering taste. In conclusion, the inoculation of C. ethanolica strain Y18 into the Daqu-based fermentation broth could markedly enhance the aroma of the Shanxi aged-vinegar by increasing the contents of total acids and total esters, and improve the vinegar quality by conferring the flowery and fruity flavors and slightly sweet, nut-like taste.
The best way to prepare glycated chicken myofibrillar proteins (Mfs) with the strongest antioxidative ability against hydroxyl radicals (•OH), without decreasing solubility in a low ion strength medium, was identified using random-centroid optimization (RCO). Four factors (temperature, relative humidity (RH), reaction time and quantity of ribose) were selected, and 13 vertices were obtained using RCO. Evaluations were carried out relative to each vertex, and the optimal preparatory conditions were sought. Optimal conditions were identified as: temperature, 38°C; RH, 40%; reaction time, 4.55 h; and ribose weight ratio, 10.7. The •OH antioxidant capacity was approximately 5.1 ± 1.3 µmol of gallic acid equivalent/g of protein. Under these conditions, glycated chicken Mfs lost their thermal gel-formation activity.
The aim of this study was to improve the nutritional properties of pasta by adding red grape marc (RGM), which is rich in polyphenols and low in digestible carbohydrates, to increase phenolic antioxidants and decrease the glycemic load/energy intake. Our data showed that the spaghetti enriched with RGM (particle size ≤ 125 µm) and transglutaminase (RGM/TG) was sensory acceptable, had a higher amount of phenolic compounds and antioxidant activity than control spaghetti. Cooking did not affect these nutritional parameters. The bioaccessible fraction from RGM/TG-spaghetti showed a higher amount of polyphenols including anthocyanins, as well as antioxidant activity but a lower amount of glucose in an in vitro digestion model. Thus, enrichment of spaghetti with RGM can increase the beneficial nutritional properties by increasing bioaccessibility of compounds with antioxidant activity and reducing the glycemic load.
Endoplasmic reticulum (ER) stress and the resulting neuronal cell damage have been implicated in the development and progression of Alzheimer's disease. Tunicamycin (TM) induces ER stress in vitro, and the protective effects of the carotenoid zeaxanthin against the effects of TM have recently been studied. Zeaxanthin has been shown to hold several beneficial health properties in human studies. The protective role of zeaxanthin against the toxic effects of TM has recently been studied for the first time. The present study investigated whether zeaxanthin protects SH-SY5Y cells against TM-induced cell damage in vitro. Both pretreatment and post-treatment with zeaxanthin increased cell viability and suppressed lactate dehydrogenase release compared to levels in controls. Further, we found that zeaxanthin considerably ameliorated TM-induced cell damage by protecting the integrity of the mitochondrial membrane decreasing caspase-3 activity, and by reducing the apoptosis rate as well as the expression of the ER stress biomarker GRP78. Modulation of GRP78 may be one of the mechanisms by which zeaxanthin affects cell viability. Our results indicate a potential application of zeaxanthin in the development of new therapeutic drugs for the treatment of Alzheimer's disease.
Based on our recent finding that the “kokumi” taste components, γ-glutamyl-tyrosine, γ-glutamyl-phenylalanine, raffinose, and stachyose, are present in soybean seeds, we aimed to understand whether thermal treatment of soybean seeds can enhance the “kokumi” taste in soymilk or not. Heating was carried out prior to the grinding step in the soymilk production process. The extraction efficiency of the “kokumi” taste components changed with the type of thermal treatment. Autoclave and microwave heating of soybean seeds before grinding caused a high extraction efficiency of “kokumi” taste components compared to unheated and dry heat heating. Traditional methods, such as the thermal treatment at 90°C during grinding, also increased the “kokumi” taste components, but the efficiency and nitrogen yield were low compared to the thermal treatment before grinding. Enhanced extraction of “kokumi” taste components may be originated from the disruption of cell walls of soybean seeds induced by thermal treatment, and the degree of cell damage was closely related with the extraction efficiency of the “kokumi” taste components. Thus, instead of the traditional processes, the thermal treatment before grinding can contribute to the production of soymilk with greater “kokumi” taste components.
When extracting soybean DNA from natto, a traditional Japanese fermented food, Bacillus subtilis var. natto DNA is commonly present despite fastidious washing of samples. We confirmed that DNA extracted from B. subtilis var. natto inhibited PCR amplification of the soybean endogenous lectin gene (Le1) as well as the recombinant nopaline synthase terminator sequence (Nos-ter), which is used to identify genetically modified soybean (GMS) in natto. To mitigate B. subtilis var. natto DNA contamination, we developed a novel method for the specific extraction of Le1 and Nos-ter genes using DNA probes immobilized on streptavidin-coated magnetic beads with hybridization enhancement blockers, which are capable of enhancing the affinity between the target gene DNA and the probe DNA. By using the proposed extraction method, both Le1 and Nos-ter genes could be detected in samples containing B. subtilis var. natto DNA. DNA extraction from commercial nattos and identification of GMS were also successfully accomplished.
Lactobacillus paracasei MCC1849 (LP) has the potential to modulate immune function. To develop a functional LP-fermented dairy beverage, changes in intensities of odorants during two weeks of refrigerated storage were investigated by gas chromatography-olfactometry (GC-O, CharmAnalysis™). A fermented dairy beverage containing 1 × 108 viable LP cells/mL, 0.8% non-fat milk solids, and 0.1% milk fat was prepared, and then stored at 10°C for 0, 1, or 2 weeks before solvent extraction. GC-O of the volatiles in the resulting extracts detected 34 odorants, of which 29 were identified. Among the identified compounds, 4-(4′-hydroxyphenyl)-2-butanone (raspberry ketone) was also detected by GC-mass spectrometry, representing the first identification of this compound as an odorant in fermented dairy products to our knowledge. Principal component analysis of the GC-O data permitted discrimination among the 3 stored samples according to duration of storage, and clarified the major odors contributing to the change in odor characteristics during storage.