Application of Lipase Based Enzymatic Time Temperature Indicator (TTI) as Quality Marker for Frozen Chicken Meat

Abstract

Lipase based enzymatic TTI was prepared using tricaprylin as substrate to monitor thermal abuse history of frozen chicken meat during supply chain. TTI showed an irreversible distinct colour change from initial green to intermediate orange to final red during temperature abuse with corresponding decrease in pH of TTI solution from 8.11 to 6.93 and 5.75, respectively. Temperature dynamicity of TTI on kinetic parameters was derived through Arrhenius equation and activation energy (Ea) of TTI was calculated as 50.94 kJ/mol. At different temperature abuse conditions viz. 5 ± 1 °C, 15 ± 1 °C, 25 ± 1 °C, and 35 ± 1 °C, quantitative changes in various parameters of chicken meat were evaluated and correlated with distinct colour response of TTI. The results showed significant correlation of parameters with colour changes in TTI at 35 ± 1 °C, insignificant correlation at 5 ± 1 °C and 15 ± 1 °C and slight correlation at 25 ± 1 °C indicating concurrent change in quality characteristics of frozen chicken meat on exposure to different temperature abuse conditions. Therefore, suggesting single lipase based enzymatic TTI cannot be utilized for quality marking of frozen chicken meat at different temperature abuse conditions.

Introduction

Chicken meat is in demand due to nutritional adequacy, universal availability and freedom from religious taboos. The high protein nutrient rich lean chicken meat makes concordant with modern health conscious consumer's diet profile. On other aspect, quality and safety aspect of meat and meat products are precarious issues as it affects the consumer's health directly or indirectly. Packaging plays a fundamental role in shielding overall quality of meat and meat products from the point of fabrication to point of consumption. During transit, temperature of storage in supply chain and accidental high temperature exposure time are crucial factors affecting quality and safety of perishable food products (Anbukarasu et al., 2017; Raab et al., 2008).To restrict growth of microorganisms and enhance safety during supply chain, it is mandatory to maintain cold chain until product reaches consumer's door step (Likar and Jevšnik, 2006). Maximum cold chain breakdown occurs during processing, transportation and storage and results in temperature abuse affecting intrinsic components of perishable products thereby deterioration of quality. Therefore, a TTI (a type of intelligent packaging) based system would be required for effective monitoring of entire production to distribution cycle and to provide information on remaining shelf-life of food products (Taoukis and Labuza, 2003).

Enzymatic TTI works on the principle of enzyme-substrate reaction which depends on temperature and concentration of enzymes; causing colour changes in TTI at specific time interval due to production of various acidic/basic metabolites. Thus, enzymatic TTI has advantage of being applied for different food products undergoing quality changes during temperature abuse as concentration of enzyme and temperature are important factors for TTI colour changes. In comparison to different types of TTIs known i.e., diffusion-based, microbial, polymer-based, photochemical and electronic, enzymatic TTI costs less and can be applied easily on the surface of package (Meng et al., 2018). Various enzymatic TTIs using lipase, esterase, β-glucosidase, amylase or laccase have been developed for various categories of food (Kim et al., 2012). Among these enzymatic TTIs, particularly lipase based TTI shows an irreversible colour change induced by pH decline resulting from controlled enzymatic hydrolysis of lipid substrate (Taoukis, 2001; Kerry et al., 2006). Using above principle, lipase based TTI was selected to monitor changes in quality of frozen chicken meat exposed to different thermal abuse conditions during supply chain.

Materials and Methods

Materials    Chemicals and media used in present study were commercially procured from Sigma-Aldrich (U.S.A.) and HiMedia^®, Mumbai, India.

Source of Meat    The slaughtered dressed poultry birds (Gallus domesticus) of similar age group reared under same feeding and management conditions were procured from ICAR-Central Avian Research Institute, Izatnagar. They were manually deboned in experimental abattoir of Livestock Products Technology Division, ICAR-Indian Veterinary Research Institute and visible fat and connective tissue was removed to obtain lean meat. The meat was packed in low density polyethylene bags (100 gauge) and kept at −18 ± 2 °C till its further use.

Preparation of lipase based enzymatic TTI    The lipase based enzymatic TTI was prepared according to the protocol given by Kim et al. (2012) after slight modification. TTI reaction solution (Solution A) consists of tricaprylin, Triton X-100 and pH indicator solution (mixture of bromothymol blue, methyl red and neutral red). TTI reaction solution was mixed in a homogenizer (Ultra Turrax IKA, Model T18 Basic) for 6 min at 9 000 rpm. Solution B consists of phosphate-citrate buffer (Na₂HPO₄ and citric acid, pH 7.5) with 4% agarose powder which was heated up to 60 °C to dissolve agarose gel and then cooled up to 35 °C. Finally, solution A and solution B were thoroughly mixed in equal amount with addition of 10 units of lipase enzyme per 500 mL of TTI reaction solution. TTI reaction solution was poured into glass petridish to prepare thin gel based sheet by putting in freezer for 30 min. TTI sheet was cut into 2 × 2 cm² size strip and packed into 2.5 × 2.5 cm² low density polyethylene (LDPE) film sachet, which was properly sealed and stored at −18 ± 2 °C for further use.

Dynamicity of lipase based enzymatic TTI    L*, a*, b* chroma system, which uses corresponding value of total colour difference (TCD)/chromacity value (ΔE) as dynamic parameters, were used to analyse the dynamic change in TTI colour. ΔE was expressed by following equation:   

Where, ΔL* is brightness difference between initiation and each time interval, Δa* is redness-greenness difference between initiation and each time interval, and Δb* is yellowness-blueness difference between initiation and each time interval (Francis, 1983).

Lipase based enzymatic TTI were tested isothermally for distinct intermediate and final colour change at different temperatures with help of MiniScan EZ Hunter Lab (4500 L Spectrophotometer, Hunter Associate Laboratory, Inc., Reston). To measure chromacity value (ΔE), instrument was used with a large area view i.e. 45° circumferential illumination and 0° observation angle. The temperature dynamicity of TTI on kinetic parameters was derived through Arrhenius equation and activation energy (Ea) was calculated according to theory given by Taoukis and Labuza (1989).

Sample preparation    For dynamic temperature abuse study, 150 g of chicken meat was packed in LDPE bags (100 gauge) and fabricated TTI was attached to it on the surface and stored in deep freezer at −18 ± 2 °C for 24h before exposing to temperature abuse conditions. The conditions were simulated in laboratory by using incubator and refrigerator. The temperature of the core of the meat was monitored by using probe thermometer (Digi-thermo, WT-2, China) and meat samples were exposed to temperature abuse conditions of 5 ± 1 °C, 15 ± 1 °C, 25 ± 1 °C, and 35 ± 1 °C till final colour of lipase based enzymatic TTI appears.

Determination of meat quality parameters with colour changes in lipase based enzymatic TTI    Various physico-chemical parameters like pH (Trout et al., 1992), extract release volume (Strange et al., 1977), free amino acids (Rosen, 1957), total volatile basic nitrogen (Pearson, 1968) and microbiological counts i.e., aerobic plate count (APC), psychrophillic count and yeast and mold count (APHA, 2001) and instrumental colour analysis using Lovibond Tintometer (Froehlich et al., 1983) were estimated with concurrent change in the colour of TTI at temperature abuse conditions.

Sensory evaluation    Trained sensory panelists consisting of scientists and post graduate students of the Livestock Products Technology Division, ICAR-Indian Veterinary Research Institute participated in the sensory evaluation. The panelists were briefed about the nature of the experiments without disclosing the identity of the samples. About 10 g meat sample were subjected to sensory evaluation on the basis of colour, general appearance and acceptability using five point hedonic scales where, 1= Undesirable, 2= Slightly desirable, 3= Moderately desirable, 4= Desirable, 5= Very much desirable scores were used in sensory evaluation. The scores of sensory evaluation were analysed using non-parametric multiple range tests (Kruskal-Wallis and Steel-Dwass method).

Statistical Analysis    Each experiment was repeated three times and the data generated for different meat quality parameters were compiled and analysed using one way analysis of variance with SPSS (Version 20.0 for Windows; SPSS, Chicago. 111., U.S.A.) according to the procedure of Snedecor and Cochran (1995) and means were compared by using Tukey's honestly significant difference (HSD) test.

Results and Discussion

Colour alteration pattern of lipase based enzymatic TTI    The lipase based enzymatic TTI was exposed at 5 ± 1 °C, 15 ± 1 °C, 25 ± 1 °C, and 35 ± 1 °C for observing initial to intermediate and final colour changes. The changes in colour (ΔE) and pH of TTI reaction solution were measured. Fig. 1 shows a graph between pH and ΔE of TTI depicting pH of TTI decreased significantly from 8.11 ± 0.02 to 5.75 ± 0.05, whereas ΔE value increased simultaneously from 0 to 38.08 ± 0.05 during initial to final colour change of TTI at 35 ± 1 °C. Likewise, at 5 ± 1 °C, 15 ± 1 °C, and 25 ± 1 °C, similar pH decrease and ΔE value increase were noted for lipase based enzymatic TTI. The distinct colour change in lipase based enzymatic TTI from its initial green to intermediate orange to final red colour is shown in Fig. 2. This distinct colour change occurs due to the action of lipase on substrate tricaprylin; which causes release of free fatty acids thereby reducing the pH of medium and subsequent colour change. The distinct colour change to the red in lipase based TTI was obtained only when the ΔE response reached a value of 25 or more (Kim et al., 2012).

Fig. 1.

Changes in pH and ΔE value of lipase based enzymatic TTI at 35 ± 1 °C. (■=Depicts changes in ΔE value; ◆=Depicts changes in pH value)

Fig. 2.

Colour change pattern in lipase based enzymatic TTI.

Dynamicity of lipase based enzymatic TTI    The time taken to reach intermediate and final colour change of TTI at 5 ± 1 °C, 15 ± 1 °C, 25 ± 1 °C, and 35 ± 1 °C is shown in Fig. 3. A gradual reduction in time taken for final colour development was observed with increasing temperature; because the activity of lipase enzyme was temperature dependent, thereby the release of free fatty acids and colour development were also approaches towards temperature dependency. The time taken for final colour response (ΔE=38.08 ± 0.05) was 52 h, 24 h, 12 h and 6 h at 5 ± 1 °C, 15 ± 1 °C, 25 ± 1 °C, and 35 ± 1 °C, respectively. By applying linear regression curve analysis, the response rate (k) was 0.73 (R²=0.99), 1.58 (R²=0.97), 3.18 (R²=0.99) and 6.35 (R²=0.99) at 5 ± 1 °C, 15 ± 1 °C, 25 ± 1 °C, and at 35 ± 1 °C, respectively with significant coefficient of determinations (R² ≥0.96) indicating that the proposed functions represented the data collected from different temperature with strong accuracy. The activation energy (Ea) of lipase based enzymatic TTI was calculated by plotting a curve between 1/T and lnk (Fig. 4) and was obtained as 50.94 kJ/mol (R²=0.99) which is low in comparison to commercially available TTIs having activation energy (Ea) values ranging from 68.70 kJ/mol (VITSAB Type M) to 92.67 kJ/mol (Fresh Check Indicator TJ2) (Mendoza et al., 2004), because to qualify as reliable TTI, the difference between activation energy (Ea) of TTI and monitored food should be less than 20 kJ/mol (Taoukis et al., 1999).

Fig. 3.

Time taken to reach intermediate and final colour change of lipase based enzymatic TTI at 5 ± 1 °C, 15 ± 1 °C, 25 ± 1 °C and 35 ± 1 °C.

Fig. 4.

Arrhenius plot for lipase based enzymatic TTI for determination of activation energy.

Simulation of meat quality parameter with change in TTI colour during temperature abuse Physico-chemical parameters    The pH value of frozen chicken meat depended on storage temperature conditions (5 ± 1 °C, 15 ± 1 °C, 25 ± 1 °C, and 35 ± 1 °C). In this study, the pH of meat ranges from 5.52 to 5.92 during temperature abuse trials, but there was no large difference between pH values was observed (Table 1). A decreased pH with increased duration of temperature abuse might be due to production of metabolites i.e., lactic acid, peptides and free amino acids inside cell as a result of glycolytic and enzymatic reactions. Similar decrease in the pH of chicken meat during refrigerated stored chicken meat experiment was also reported by Vaithiyanathan et al. (2008) and Kumar et al. (2012). Chicken meat generally has a normal ultimate pH of 5.7–6.0. Any alteration beyond this range suggests that either temperature of storage was not maintained properly or any spoilage/contamination has been initiated. The decrease in pH was more at 25 ± 1 °C and 35 ± 1 °C than 5 ± 1 °C and 15 ± 1 °C due to higher temperature exposure creating conditions for rapid enzymatic actions on meat components leading to production of metabolites i.e., lactic acid, peptides and free amino acids. The low temperature abuse did not greatly affect pH values of meat as reported by Jeong et al. (2006).

Table 1. Changes in meat quality parameters with TTI colour response at different temperatures.

Parameters		Physicochemical parameters			Microbiological characteristics (in log10 CFU/g)			Sensory attributes			Instrumental colour analysis
	pH	ERV (mL)	FAA (mg/100 g)	TVBN (mg/100 g)	APC	Psychrophilic count	Yeast and mold count	Colour	General appearance	Acceptability	a value	b value
Initial Colour at −18±2°C (Control)	5.92±0.02a1A1a2A2	30.10±0.55a1A1a2A2	43.68±1.01c1C1c2C2	7.70±0.03c1C1c2C2	3.49±0.04c1C1c2C2	2.29±0.04b1C1c2C2	ND	3.86±0.09a1A1a2A2	3.71±0.14a1A1a2A2	3.77±0.11a1A1a2A2	2.90±0.10a1A1a2A2	2.98±0.18a1B1c2B2
Intermediate Colour at 5±1°C	5.75±0.02a1b1	25.01±0.70b1	102.57±3.58b1	11.66±0.59b1	4.49±0.04b1	2.75±0.04a1	2.01±0.02b1	3.29±0.22b1	3.10±0.20a1	3.06±0.22a1	2.33±0.06b1	3.11±0.10a1
Final Colour at 5±1°C	5.56±0.08c1	23.86±0.66b1	113.58±2.93a1	17.73±0.46a1	5.60±0.07a1	2.87±0.05a1	2.20±0.03a1	2.71±0.14c1	3.00±0.17a1	2.84±0.12a1	2.18±0.07b1	3.23±0.14a1
Intermediate Colour at 15±1°C	5.62±0.04B1	23.36±0.82B1	91.36±1.18B1	9.33±0.46B1	4.14±0.01B1	3.51±0.01B1	2.10±0.03B1	3.00±0.01B1	3.30±0.15A1	3.30±0.31A1	2.46±0.03B1	3.46±0.06A1
Final Colour at 15±1°C	5.53±0.02B1	21.10±0.64B1	115.38±0.36A1	12.60±0.51A1	4.22±0.01A1	3.77±0.02A1	2.20±0.02A1	2.53±0.18C1	2.84±0.54A1	2.89±0.52A1	2.23±0.04B1	3.66±0.02A1
Intermediate Colour at 25±1°C	5.65±0.06b2	24.86±0.36b2	92.29±0.91b2	13.30±0.59b2	4.22±.03b2	3.71±.03b2	1.94±0.02b2	2.60±0.07b2	2.69±0.12a2	2.89±0.07b2	1.78±0.03b2	3.40±0.03b2
Final Colour at 25±1°C	5.52±0.10b2	19.58±0.73c2	124.08±0.83a2	19.13±0.30a2	5.19±.02a2	4.11±.02a2	2.23±0.01a2	2.29±0.15c2	2.36±0.05b2	2.39±0.05c2	1.26±0.02c2	3.85±0.02a2
Intermediate Colour at 35±1°C	5.77±0.03B2	26.16±0.23B2	104.06±0.69B2	12.60±0.51B2	5.77±0.06B2	4.09±0.01B2	2.29±0.03B2	3.07±0.07B2	3.36±0.07A2	3.02±0.03B2	2.28±0.03B2	3.11±0.02B2
Final Colour at 35±1°C	5.54±0.05C2	20.93±0.73C2	144.08±0.52A2	20.76±1.04A2	6.31±0.02A2	5.23±0.01A2	2.80±0.02A2	2.20±0.09C2	2.22±0.09B2	2.36±0.07C2	1.53±0.02C2	3.81±0.03A2

• Mean ± S.E. with different superscripts in row vary significantly (P<0.05) with respect to Control (−18 ± 2 °C) at different temperatures. a1, b1, c1 for 5 ± 1 °C treatment; A1, B1, C1 for 15 ± 1 °C treatment; a2, b2, c2 for 25 ± 1 °C treatment; and A2, B2, C2 for 35 ± 1 °C treatments.

• (ERV=Extract Release Volume, FAA=Free Amino Acid, TVBN=Total Volatile Basic Nitrogen, APC= Aerobic Plate Count, a value=Redness, b value=Yellowness)

• For physicochemical parameters, microbiological characteristics and instrumental colour analysis, means were compared by using Tukey's honestly significant difference (HSD) test (P<0.05).

• For 5 point hedonic sensory evaluation, 1= Undesirable, 2= Slightly desirable, 3= Moderately desirable, 4= Desirable, 5= Very much desirable analysed using non-parametric multiple range test (Kruskal-Wallis and Steel-Dwass method, P<0.05).

Extract Release Value (ERV) had a significant potential for determining the quality of meat during storage. During temperature abuse conditions (5 ± 1 °C, 15 ± 1 °C, 25 ± 1 °C, and 35 ± 1 °C), a decline in ERV values was observed from 30.10 mL to 19.58 mL (Table 1) which might be attributed to hydrolysis of meat protein caused by enzymatic and bacterial actions during incipient spoilage of chicken meat (Jay, 1964). The increase in hydration capacity of meat proteins occurs due to amino sugar complexes produced by the spoilage biota resulting in decrease of ERV (Shelef and Jay, 1969). At 25 ± 1 °C and 35 ± 1 °C, the value of ERV has been lower than the prescribed meat safety limit (<20 mL) recommended by Food Safety and Standards Authority of India (FSSAI, 2016) and suggesting meat is unsafe for consumption and product preparation due to incipient microbial spoilage. At 5 ± 1 °C and 15 ± 1 °C, the ERV values are within the prescribed meat safety limit (>20 mL) thereby recommending meat is safe for consumption and value addition. A decrease in the ERV of chicken meat was observed by Talukder et al. (2017), Vaithiyanathan et al. (2008), and Kumar et al. (2012) in refrigerated stored chicken meat experimental research.

Free amino acid (group of 13 amino acids reported by Niewiarowicz et al., 1978) content of chicken meat is a major determinant of quality and safety during storage and supply chain. The breakdown of meat proteins by the catalytic action of active endogenous enzymes present in meat food system causes release of FAA. A significant (P<0.05) increase in FAA content of meat sample from 43.68 to 144.08 mg/100 g was investigated with intermediate and final colour alterations of TTI during temperature abuse conditions (5 ± 1 °C, 15 ± 1 °C, 25 ± 1 °C, and 35 ± 1 °C) (Table 1). At 25 ± 1 °C and 35 ± 1 °C, increase in FAA was more than prescribed meat safety index (>120 mg/100 g) at final colour alteration of TTI that clearly indicates microbial spoilage in meat suggesting unfit and unwholesome for human consumption. However, at 5 ± 1 °C and 15 ± 1 °C, FAA values was found within the meat safety limits (<120 mg/100 g) recommending fit for consumption and product preparation usage. Niewiarowicz et al. (1978) reported similar observation of increased free amino acids ranging from 70 to 130 mg/100 g during refrigerated storage of chicken for six days. Likewise, Soni et al. (2018) elucidated the increased free amino acids content in chicken meat from 61.53 to 126.93 during storage study of refrigerated chicken for seven days.

The release of total volatile basic nitrogen (TVBN) is also depended on temperature abuse conditions (5 ± 1 °C, 15 ± 1 °C, 25 ± 1 °C and 35 ± 1 °C). A significant increase in TVBN value of chicken meat sample was observed with concurrent alterations in intermediate and final colour of TTI (Table 1). The increased TVBN value might be attributed to catalytic action of endogenous enzymes and growth of microbes causing deamination of amino acids leading to production of ammonia and other basic volatile compounds. At 25 ± 1 °C and 35 ± 1 °C, TVBN content was investigated more than normal meat safety index (20 mg/100 g) during final stages of colour alterations of TTI indicating microbial spoilage and quality deterioration in meat thereby causing unfit for consumption. Soni et al. (2018), Talukder et al. (2017), and Zhang et al. (2012) also reported significant increased TVBN values for chicken meat stored under refrigeration but values did not exceed 20 mg/100 g, which is indicative limit for deterioration (Rosen, 1957).

Microbiological Parameters    Microbiological observations were also made during intermediate and final colour alterations of TTI at different temperature abuse conditions (5 ± 1 °C, 15 ± 1 °C, 25 ± 1 °C, and 35 ± 1 °C) in terms of aerobic plate count (APC), psychrophilic count and yeast and mold count. The initial load of micro-organisms is important with regards to meat quality and safety aspects with particular emphasis on behaviour of spoilage microflora. Although, initial microbial load is quite less, a significant (P<0.05) increase in APC, psychrophilic count and yeast and mold count of chicken meat samples were recorded during exposure to different temperature abuse conditions with concurrent development of intermediate and final colour of TTI (Table 1). At 35 ± 1 °C, the APC of frozen poultry meat was 6.31 log₁₀ CFU/g and distinct off-odour was noticed thereby indicating incipient spoilage conditions. As depicted in table 1, gradual increase in microbial count at 5 ± 1 °C, 15 ± 1 °C, and 25 ± 1 °C was recorded but counts were within the prescribed meat safety limits suggested by FSSAI (2017) recommending safe for consumption. An increasing trend in APC of aerobically packaged poultry meat from 4.60–6.38 log₁₀ CFU/g during storage at 4 °C for 4 d was reported by Zhang et al. (2012). Although, temperature of 5 ± 1 °C does not allow growth of majority of the microbes, some psychrophiles can grow and cause spoilage which cannot be easily detected by change in colour of TTI. Huang et al. (2011) also reported increase in total psychrophilic count of boneless and skinless broiler chicken meat at 4 °C from 4.27 log₁₀ CFU/g on 0 d to 6.29 log₁₀ CFU/g on 9^th day. Likewise, Soni et al. (2018) and Talukder et al. (2017) also reported increase in APC and psychrophilic count during refrigeration storage study of chicken while correlating with colour changes in TTIs and quality indicators.

Sensory attributes    Sensory scores of meat and meat products are major factors which affect the like and dislike to a great extent and affects the marketing appeal of consumers. Sensory qualities scores changes significantly with passage of time during thermal abuse conditions (5 ± 1 °C, 15 ± 1 °C, 25 ± 1 °C, and 35 ± 1 °C) with concurrent change in colour of TTI were determined by Kruskal-Wallis and Steel-Dwass tests (Table 1). The significant decrease (P<0.05) in colour score were observed during thermal abuse conditions due to conversion of oxymyoglobin to metmyoglobin, which causes discolouration of meat. The significant decrease (P<0.05) in general appearance score were observed at final colour change score at 25 ± 1 °C and 35 ± 1 °C. The significant decrease (P<0.05) in overall acceptability score were observed at intermediate and final colour change score at 25 ± 1 °C and 35 ± 1 °C. Talukder et al. (2017) reported similar sensory evaluation score for chicken meat stored at refrigeration temperature on 5-point and 8-point descriptive hedonic scale.

Colour of meat is most significant parameter determining consumer appeal, freshness and acceptability. At 25 ± 1 °C and 35 ± 1 °C, redness (a value) value of chicken meat samples decreased significantly (P<0.05) and yellowness (b value) increased significantly (P<0.05) (Table 1). This trend might be due to high temperature abuse causing loss of myoglobin in meat extract and meat became dull due to decreased colour intensity as myoglobin is not available for oxymyoglobin formation. However, there was no remarkable change in a value and b value of chicken meat kept at 5 ± 1 °C and 15 ± 1 °C. As refrigerated storage period increased, metmyoglobin accumulation in meat tissue increased consistently causing decreased redness and increased yellowness (Sahoo and Anjaneyulu, 1997). The decreased a value and increased b value during storage were also reported by Soni et al. (2018) and Talukder et al. (2017) whereas Saucier et al. (2000) observed a significant increase in b value in stored poultry meat.

Conclusion

From results and discussion, it was noticed that physico-chemical i.e., ERV (>20 mL), FAA (>120 mg/100 g), TVBN (>20 mg/100 g), microbiological i.e., APC (> 6 log10 CFU/g), sensorial attributes (score between slightly desirable and moderately desirable) and instrumental colour analysis values of frozen chicken meat attached with lipase based enzymatic TTI was significantly correlated with final colour change of TTI at 35 ± 1 °C, because meat quality parameters values measured were more than the prescribed meat safety limit. Therefore, lipase based enzymatic TTI able to monitor the quality of frozen chicken meat during thermal abuse conditions of 35 ± 1 °C. However, the meat quality parameters values at 5 ± 1 °C, 15 ± 1 °C and 25 ± 1 °C had shown insignificant correlation with the final colour change of TTI as physico-chemical, microbiological and sensorial parameters values are within the prescribed meat safety limit. So, lipase based enzymatic TTI cannot monitor the quality of frozen chicken meat during thermal abuse conditions of 5 ± 1 °C, 15 ± 1 °C and 25 ± 1 °C. In other words, single type of lipase based enzymatic TTI cannot be used for monitoring of quality at different thermal abuse conditions. Therefore, it is suggested that TTIs develops in future for monitoring temperature abuse conditions for different categories of food should be such that single TTI can work at all temperature conditions.

Acknowledgements    The work was supported by the Ministry of Food Processing Industries, Government of India (SERB/MOFPI/0019/2014).

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