Evaluation of the alpha-amylase activity as an indicator of pasteurization efficiency and microbiological quality of liquid whole eggs

Abstract

In order to evaluate the efficiency of the pasteurization process in liquid whole eggs, an UV/visible spectrophotometric method was developed and validated for the assessment of alpha-amylase activity. Samples were collected from 30 lots of raw eggs (n = 30) and divided into three groups: one was reserved for analysis of the raw eggs, the second group was pasteurized at 61.1°C for 3.5 minutes (n = 30), and the third group was pasteurized at 64.4°C for 2.5 minutes (n = 30). In addition to assessing alpha-amylase activity, the microbiological quality of the samples was also evaluated by counting total and thermotolerant coliforms, mesophilic aerobic microorganisms, Staphylococcus spp., and Salmonella spp. The validated spectrophotometric method demonstrated linearity, with a coefficient of determination (R2) greater than 0.99, limits of detection (LOD) and quantification (LOQ) of 0.48 mg kg-1 and 1.16 mg kg-1, respectively, and acceptable precision and accuracy with relative standard deviation (RSD) values of less than 10% and recovery rates between 98.81% and 105.40%. The results for alpha-amylase activity in the raw egg samples showed high enzyme activity due to near-complete hydrolysis of the starch, while in the eggs pasteurized at 61.1°C, partial inactivation of the enzyme was observed. In the samples of whole eggs pasteurized at 64.4°C, starch hydrolysis did not occur due to enzyme inactivation. The results of the microbiological analyses showed a decrease (P < 0.0001) in the counts for all the studied microorganisms and in the frequency of Salmonella spp. in the pasteurized egg samples according to the two binomials under investigation, compared to the raw egg samples, which showed high rates of contamination (P < 0.0001). After pasteurization, only one sample (3.33%) was positive for Salmonella spp., indicating failure in the pasteurization process, which was confirmed by the alpha-amylase test. It was concluded that the validated methodology for testing alpha-amylase activity is adequate for assessing the efficiency of the pasteurization process, and that the time-temperature binomial used in this study is suitable to produce pasteurized eggs with high microbiological quality.

Study of Proximate Composition, Quality Characteristics and Microbial Quality of Microwave Treated Liquid Whole Egg (LWE) Samples

“…Whereas, further decrease in α-amylase activity of microwave treated samples was found with increasing time levels due to action of heat. The results obtained in present investigation are similar with the findings of Silva et al, (2017) during evaluation of alpha-amylase activity as an indicator of pasteurization efficiency.…”

“…A blue violet colour indicates that egg has been adequately pasteurized. The final starch concentration in the samples of pasteurized whole liquid egg was obtained by absorbance readings using UV-Visible spectrophotometer as described by Silva et al, 2017. Hunter's lab colourimeter was used for the measurement of colour changes in egg liquid during studies.…”

Critical review on conventional spectroscopic α‐amylase activity detection methods: merits, demerits, and future prospects

“…The presence of even a small amount of α ‐amylase can hydrolyse the starch and result in significant viscosity loss and eventually degrade the quality of the final product . In egg processing, α ‐amylase activity is measured to ensure the efficiency of the pasteurization process . Thus, for quality control purposes, it is necessary to measure residual α ‐amylase activity in these food materials to ensure the quality of the final product.…”

Risk Management of Egg and Egg Products: Advanced Methods Applied

“…Thus, UV-C treatment is a promising technology to prolong the shelf life of liquid egg products [85,86]. The time-temperature binomial is crucial to produce pasteurized eggs with high microbiological quality [87].…”