Shelf life of shrimp coated with gelatin
Description
This study aimed to assess the shelf life of Pacific white shrimp coated with gelatin extracted from Nile tilapia concerning microbial degradation, pH levels, total volatile bases nitrogen (TVB-N), trimethylamine nitrogen (TMA-N), and thiobarbituric acid-reactive substances (TBARS) assessed at intervals of 30 days (T0, T30, T60, T90, T120, T150 and T180 days).
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1 Microbiological analysis Psychrotrophic bacteria counts (PBC) were determined following the recommendations of the American Public Health Association (APHA 2015), preparing decimal dilutions of shrimp homogenized in 0.85% NaCl (Dinâmica, Brazil) saline and inoculation on PCA agar plate medium (Merck, Germany) using the pour plate method and incubating the plates at 7 °C for 8 days in a DBO incubation oven (model Q315M, Quimis, Brazil). After the incubation period, the number of Colony Forming Units (CFU) was determined. To calculate the Standard Plate Count (SPC), plates with growth between 25 and 250 CFU were selected and calculated by multiplying the number of CFU by the inverse of the dilution factor. 2 Physicochemical analysis The pH of shrimp samples C and GC treatments was measured by a bench pH meter (Kasvi, Brazil), homogenizing 5.0 g of the macerated sample with 50 mL of distilled water (APHA 2015), in nine repetitions. Total volatile base nitrogen (TVB-N) and trimethylamine nitrogen (TMA-N) were measured by the steam distillation method, as described by (Malle and Tao 1987). Lipid oxidation was performed through the evaluation of thiobarbituric acid-reactive substances (TBARS), according to Vyncke (1970). To find the TBARS value in mg of malondialdehyde equivalent per kilogram of fish (mg MDA eq./Kg muscle), the standard curve was used from 1,1,3,3-tetraethoxypropane (TEP), from equation (Eq. (1)): SRATB = (Absorbance – 0,032) / 0.0789 Eq. (1) 3 Statistical analysis Analyzes of shelf life physicochemical parameters were performed using Jamovi(R) software, version 2.4.6. Initially, the Shapiro-Wilk test was applied to test the normality of the values obtained, while the Levene’s test was used to verify the homogeneity of the data. Then, the values were submitted to Student's t-test to check for a significant difference (p < 0.05) between the treatments.