Quality Change Of Yellow Broiler Meat Under Chilled Storage And Establishment Of Predictive Model For The Shelf Life

The rich nutrition of yellow broiler meat makes it easy to breed microorganisms,resulting in meat deterioration. As consumers increasingly pay attention to food safety and hygiene, there is a growing enthusiasm for Chilled yellow broiler and its related products.Therefore, the aim of this work is to analyze the quality changes of yellow broiler and build a predictive model for the shelf-life during refrigerated storage.Conclusions are as follows:1. The pH value, moisture content and water activity of Yellow Broiler meat were all decreased first and followed by an increase under-1 ? and 4 ?, respectively. Under storage at-1 ?, the total volatile basic nitrogen(TVB-N) reached at 16.34 mg/100 g on day 6, the sample became second-grade meat, and then it reached at 22.4 mg/100 g on day10, the meat was spoiled. Under storage at 4?, the Yellow Broiler meat changed into second-grade meat(TVB-N 15.94 mg/100g) on day 4 and became spoiled(TVB-N 24.91mg/100g) on day 6. Fat and protein content of Yellow Broiler meat showed a downward trend stored under-1 ? and 4 ?, while thiobarbituric reactive substances(TBARS)showed an upward trend all the time due to oxidation reaction. With regard to the color, the brightness(L*) increased first and then decreased, the redness(a*) decreased all the time,while the yellowness(b*) gradually increased. All above results indicated that Yellow Broiler meat stored under-1 ? kept better quality than under 4?. According to the correlation analysis and factor analysis among the indices, the TVB-N, pH, TBARS, water activity and moisture content were determined as the main indices, while the color, protein content and fat content as reference indices,which could be applied to supervise the quality of chilled Yellow Broiler during storage.2. Sensory index, microorganism(Lactic acid bacteria, Brochothrix thermosphacta,total viable counts, Pseudomonas spp., Enterobacteriaceae) and volatile metabolic compounds were determined. 61 compounds were identified with headspace solid phase microextraction-gas chromatography/mass spectroscopy analysis. In order to simultaneously reflect corruption of chilled yellow chicken under two temperature conditions, the amount of very low or non-detectable substance were removed, and finally received 24 kinds of compounds. Principal component analysis results showed that fresh indicators were 2-butanone, 2-octyl-1-dodecanol, undecane, dodecane, ethyl caproate, ethyl caprylate,anisyl butyrate, 1-nonanal, trichloromethan, while spoilage indicators were acetoin,3-methyl-1-butanol, 3-methy-l-butyraldehyde, 2-ethylhexanol, 2-amino-6-methyl- benzoic acid, 2-pentanone, dimethyl disulfide, ethyl acetate. Partial least squares regression analysis found that 17 compounds mentioned-above could effectively predict the microbial counts of the different microorganisms.3. In order to establish a predictive model for the shelf-life of chilled yellow broiler,samples were packed in trays and stored at-1, 4, 10, 15, and 20 ?, respectively, and their aerobic plate count were determined. Meanwhile, chilled yellow broiler was analyzed for total volatile basic nitrogen during storage at 4 ?. Results showed that the average number of total viable counts was 5.67(lg(CFU/g)) at the end of the shelf-life. The primary models, modified Gompertz, Baranyi and modified Logistic, were applied to describe the change of total bacterial counts with time, and their secondary models, square root equations, were used to describe the change of parameters from primary models with time.The modified Gompertz model was evaluated as the best goodness-of-fit by comparing the model parameters, regression coefficient(R2), bias factor(Bf), accuracy factor(Af) and residual sum of squares(RSS) of the secondary models. On the basis of modified Gompertz, the relative error between predicted value obtained from total bacterial count growth prediction model and its observed shelf life was less than 10%. Which indicated the predictive model was reliable for the shelf-life of chilled yellow broiler meat stored at temperature ranging from-1 to 20 ?.