Study On Spoilage Of Thawed Pork And Optimization Of Thawing Methods

Separation and identification of harmful bacteria and its regrowth in thawed porkwere studied in this research. Then the specific spoilage organisms were inoculated intothawed pork at different storage temperatures (4℃,0℃and－5℃, respectivley).Sensory evaluation score, chromatic value, aerobic bacteria count, drip loss, totalvolatile basic nitrogen (TVB-N) value and thio-barbituric acid (TBA) value weredetected, respectively, at each storage day. The aim of above research was to explore themechanism of spoilage on thawed pork. Meanwhile, in order to keep the high quality ofthawed pork, methods of thawing, such as air thawing, microwave thawing andultrasonic thawing, were selected and compared in this paper. The result indicated thatmicrowave thawing was a better one among these methods. And then furtheroptimization was applied for the microwave thawing, which could be practice referencefor meat industry. The results were showed as follows:Firstly, it indicated that Pseudomonas spp., Brochothrix thermosphacta,Enterbacteriaceae and lactobacillus were initial harmful bacteria of thawed porkthrough analysis of harmful bacteria of thawed pork. Pseudomonas spp., B.thermosphacta, Enterbacteriaceae were dominating ones among the initial harmfulbacteria. From the analysis of total plate count and the regrowth of harmful bacteria, itshowed that Pseudomonas spp. and B. thermosphacta grew faster than others, withmore colony forming units (CFU) observed. Enterbacteriaceae grew fast at4℃storage.Furthermore, the amount of lactobacillus was the least and grew slowest among thedetected bacteria. As a conclusion, appropriate measure would be adopted to control thegrowing of microorganism in thawed pork in meat industry.Secondly, different parameters of thawed pork, which inoculated by specificspoilage organism during storage, were detected, including sensory evaluation,chromatic value, drip loss, pH value, amount of colony, TVB-N and TBA. The resultsindicated that the scores of thawed pork which inoculated by Pseudomonas spp. and B.thermosphacta were lower than by Enterbacteriaceae and control; the specific spoilageorganism grew observably during the storage at4℃and0℃, and Pseudomonas spp. and B. thermosphacta grew faster, especially B. thermosphacta with highest amount atthe end of storage; The results of TVB-N value showed that the samples whichinoculated by Pseudomonas spp. and Enterbacteriaceae increased fast, and the valuewas exceed20mg/100g at4℃storage, while the samples by Pseudomonas spp. and B.thermosphacta was approximately14mg/100g also with higher increase tendency. TheY value which to combine TVBN and total plate count, was selected as the index ofspoilage ability in this paper. The results indicated that the Y value of sample withPseudomonas spp. was the higher one than other treatments. Furthermore, the spoilageability of samples by Pseudomonas spp. and B. thermosphacta was found to be themore significant ones compared with other groups, and Enterbacteriaceae treatment bethe fast t at4℃storage.Thirdly, effect of different thawing methods on the quality of frozen pork wasstudied, and pork after slaughtered for48h was selected in the further study of thawingoptimization. The results indicated that microwave thawing was better than air thawingand ultrasonic thawing in keeping the quality of thawed pork; the optimization oftemperature covered20℃,25℃,30℃and intermittent technology. It showed that thethawed pork quality might be improved by keeping microwave thawing10minutes andintermittent10minutes at25℃, and the total bacterial count, color, tenderness, TVB-N,etc. were improved than before.In conclusion, this paper indicated that Pseudomonas spp. and B. thermosphactawere dominating ones among the initial harmful bacteria and their spoilage ability wassignificant. Moreover, results of comparsion and optimization of thawing methodsshowed that intermittent microwave thawing was better than other methods in keepingthe quality of thawed pork. This study might be a supplement for basic theory ofmicroorganism and significance for meat industry.