Microbial Succession During Ripening And Influence Of Starter Culture On The Quality Of Fermented Dry Sausages

Microbial succession and physico-chemical changes during ripening of two Chinese-style fermented dry sausages, together with the influence of starter culture on the quality of fermented dry sausages, are investigated. The main results and conclusions are as follows:1. Lactic acid bacteria (LAB) are the predominant microflora during ripening of fermented sausages. They rapidly maximized with population of 1.58×109cfu/g and 3.29×108cfu/g at day 3 and day 7 in the two type products respectively, and stayed almost constant afterwards. From day 28, they decreased. Micrococci-staphylococci, second to lactic acid bacteria in count, increased too during fermentation or in the first week. However, their increment is small in contrast to that of LAB. Micrococci-staphylococci, with the maximum of about 107cfu/g, were far below LAB all the time in the process of fermented dry sausages. Enterobacteriaceae are spoilage bacteria and undesirable in fermented sausages. Generally, the initial counts of Enterobacteriaceae decreased during the whole process of maturation. In type B sausage, the decrease of Enterobacteriaceae was more evident and they disappeared in the end product, whereas in type A sausage, Enterobacteriaceae were still detectable after ripening.2. The initial values of pH are different between the two type products for the difference in formulation. However, their change patterns are similar during ripening. In the first three days of fermentation, the pH dropped rapidly to below 5.3 and minimized on day 14. Afterwards, a slight increase in pH was observed which might have been due to amines and ammonia production. The final pH value of the two type fermented dry sausage are 4.89 and 4.88 respectively. There was almost no change in moisture content during fermentation. And the dehydration rate increased by day 4. However, after day 14, it degreased slowly. The final moisture contents are the same in the two different products, between 29.40% and 29.50%, regardless higher initial value in type B fermented dry sausage. Their final total nitrogen and total fat contents are 3.55% and 4.82%, 40.14% and 32.77%, respectively.3. The use of starter culture accelerated fermentation and an earlier fall in pH to below 5.3 was observed in treatments inoculated with lactic acid bacteria (Lpentosus). In the batches inoculate with lactic acid bacteria (Lpentosus), a higher dehydration rate and lower final moisture content were also determined, indicating the effect of the rate and extent of pH drop on the water loss. In the batches inoculated with L. pentosus, less viable Enterobacteriacea in contrast to controls at different stages were also found, reflecting L. pentosus has an inhibitory effect on Enterobacteriacea and accelerated their death. In the meantime, L. pentosus also inhibited the growth of Micrococci-staphylococci which was negative to the sensory quality of fermented dry sausages according to sensory analysis. According to the numbers of yeast determined in different batches, it indicated that the combination addition of Lpentosus 31-1 and 5. xulosus might have a significant inhibitory effect on yeasts. Starter culture has no influence on the content of total nitrogen and fat in terms of dry material.4. The development of firm texture of fermented dry sausages is attributed to lactic acidfermentation. Lactic acid bacteria (L. pentosus) enhanced the value of hardness, chewiness and gumminess of sausages. Staphylococci have chromogenic effect and enhanced the value of redness (a*) of fermented dry sausage. The addition of starter culture significantly enhanced the total acceptability of fermented dry sausages judged by our sensory panelist.5. Proteolysis and lipolysis can be mainly attributed to tissue enzymes though microbial metabolism activities significantly increased free amino acids (FAA) and free fatty acids (FFA) in samples determined during ripening (p