| Smoked and cooked sausage is a typical type of traditional low-temperature meat products.However,in the storage process,smoked sausages are prone to oxidation and microbial contamination,which could cause quality deterioration and affect the shelf life of sausages.During the processing of meat products,food additives can be used to maintain the quality of meat products and extend the shelf life.With the improvement of economic level and the change of consumer attitude,chemically synthesized preservatives have gradually not been accepted by consumers and the market.Food additives derived from microorganisms have become research hotspots due to their nontoxic and safe characteristics.Propionibacterium fermented extract(PFE)is a mixture of organic acids produced by the fermentation of Propionibacterium acidipropionici,Nisin is produced by the fermentation of Streptococcus lactis and its main components are antibacterial peptides.At present,there is no report on the effect of PFE and Nisin on the quality and shelf life of smoked sausage products.For this thesis,PFE combined with different content of nisin was added to smoked sausage to study the effect of PFEnisin combination on the quality,oxidation degree and microorganisms of smoked sausages,so as to provide a certain theoretical basis for the development and application of natural microbial additives.1.Effect of PFE-Nisin combination on the quality of smoked and cooked sausagesIn this chapter,the main organic acid components in PFE were analyzed by HPLC.Six treatment groups were set as following:adding PFE(0.3%)with 0.01%,0.02%or 0.03%nisin,and adding PFE(0.3%)or nisin(0.03%)alone and adding neither PFE nor nisin as control group.PH value,color(L*,a*,b*values),cooking loss,water content,flavor and sensory quality and textural characteristics of smoked and cooked sausages were analyzed at the 1,4,7 and 10 d of storage.The results showed that the main organic acid components in FEPA were 435.9 mg/g of propionic acid,22.21 mg/g of succinic acid,19.42 mg/g of citric acid,13.29 mg/g of acetic acid and 3.25 mg/g of lactic acid.PFE combined with nisin could significantly reduce the cooking loss of smoked sausages(P<0.05),keep the products’ water content stable during storage,increase the water retention of sausages,and decrease the water holding capacity as the proportion of nisin increased.PFE-nisin combination could significantly increase the L*value and a*value of the smoked sausage during storage(P<0.05),while restraining the increase of its b*value,which is beneficial to maintain the color stability of the sausage during storage.Compared with the treatment group that added Nisin alone,the combining content of 0.01%and 0.02%of Nisin could significantly reduce the hardness of sausages(P<0.05).At the same time,the combined treatment also reduced the chewiness of the product to a certain extent and increased its spring which is beneficial to improve the texture of the smoked sausage during storage.At the same time,the combined treatment also optimized the sensory indicators such as the color and flavor of the sausage.In summary,during the storage of smoked sausages,PFE combined with 0.01%and 0.02%Nisin performs well in terms of quality.2.Effect of PFE-Nisin combination on the oxidation degree of smoked and cooked sausagesIn this chapter,0.3%PFE combined with 0.01%,0.02%,and 0.03%Nisin were added to the smoked sausage,and compared with 0.3%PFE and 0.03%nisin separately to investigate the effect of PFE-Nisin combination on oxidation of the smoked sausages.The thiobarbituric acid value(TBARS)content,the carbonyl value,the sulfhydryl value and the surface hydrophobicity of MP were measured at 1 d,4 d,7 d,and 10 d of chill storage.The results showed that the combined treatment showed better inhibitory effect on lipid oxidation,and the TBARS value of 0.01%and 0.02%of the compound ratio was significantly lower than the separately added treatment group(P<0.05).The combined treatment had a significant inhibitory effect on the protein oxidation of sausages.Compared with the separately added treatment group,the combined treatment could significantly inhibit the increase of carbonyl value and surface hydrophobicity and the decrease of sulfhydryl value(P<0.05).However,its synergy gradually declined with the increase of combined concentration.The experimental results in this chapter showed that the combined treatment could better inhibit the oxidation of lipid and protein during the storage of smoked and cooked sausages,thereby maintaining the quality of the product.3.Effect of PFE-Nisin combination on the microorganism of smoked and cooked sausagesIn this chapter,0.3%PFE combined with 0.01%,0.02%,and 0.03%Nisin were added to the smoked sausage,and compared with 0.3%PFE and 0.03%nisin separately,to determine the effect of PFE-Nisin combination on microorganism of the smoked and cooed sausages.The total viable counts were measured at 1 d,4 d,7 d,and 10 d,and the microbial diversity was investigated at 1 d,14 d,and 28 d of chilled storage.The results showed that PFE combined with nisin could significantly improve its antibacterial ability(P<0.05).Compared with other combined ratios,the ratio of 0.01%showed better synergy and significantly extended the shelf life of smoked sausages.Through high-throughput sequencing analysis,it was found that during the storage period,the microbial diversity of all test groups showed a trend of first decline and then increase.By analyzing the bacterial succession during storage,it was found that compared with the control group and the separately added treatment group,the combined treatment showed a better inhibitory effect on Acinetobacter,Staphylococcus and Sporosarcina.Through heat map analysis,the microbial diversity of 0.01%nisin combined treatment showed significant difference with other treatment groups in the late storage period.The experiments in this chapter showed that the combined treatment could produce obvious antibacterial synergy,and the combined ratio of 0.01%showed a better inhibitory effect on the number and types of microorganisms. |
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