乳酸菌發酵香腸菌相及理化特性之研究

Abstract

實驗利用本研究室先前自台灣天然發酵火腿及天然發酵香腸中所篩選出較具優勢之乳酸菌Leuconostoc mesenteroides N35、Lactobacillus sakei S3兩菌株做為發酵菌元製作發酵香腸，結合聚合酶連鎖反應-變性梯度膠體電泳（polymerase chain reaction-denaturing gradient gel electrophoresis, PCR-DGGE）及DNA定序等方法鑑定製程各時期乳酸菌及酵母菌之菌相分布，探討菌元添加對發酵香腸製程各時期理化特性的影響，並以掃描式電子顯微鏡（scanning electron microscope, SEM）分析其外觀與菌群分布變化、質地分析儀檢測其感官質地的特性，期能增進產品品質穩定性並達到控制產品製程之目的，進而開發出本土發酵香腸。 結果顯示菌元添加對水分含量、水活性及失重與未添加菌元的自然發酵組並無顯著差異，且添加菌元可快速降低發酵香腸的pH值至4.8，有助於提升食品安全性。利用需培養步驟方法，於各發酵時期共分離出8株乳酸菌（Lb. plantarum、Leu. mesenteroides、Lb. brevis、Lb. coryniformis、Lb. sakei、Lb. mindensis、Comamonas testosteroni及P. stilesii）；而不需培養步驟方法則可另外多分離出Enterococcus faecalis、P. pentosaceus及Bifidobacterium sp.三株乳酸菌。此外，菌相分布的結果顯示，Lb. sakei不管在菌元組或天然發酵組，在終產品裡都是最主要之優勢菌種，因此可推斷Lb. sakei最有潛力作為製作發酵香腸之發酵菌元。透過DGGE技術探討製程各階段之微生物比例，也可作為日後產製條件的參考依據。

Fermented sausage is a fermented meat product resulting from a serial biochemical, microbiological and physical changes during a defined condition of fermentation and ripening process. Fermented sausages in Taiwan are expensive due to lack of related indigenous products and needing to be imported. In our previous study, we isolated two dominant strains, Leuconostoc mesenteroides N35 and Lactobacillas sakei S3, from Taiwan natural fermented ham and sausage, respectively. Thus, in the present study, we inoculated these two strains individually as starter cultures to develop indigenous fermented sausages in Taiwan. We investigated microbial dynamics and physicochemical properties of sausage samples using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) by culture-dependent and culture-independent methods. DNA sequencing technique was performed to confirm the DGGE results. Furthermore, scanning electron microscope (SEM) and texture analyzer were also equipped to analyze the meat structure. Usually, foods with a low pH value (high acidity) develop resistance against microbial spoilage and can last a longer shelf life. Results indicated that cultured group rapidly decreased in pH rate, and then slowly increased at the end of the ripening period because of the protein and lipid decompositions. The degradation of protein and lipid also had effects on the sausage texture. The cultured group samples were much firmer than the controlled ones. The adhesion between fat particles and the meat matrix of the control group was not as tight as the cultured group. Culture-dependent results indicated that 4 dominant LAB species (Leu. mesenteroides, Lb. sakei, Lb. planterum and Pediococcus stilesii) were isolated during the whole manufacturing process. For the culture-independent results, other 3 patterns (Enterococcus faecalis, P. pentosaceus and Bifidobacterium sp.,) were identified by sequencing. In addition, the SEM results demonstrated that the structures of the initial meat matrix were mud-like with small amount of microorganisms, while in the final products, the meat products were wrinkled because of the evaporation and large amount of microorganisms existed on the matrix. In conclusion, our findings suggested that microbial distributions and the physicochemical characteristics of fermented sausage were significantly affected by the addition of starter cultures. Inoculation of Lb. sakei strain in the fermented sausage could shorten the process and improve the quality and stability of the final products. The information will help the design of indigenous starter cultures and develop new meat products in Taiwan.