Duan J, Park S-I, Daeschel M A, Zhao Y
Dept. of Food Science and Technology, 100 Wiegand Hall, Oregon State Univ., Corvallis, OR 97331-6602, USA.
J Food Sci. 2007 Nov;72(9):M355-62. doi: 10.1111/j.1750-3841.2007.00556.x.
This study investigated the antimicrobial activities of chitosan-lysozyme (CL) composite films and coatings against tested microorganisms inoculated onto the surface of Mozzarella cheese. CL film-forming solutions (FFS) with a pH of 4.4 to 4.5 were prepared by incorporating 0% or 60% lysozyme (per dry weight of chitosan) into chitosan FFS with or without a pH adjustment to 5.2. Sliced cheese was subjected to 3 CL package applications: film, lamination on a multilayer coextruded film, and coating. Cheese was inoculated with Listeria monocytogenes, Escherichia coli, or Pseudomonas fluorescens at 10(4) CFU/g, or with mold and yeast at 10(2) CFU/g. Inoculated cheese was individually vacuum packaged and stored at 10 degrees C for sampling at 1, 7, and 14 d for bacteria, and at 10, 20, and 30 d for fungi. Inoculated bacteria survived but failed to multiply in untreated cheese during storage. Treated cheese received 0.43- to 1.25-, 0.40- to 1.40-, and 0.32- to 1.35-log reductions in E. coli, P. fluorescens, and L. monocytogenes, respectively. Incorporation of 60% lysozyme in chitosan FFS showed greater antimicrobial effect than chitosan alone on P. fluorescens and L. monocytogenes. The pH adjustment only affected the antimicrobial activity on L. monocytogenes, with lower pH (unadjusted) showing greater antimicrobial effect than pH 5.2. Mold and yeast increased to 10(5) CFU/g in untreated cheese after 30 d storage. Growth of mold was completely inhibited in cheese packaged with CL films, while 0.24- to 1.90- and 0.06- to 0.50-log reductions in mold populations were observed in cheese packaged with CL-laminated films and coatings, respectively. All CL packaging applications resulted in 0.01- to 0.64-log reduction in yeast populations.
本研究调查了壳聚糖 - 溶菌酶（CL）复合膜和涂层对接种在马苏里拉奶酪表面的受试微生物的抗菌活性。通过将0%或60%的溶菌酶（相对于壳聚糖干重）加入壳聚糖成膜溶液（FFS）中，制备pH为4.4至4.5的CL成膜溶液，成膜溶液有或没有将pH值调节至5.2。将切片奶酪进行3种CL包装处理：薄膜包装、层压在多层共挤薄膜上以及涂层处理。奶酪接种单核细胞增生李斯特菌、大肠杆菌或荧光假单胞菌，接种量为10⁴CFU/g，或接种霉菌和酵母菌，接种量为10²CFU/g。接种后的奶酪分别进行真空包装，并在10℃下储存，在第1、7和14天对细菌进行取样，在第10、20和30天对真菌进行取样。接种的细菌在未处理的奶酪储存期间存活但未繁殖。经过处理的奶酪中，大肠杆菌、荧光假单胞菌和单核细胞增生李斯特菌分别减少了0.43至1.25、0.40至1.40和0.32至1.35个对数级。在壳聚糖FFS中加入60%的溶菌酶对荧光假单胞菌和单核细胞增生李斯特菌的抗菌效果比单独使用壳聚糖更好。pH调节仅影响对单核细胞增生李斯特菌的抗菌活性，较低的pH值（未调节）显示出比pH 5.2更大的抗菌效果。未处理的奶酪在储存30天后，霉菌和酵母菌数量增加到10⁵CFU/g。用CL薄膜包装的奶酪中霉菌生长完全受到抑制，而用CL层压薄膜和涂层包装的奶酪中霉菌数量分别减少了0.24至1.90和0.06至0.50个对数级。所有CL包装处理均使酵母菌数量减少了0.01至0.64个对数级。
