益生菌Lactobacillus casei Zhang对凝固型发酵乳质构和挥发性风味物质的影响

摘要

[目的]评价益生菌Lactobacillus casei Zhang(L.casei Zhang)货架期内活菌数的变化及其对发酵乳物理特性和挥发性风味物质的影响.[方法]将2株Streptococcus thermophilus(S.thermophilus)分别与益生菌L.casei Zhang复配发酵,发酵结束(pH 4.5)于4℃冷藏28 d,并对发酵乳各指标进行测定.[结果]4℃贮藏28 d时,发酵乳中益生菌L.casei Zhang活菌数没有显著性变化(P＜0.05),且数量保持在108CFU/g以上；益生菌L.casei Zhang与S.thermophilus复配发酵有利于提高3-羟基-2-丁酮和己酸等挥发性风味物质的含量,同时短期贮藏过程中(1-7 d)可赋予产品较高的黏度、硬度、脆度、胶性和耐嚼性,随着贮藏时间的延长其对产品物理特性的影响随发酵用S.thermophilus菌株的不同而呈现不同的变化.[结论]4℃贮藏28 d过程中,益生菌L.casei Zhang具有非常好的稳定性,同时其与S.thermophillus复配发酵可赋予产品较好的质构和风味.%[Objective] The viability of the probiotic Lactobacillus casei Zhang during the product sbelf-life and its effects on the texture profile and the production of volatile compounds of fermented milk were studied.[Method] L.casei Zhang was inoculated together with either of the two Streptococcus thermophilus strains into pasteurized milk for fermentation,the fermentation was ended when the pH value of fermented milk reached 4.5,then,specific indexes of the products were determined after storage at 4℃C for 28 d.[Result] The viable count ofL.casei Zhang was highly stable (P＜0.05),and was more than 108CFU/g aRer storage at 4℃ for 28 d.Furthermore,by simultaneous inoculating L.casei Zhang and the selected strains ofS.thermophilus into the milk at a certain proportion,it was beneficial to improve the content of 3-hydroxyl-2-butanone and hexylic acid in products; this method also enhanced the viscosity,hardness,fracturability,gumminess and chewiness of the products during short-term storage (1-7 d).In addition,with the extension of storage time,the two S.thermophilus strains used in the fermentation showed different extents of influences on the texture profile of the fermented products.[Conclusion] The products fermented with L.casei Zhang exhibited high viable count after 28 d of refrigerated storage.Meanwhile,the fermented milk would offer a better texture profile and flavor when the strains ofLactobacillus casei Zhang and S.thermophilus were inoculated into the milk simultaneously at a certain proportion.