为优化乳酸菌发酵低糖桑葚复合果酱工艺条件,并分析发酵对其风味物质的影响,在单因素试验基础上,分别采用正交试验法和均匀试验法对乳酸菌发酵和果酱浓缩条件进行优化,采用离子色谱法测定果酱有机酸的组成与含量,顶空固相微萃取-气相色谱-串联质谱法分析果酱风味物质成分.结果表明,果酱最佳发酵条件为:乳酸菌接种量1×105CFU/ml,蔗糖添加量8.00%,脱脂乳粉添加量5.00%,37℃发酵20 h.最佳浓缩条件为:初始pH值3.8,蔗糖添加量28.90%,增稠剂(低甲氧基果胶 : 黄原胶=1.0 : 1.0)添加量0.50%,氯化钙添加量0.04%.所得果酱呈明亮的紫红色,稳定性和口感良好,有桑葚果香和发酵特有的气味和芳香.与未发酵果酱相比,乳酸菌发酵提高了果酱中乳酸含量、乙酸含量和柠檬酸含量,发酵果酱产生的挥发性物质比未发酵果酱多8种,包括5种酯类,2种烯类和1种脂肪酸.乳酸菌发酵可显著增加桑葚复合果酱中的有机酸和香气成分,可以用来加工风味独特的新型乳酸菌发酵低糖桑葚复合果酱.%In order to optimize processing conditions of low-sugar complex mulberry jam fermented by lactic acid bacteria and analyze the volatile flavor components in fermentation jam,orthogonal and uniform experiments based on sin-gle-factor test were employed to optimize fermentation and jam concentration conditions,respectively. Organic acids in jam were determined by ion chromatography with conducting detection. Volatile flavor components were analyzed by headspace solid-phase micro-extraction and gas chromatography-mass spectrometry. Results showed that the optimum fermentation con-dition was:1×105CFU/ml inoculation of lactic acid bacteria,added with 8.00% sucrose,5.00% dried skim milk,fermen-tation time 20 h. The optimum concentration condition was: pulp pH 3.8, added with 28.90% sucrose, 0.50% complex thickeners (low-methoxyl pectin:xanthan gum=1.0 : 1.0) and 0.04% CaCl2?2H2O. The final product, purple-red in color,had delicate taste,good stability and the flavor both of mulberry fruit and yoghourt. The content of lactic acid,acetic acid and citric acid were increased after fermentation. The total of eight volatile flavor compounds were newly produced by lactic acid bacteria in fermented jam, inclu-ding five esters, two kinds of alkene and one leinoleic acid. Lactic acid bacteria fermentation can be applied for the production of novel low-sugar complex mulberry jam with unique enjoyable flavor.
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