【作者】 张丽；

【导师】 任迪峰；

【作者基本信息】 北京林业大学 ， 农业硕士（专业学位）， 2020， 硕士

【摘要】 龙葵果在我国多省均有分布,具有较高的营养价值和丰富的活性成分。龙葵果实质地柔软多汁,鲜果不易储存,更适合制成果汁。本文研究了龙葵果汁的高压微射流均质和混菌发酵工艺,为龙葵果深加工提供了新途径,提高龙葵果的经济效益。本研究对植物乳杆菌B7和果酒酿酒酵母SY的混合发酵工艺进行了优化;探究了不同高压微射流均质条件对龙葵果汁物理性质和发酵液活性成分的影响,确定了最适的高压微射流均质条件;探究了不同处理后果汁的基本成分、活性成分以及色度的变化,分析了样品体外抗氧化、体外抗过敏以及体外降血糖的活性。主要研究结果如下:龙葵果中粗水分为88.90±0.12%,粗蛋白质为1.46±0.09%,总酸为1.53±0.11%,总糖为12.15±0.72%,还原糖为8.72±0.14%,维生素C为26.03±0.53 mg/100g,总花色苷为0.82±0.08 mg/g,总多酚为1.10±0.20 mg/g,总黄酮为0.44±0.05 mg/g,澳洲茄碱为33.19±0.07μg/g。植物乳杆菌B7的最佳接种时间为16 h。将植物乳杆菌B7和果酒酿酒酵母SY同时接入发酵基质中,龙葵果发酵液的总多酚含量可达到较高水平。根据响应面实验获得最佳的混菌发酵工艺参数为:植物乳杆菌B7接种量为3.50%,酵母菌接种量为0.20%,发酵温度为40℃,发酵时间为25 h,在最优条件下,发酵液中总多酚含量实际值为3.06±0.02 mg/m L。随着高压微射流均质压力和次数的增加,小颗粒物质所占比例增加;在100 MPa下处理4次,样品的平均粒径最小,达2.47±0.06μm;离心沉淀率在100 MPa下处理4次时达到最低,为0.40±0.11%;不稳定性系数呈现下降趋势。经过100 MPa的高压微射流均质处理4次后,龙葵果汁的Zeta电位绝对值变化不大;龙葵果汁的黏度不再随剪切速率的增加而变化,剪切应力减小,触变性降低;观察到微观结构由完整、大块的形态变成破碎、细小的形态。高压微射流处理使龙葵果汁及发酵液的总多酚和总黄酮含量显著提高。最适的高压微射流均质条件为在100 MPa下处理4次。与原果汁相比,龙葵果发酵液中总多酚和总黄酮含量显著提高,总酸含量显著提高,总糖、还原糖和可溶性固形物含量显著降低,可溶性蛋白含量变化较小。经过高压微射流和混菌发酵后,龙葵果发酵液的亮度降低,a*值和b*值提高,色泽偏黄。龙葵果发酵液的透明质酸酶抑制率与原果汁相比显著提高,为58.46%;对羟基自由基、ABTS~+自由基、DPPH·自由基的清除率显著提高,分别达66.96%、85.13%、93.41%;对α-淀粉酶的抑制率和α-葡萄糖苷酶的抑制率显著提高,达到47.75%和28.46%。总多酚的含量与龙葵果发酵液的生物活性具有极强相关性,是发酵液中主要的活性成分。本研究为龙葵果的深加工提供了一定的理论基础,提高了其经济价值,拓宽了高压微射流技术的应用范围。更多还原

【Abstract】 Solanum nigrum L.is wildly distributed in many provinces in China.It has high nutritional value and rich active ingredients.The berries are soft and juicy and fresh berries are not easy to store,so they are more suitable for making juice.In this research,the high-pressure microfluidization and mixed fermentation processes of Solanum nigrum L.berries were studied.This study provided a new way for further processing of Solanum nigrum L.berries and increased their economic benefits.In this study,the mixed fermentation processes of Lactobacillus plantarum B7 and Saccharomyces cerevisiae SY were optimized.The effects of different high-pressure microfluidization conditions on the physical properties of Solanum nigrum L.berries juice and the active components of fermentation broth were studied,and the most suitable high-pressure microfluidization conditions were determined.The changes of basic ingredients,active ingredients and color of the fermented liquid were explored,meanwhile the anti-oxidation,anti-allergy and anti-hyperglycemic activities in vitro were analyzed.The results showed that:The crude water content of the Solanum nigrum L.berries was 88.90±0.12%,the crude protein content was 1.46±0.09%,the total acid content was 1.53±0.11%,the total sugar content was12.15±0.72%,the reducing sugar content was 8.72±0.14%,and the content of vitamin C was26.03±0.53 mg/100g,the total anthocyanin content was 0.82±0.08 mg/g,the total polyphenol content was 1.10±0.20 mg/g,the total flavonoid content was 0.44±0.05 mg/g,and the solanine content was 33.19±0.07μg/g.The optimal fermentation time for Lactobacillus plantarum B7 was 16 h.By combining Lactobacillus plantarum B7 and Saccharomyces cerevisiae SY into the fermentation substrate at the same time,the total polyphenol content of the fermented liquid can reach a relatively high level.According to the response surface test,the best process conditions for mixed fermentation were:the inoculation amount of Lactobacillus plantarum was 3.50%,the inoculation amount of yeast was 0.20%,the fermentation temperature was 40℃,and the fermentation time was 25 h.Under the optimal conditions,the actual value of the total polyphenol content in the fermentation broth was3.06±0.02 mg/m L.With the increase of the pressure and the number of high-pressure microfluidization,the proportion of small particles increased;the average particle size of the sample was the smallest when it was treated 4 times at 100 MPa,reaching 2.47±0.06μm.The centrifugal sedimentation rate reached the lowest when treated 4 times under 100 MPa,which was 0.4±0.11%.The instability coefficient showed a downward trend.After 4 times of high-pressure microfluidization at 100 MPa,the absolute value of the Zeta potential changed little,and the viscosity of Solanum nigrum L.berries juice no longer changed with the increase of shear rate,meanwhile the shear stress and the thixotropy decreased.Observed that the microstructure changed from a complete,bulky appearance to a broken,tiny appearance.The high-pressure microfluidization significantly increased the total polyphenols and total flavonoids content of Solanum nigrum L.berries juice and fermentation broth.The most suitable high-pressure microfluidization conditions were 4 treatments and 100 MPa.Compared with the original juice,the content of total polyphenols and total flavonoids in Solanum nigrum L.berries fermentation broth increased significantly,the total acid content increased,the contents of total sugar and reducing sugar and soluble solids decreased significantly,and the content of soluble protein changed little.After the processes of high-pressure microfluidization and mixed fermentation,the brightness of the Solanum nigrum L.berries fermentation broth decreased,and the color was yellowish.The a*value and the b*value increased.After the processes of high pressure microfluidization and mixed fermentation,the inhibitory rate of hyaluronidase in the fermentation broth was significantly increased to 58.46%.The scavenging rates for hydroxyl radicals,ABTS~+radicals,and DPPH·radicals were significantly improved,reaching 66.96%,85.13%,and 93.41%,respectively.The inhibition rate ofα-amylase andα-glucosidase were significantly increased,reaching 47.75%and 28.46%.The content of total polyphenols had a strong correlation with the biological activity of the fermented liquid,and total polyphenols are the main active ingredients.This study provided a theoretical basis for the further processing of Solanum nigrum L.berries,and improved their economic value,furthermore,broadened the application range of high-pressure microfluidization technology.更多还原