主成分分析法优选枸杞乳酸菌发酵饮品发酵剂

乳酸菌发酵作为果蔬汁的一种绿色加工技术,不仅可以赋予产品独特的风味,还可以转化其中的活性物质,提高产品的营养价值和保健功效。该研究以湖北杂交枸杞为原料,使用6种乳酸菌(植物乳杆菌、嗜热链球菌、嗜酸乳杆菌、鼠李糖乳杆菌、干酪乳杆菌及发酵乳杆菌)进行发酵,研究发酵前后枸杞果汁理化特性、主要活性成分及体外抗氧化变化,并利用主成分分析进行综合评价优选出理想的发酵菌株。结果表明,6种乳酸菌在枸杞果汁中生长良好,活菌数均能达到10.0 lg CFU/mL以上。发酵后的枸杞果汁中总糖和还原糖含量显著降低(P0.05),且植物乳杆菌和嗜热链球菌产酸能力更强,发酵后总酸含量达6.74、6.07g/kg。与未发酵枸杞果汁相比,经植物乳杆菌、嗜热链球菌、鼠李糖乳杆菌和发酵乳杆菌发酵的枸杞果汁中总酚含量增加了13.76%～28.07%,而嗜酸乳杆菌和干酪乳杆菌发酵后无显著性差异(P0.05)。6种乳酸菌发酵后枸杞果汁中总黄酮含量增加了55.80%～161.97%。发酵枸杞果汁的抗氧化活性与发酵前相比均有显著提高(P0.05)。基于主成分分析的综合评价函数显示经植物乳杆菌、发酵乳杆菌发酵的枸杞果汁品质更优,适宜作为开发枸杞高值化绿色加工饮品的发酵剂。

Optimizing lactic acid bacteria starter culture for wolfberry juice fermentation using principal component analysis

Wolfberry (Lyciumbarbarum) is a typical traditional Chinese medicinal and edible fruit, sharing a variety of ingredients and functional activities, such as anti-aging, immune regulation, and anti-atherosclerosis. One of the wolfberry cultivars, Hubei hybrid wolfberry was introduced from the doubled Ningxia wolfberry that crossed with the local wild one in Enshi Prefecture, Jianshi County of Hubei Province in China. A previous study found that this new type of wolfberry was not suitable to process into the conventional dried products, due mainly to higher moisture content, compared with the original Ningxia wolfberry. Therefore, it is highly urgent to develop a new processing approach for the wolfberry products, further improving the conversion rate of Hubei hybrid wolfberry. Alternatively, a characteristic fruit fermentation using lactic acid bacteria can provide a unique flavor product, while transform the types and increase the content of active substances for high nutritional value and health benefits. However, only a few reports were focused on the effects of lactic acid bacteria fermentation on the nutritional quality of wolfberry juice. Taking Hubei hybrid wolfberry as raw material, this study aims to investigate the physicochemical properties, main active components, and antioxidant activity in vitro of wolfberry juice before and after lactic acid bacteria fermentation. 6 kinds of lactic acid bacteria were selected (Lactobacillus plantarum, Streptococcus thermophilus, Lactobacillus acidophilus, Lactobacillus rhamnosus, Lactobacillus casei, and Lactobacillus fermentum) for fermentation. A principal component analysis was utilized to evaluate the quality of fermented wolfberry juice, where the most suitable lactic acid bacteria strain was obtained for wolfberry juice fermentation. The results showed that 6 kinds of lactic acid bacteria grew well in wolfberry juice, where the viable count reached above 10.0 lg CFU/mL. The total contents of sugar and reducing sugar in the juice were significantly reduced (P <0.05) after fermentation. A high capacity of acid production was achieved in the Lactobacillus plantarum and Streptococcus thermophilus, where the total acid contents were 6.74 and 6.07 g/kg, respectively. The total phenol content in wolfberry juice fermented by Lactobacillus plantarum, Streptococcus thermophilus, Lactobacillus rhamnosus, and Lactobacillus fermentum increased by 13.76% to 28.07%, compared with unfermented wolfberry juice. Nevertheless, there was no significant difference in the content of total phenols in the wolfberry juice fermented by Lactobacillus acidophilus and Lactobacillus casei (P>0.05). The total flavonoid content increased by 55.80% to 161.97% after fermentation. The antioxidant activities of fermented wolfberry juice were also significantly improved (P<0.05). Correlation analysis showed that the increase in antioxidant activity was closely related to the content of total phenols and total flavonoids. Three principal components were extracted in a principal component analysis, covering three levels of fermentability, nutritional quality, and functionality, indicating a higher quality of fermented wolfberry juice. The cumulative variance contribution rate was 82.344%. The comprehensive score ranking demonstrated that the quality of wolfberry juice fermented by Lactobacillus plantarum and Lactobacillus fermentum was better, suitable for a starter for green processed beverages of Hubei hybrid wolfberry.