石榴汁粉替代发酵基质中蔗糖提升酸奶品质

Pomegranate juice powder improving quality attributes of yogurts by replacing sucrose in fermentation matrix

石榴汁中含有丰富的多酚类物质,是抗氧化剂的良好来源。酸奶是抗氧化剂等生理活性物质的优质载体。为了加快石榴加工产业的发展、丰富酸奶的种类、提升酸奶的品质,该文使用1%、3%、5%石榴汁粉(pomegranate juice powder,PJP)分别等量代替凝固型酸奶发酵基质中的蔗糖,研究了PJP对发酵过程中酸奶基质的pH值、滴定酸度、表观黏度和乳酸菌活力的影响,并分析了对照组与PJP替代组酸奶的拉曼光谱、质构、流变学特性、总酚含量及抗氧化活性的差异。结果表明,PJP的替代没有显著改变发酵终了时基质的pH值、可滴定酸度、表观黏度和拉曼光谱,但缩短了发酵时间,促进了乳酸菌的生长,提高了酸奶的硬度、稠度、黏聚性、黏度指数和总酚含量、FRAP及DPPH·清除率。PJP完全替代蔗糖时,发酵时间从300缩短至280 min,总多酚含量、FRAP和DPPH·清除率分别是对照组的1.84,2.26和1.76倍。酸奶品质的提升可能与PJP中多酚有关,PJP有望替代蔗糖制备更健康的凝固型酸奶。

Pomegranate is rich in polyphenols and is an excellent source of antioxidants, such as polyphenolic substance. However, the concentration of the harvest time, poor shape and inconvenient for eating have limited the sale of pomegranates. Therefore, the processing of pomegranate is beneficial to the appreciation of pomegranate resources. Yogurt a good carrier for bioactive compounds that may offer additional health benefits, is a fermented dairy product suitable for all ages, and the new type yogurts with high qualities and extra functions are more favored by consumers. In order to accelerate the development of pomegranate processing industry, enrich the variety of yogurts and improve the quality of yogurts, in this paper, 1%, 3% and 5% pomegranate juice powder (PJP) whose contents of total carbohydrate, soluble protein and total polyphenols were 0.88 g/g, less than 1.0 mg/g and 0.471 0 mg/g, respectively, was used to replace sucrose in the matrix of set yogurt and the effects of PJP replacement on the parameters in fermentation process, including pH value, titratable acidity, apparent viscosity and lactic acid bacteria vitality were analyze. The Raman spectra, textural properties, rheological properties, total phenolic content and antioxidant activity of the set yogurt with and without PJP replacement were compared. The results indicated that PJP instead of sucrose does not significantly change the pH value, titrable acidity, apparent viscosity and Raman spectrum of the yogurt matrix at the end of fermentation, but the substitution of PJP had a significant (P< 0.05) effect on lactic acid bacteria during fermentation and the properties of yogurt. The replacement of sucrose by PJP defered the solidification time of yogurt, the exponential growth time and the maximum activity time of lactic acid bacteria, but it significantly (P<0.05) increased the maximum activity of lactic acid bacteria in yogurt. It took the control, LD, MD and HD groups 300 minutes, 240 minutes, 260 minutes and 280 minutes, respectively, to reach (4.6±0.1) of pH value, suggesting PJP replacement shortened the fermentation time. The lactic acid bacteria activity of the pomegranate yogurt was 6-7 times that of the control yogurt at the completion of fermentation. What's more, the substitution of PJP could significantly improve the quality of yogurt. The firmness, consistency, cohesiveness and index of viscosity of the control were (65.6±1.9) g,(939.8±61.8) g·s,(14.5±0.8) g and (36.5±9.2) g·s, respectively;while the HD group showed 1.84, 2.26 and 1.76 times that of the control, respectively. PJP-replacement yogurt showed better texture, viscoelasticity and antioxidant activity. Compared with the control, when sucrose was completely replaced by PJP, the total polyphenol content, FRAP and DPPH clearance rate were 1.84 times, 2.26 times and 1.76 times, respectively. Sensory test results showed that PJP substitution of sucrose had a positive effect on the appearance, texture and taste of yogurt, which may be related to the phenolic substance in PJP and the casein interaction in yogurt. PJP can significantly improve the health benefits and quality of yogurt, which is expected to replace sucrose to make healthier yogurt.