Purpose

The purpose of this paper is to evaluate the effect of green tea polyphenols addition on physicochemical, microbiological and bioactive characteristics of yogurt.

Design/methodology/approach

Two incorporation methods of polyphenols were evaluated: direct addition or incorporated within protein particles of whey protein concentrate and gelatin. During yogurt’s shelf life, structure characteristics (water holding capacity, textural and rheological parameters), lactic acid bacteria (LAB) viability and polyphenols antioxidant activity were analyzed. Also, polyphenol bioaccesibility after in vitro digestion was evaluated.

Findings

Polyphenols addition (by the two methods used) did not affect the dynamics of the fermentation process, nor the LAB viability during storage. The color parameter a* for the yogurts with the highest polyphenol concentrations showed positive values (tending to red), but not visible to the naked eye. Because of the ability of polyphenols to interact with milk proteins, yogurts with polyphenols presented higher values in firmness and cohesiveness with respect to the control. Additionally, the incorporation of polyphenols in protein particles increased even more these parameters because of the higher protein content of these formulations. After simulated digestion, a high polyphenol bioaccesibility was observed, and the antioxidant activity was retained, which could be explained by the “protector” effect of the milk matrix.

Practical implications

Yogurt supplementation with green tea polyphenols is feasible for the development of functional food. However, the use of protein particles would not provide an extra benefit because milk proteins already act as protective molecules of polyphenols.

Originality/value

This study shows not only the physico-chemical implications of including polyphenols in yogurt but also their bioaccesibility after an in vitro digestion, revealing a suitable manner for delivery of antioxidants in a dairy product like yogurt.

中文翻译：

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添加绿茶多酚对酸奶理化，微生物和生物活性特性的影响

目的

本文的目的是评估添加绿茶多酚对酸奶的理化，微生物和生物活性特性的影响。

设计/方法/方法

评价了多酚的两种掺入方法：直接添加或掺入乳清蛋白浓缩物和明胶的蛋白颗粒中。在酸奶的货架期中，分析了结构特征（持水量，质地和流变参数），乳酸菌（LAB）的活力和多酚的抗氧化活性。此外，评估了体外消化后的多酚生物可吸收性。

发现

多酚的添加（通过所使用的两种方法）不影响发酵过程的动力学，也不影响存储过程中LAB的活力。颜色参数a*对于多酚浓度最高的酸奶显示正值（趋于红色），但肉眼看不到。由于多酚与牛奶蛋白相互作用的能力，与对照相比，具有多酚的酸奶在硬度和内聚性方面表现出更高的价值。另外，由于这些制剂中较高的蛋白质含量，蛋白质颗粒中多酚的掺入甚至增加了这些参数。经过模拟消化后，观察到了较高的多酚生物相容性，并保留了抗氧化活性，这可以用牛奶基质的“保护作用”来解释。

实际影响

酸奶中添加绿茶多酚可用于开发功能性食品。但是，使用蛋白质颗粒不会带来额外的好处，因为牛奶蛋白质已经充当了多酚的保护分子。

创意/价值

这项研究不仅显示了在酸奶中包含多酚的物理化学意义，而且还显示了其在体外消化后的生物适应性，从而揭示了在乳制品（如酸奶）中输送抗氧化剂的合适方式。