Effect of heat treatment and solution preparation procedure on colloidal stability of whey protein sour cherry beverage

Heat treatment effect on whey protein-epigallocatechin gallate interaction: A fluorescence spectroscopic analysis

This study aimed to examine the interaction mechanism of polyphenol protein in a heat-treated aqueous solution system using epigallocatechin gallate (EGCG) and whey protein (WP) as raw materials. Further, we hypothesized the binding characteristics of these two compounds. The results were as follows: The quenching mechanism between WP and EGCG was characterized as static quenching. As the temperature increased, the binding constant and the binding force between EGCG and WP both increased. The number of binding sites (denoted as n) between WP and EGCG was approximately 1. Hence, WP provided a single site to bind to EGCG to form a complex. The main binding modes between WP and EGCG were hydrophobic and electrostatic interactions, and they were spontaneously combined into complexes (ΔG < 0). This study provided a basis for the interaction between WP and EGCG under different heating conditions and their combination mode.

Reducing the Flocculation of Milk Tea Using Different Stabilizers to Regulate Tea Proteins

The regulation of flocs derived from polyphenol–protein formation in milk tea has not been fully explored. In this study, the flocculation of milk tea was regulated by adding 10 kinds of stabilizers with different characteristics. The stability coefficient and centrifugal precipitation rate were used as indexes. The optimal concentration ratio of the complex stabilizer was identified using the response surface methodology (RSM), being 0.04% for Arabic gum, 0.02% for β-cyclodextrin and 0.03% for Agar. Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to analyze the characteristics of different stabilizers in milk tea, and our findings were as follows: (1) The relative strength of the peaks in different stable systems was different. The absorption peaks were mainly near the wave numbers 3376 cm−1, 2928 cm−1, 1655 cm−1, 1542 cm−1, 1408 cm−1, 1047 cm−1 and 925 cm−1. (2) The milk tea system was an amorphous structure. The diffraction peak of the composite system was observed to be about 20°. The crystallinity of the milk tea in the compound group was 33.16%, which was higher than that of the blank group (9.67%). (3) The compound stabilizer reduced flocculation, and the stabilizing agents improved the surface order of milk tea. These results indicate that the combination of polysaccharide stabilizers (Arabic gum and agar) and oligosaccharide stabilizers (β-CD) in certain proportions can regulate the flocculation of milk tea and improve its stability. The potential research avenues involving polyphenol–protein complex instability systems and their applications in food development are expanded by this work.

Analysis of Key Chemical Components in Aqueous Extract Sediments of Panax Ginseng at Different Ages

Panax ginseng beverages have been some of the most popular plant drinks among consumers in recent years, but they become turbid and sediment are easily formed during production and marketing, these are some of the key issues that affect the quality of the beverages. In this study, we analysed the physicochemical properties of sediments in aqueous extracts of 3- to 6-year-old ginseng, and by tracing the sediment formation process from 0-40 days, we observed that the sediment was gradually beginning on day 10. The solid content of ginseng aged 5 and 6 years was significantly higher than that of ginseng aged 3 and 4 years. There was no significant difference in the sediment amount sediment in the extracts of ginseng of different ages. The light transmittance of the extracts after centrifugation was significantly higher than before centrifugation. Colour-difference analysis found that there was a significant positive correlation between ginseng age and colour-difference value (ΔE). Chemical composition analysis showed that total sugar and proteins were the main components of the sediment. In addition, ginsenosides, amino acids and minerals were also involved in sediment formation to different degrees. A stepwise regression model was established through principal component analysis (PCA), and the regression equation for predicting the sediment amount was obtained as follows: sediment amount (mg/mL) = 2.906 - 0.126 × C_{Total saponins} - 0.131 × C_{Free amino acids}.

Invited review: Astringency in whey protein beverages

Astringency is the sensation of mouth drying and puckering, and it has also been described as a loss of lubrication in the mouth. Astringency is perceived as an increase in oral friction or roughness. Astringency caused by tannins and other polyphenols has been well documented and studied. Whey proteins are popular for their functional and nutritional quality, but they exhibit astringency, particularly under acidic conditions popular in high acid (pH 3.4) whey protein beverages. Acids cause astringency, but acidic protein beverages have higher astringency than acid alone. Whey proteins are able to interact with salivary proteins, which removes the lubricating saliva layer of the mouth. Whey proteins can also interact directly with epithelial tissue. These various mechanisms of astringency limit whey protein ingredient applications because astringency is undesirable to consumers. A better understanding of the causes of whey protein astringency will improve our ability to produce products that have high consumer liking and deliver excellent nutrition.