Comparing astringency and sourness of whey protein beverages acidified with four different acids

Abstract

Increasing interest in whey protein beverages stems from the wide range of nutritional benefits whey proteins have to offer. A useful characteristic of whey proteins is their solubility over a wide pH range, however in order to ensure clarity of a ready-to-drink whey protein beverage, it needs to be manufactured at a pH of approximately 3.4. At an acidic pH of 3.4, the beverages become astringent and can lead to consumer acceptability issues. The main objective of this research was to determine which, if any, of four different acids (hydrochloric, malic, phosphoric, tartaric) achieved the lowest perceived astringency rating when used to acidify a 4% (w/v) whey protein isolate (WPI) solution to pH 3.4. A secondary objective was to identify the buffer capacities of each acid in both a water solution and WPI solution, in efforts to detect a relationship between buffer capacity and perceived astringency. Sourness ratings for each sample were also gathered. A 4% (w/v) WPI solution acidified with hydrochloric acid generated the lowest perceived astringency and sourness ratings. Conversely, the malic acid WPI sample produced the highest perceived astringency rating. Additionally, hydrochloric and phosphoric acid samples buffered the least within the pH range of interest (3.4-7.0). This research indicates a potential relationship between the perceived astringency of an acidified-WPI solution and the buffer capacity of the acidulant used.