Effect of protein type on the loss of flavor compounds in protein bars

Abstract

A problem with high-protein foods is that flavor compounds added are “lost” and no longer perceptible by the consumers over time, due to the flavor compounds undergoing various binding interactions with the protein. Knowing which flavors interact more extensively with which proteins can help manufacturers decide if a certain flavor should be added in excess in order for the flavor to still be perceptible by the time consumers consume it. Gaining an understanding of which proteins work as a better carrier for which flavor compounds allows for better formulations that holds up well over time without degradation in sensory quality. The aim of the project was to investigate the effects of using different types of protein isolate (whey, soy, rice and pea) on the rate of loss of nine different flavors compounds (allyl sulfide, isoamyl acetate, furfuryl mercaptan, benzaldehyde, methyl salicylate, menthol, D-carvone, γ- nonalactone and trans-α-ionone) in a protein bar matrix system. The nine flavor compounds were added a protein bar model system and stored at 45°C over four weeks for an accelerated shelf-life study. Samples were taken at 0, 1, 2 and 4 week s of storage time. Flavor compounds were extracted from each sample by Stir Bar Sorptive Extraction and thermally desorbed in the injection port of a gas chromatography. The amount of detectable flavor compounds (assumed to not be bound to the protein) was determined semiquantitatively using the peak areas of each flavor compound on the chromatogram and corrected with an internal standard. The percentage loss of each flavor compound was then calculated at each time point, with Week 0 as a baseline of 100%. Soy protein showed the least binding with flavor compounds initially, especially with compounds of lower molecular weight. However, soy protein had a very high rate of reactions with flavor compounds over one month of storage. Rice protein the slowest rate of binding interactions with flavor compounds, and was the most unreactive with low molecular weights flavor compounds such as allyl sulfide, isoamyl acetate and benzaldehyde. Pea and whey protein were both rather reactive with flavor compounds, but pea protein showed better performance with flavor compounds of higher molecular weights. Unlike whey and soy protein, rice and pea protein are not as commonly used in food products due to their lack of functionality. However, as a flavor carrier, rice protein shows much potential due to its lack of interaction with flavor compounds. In addition, the emerging trend of plant proteins might increase consumer demand and make these proteins more cost-effective to produce too.