Abstract
BackgroundThe negative sensory properties of casein hydrolysates (HC) often limit their usage in products intended for human consumption, despite HC being nutritious and having many functional benefits. Recent, but taxonomically limited, evidence suggests that other animals also avoid consuming HC when alternatives exist.Methodology/Principal FindingsWe evaluated ingestive responses of five herbivorous species (guinea pig, mountain beaver, gopher, vole, and rabbit) and five omnivorous species (rat, coyote, house mouse, white-footed mouse, and deer mouse; N = 16–18/species) using solid foods containing 20% HC in a series of two-choice preference tests that used a non-protein, cellulose-based alternative. Individuals were also tested with collagen hydrolysate (gelatin; GE) to determine whether it would induce similar ingestive responses to those induced by HC. Despite HC and GE having very different nutritional and sensory qualities, both hydrolysates produced similar preference score patterns. We found that the herbivores generally avoided the hydrolysates while the omnivores consumed them at similar levels to the cellulose diet or, more rarely, preferred them (HC by the white-footed mouse; GE by the rat). Follow-up preference tests pairing HC and the nutritionally equivalent intact casein (C) were performed on the three mouse species and the guinea pigs. For the mice, mean HC preference scores were lower in the HC v C compared to the HC v Cel tests, indicating that HC's sensory qualities negatively affected its consumption. However, responses were species-specific. For the guinea pigs, repeated exposure to HC or C (4.7-h sessions; N = 10) were found to increase subsequent HC preference scores in an HC v C preference test, which was interpreted in the light of conservative foraging strategies thought to typify herbivores.Conclusions/SignificanceThis is the first empirical study of dietary niche-related taxonomic differences in ingestive responses to protein hydrolysates using multiple species under comparable conditions. Our results provide a basis for future work in sensory, physiological, and behavioral mechanisms of hydrolysate avoidance and on the potential use of hydrolysates for pest management.
Highlights
Enzymatic hydrolysis of food proteins results in a mixture of peptides and amino acids that are valued for their increased solubility over intact proteins
A protein in milk, is one of the most commonly hydrolyzed proteins for a variety of reasons: its high nutritional quality, the numerous bioactive peptides that have been identified from casein’s structure that can be released upon hydrolysis [reviewed in 1,2,3], the need for milk-based infant formulas that are hypoallergenic [4], and because humans have a long history with dairy products, such as cheese or fermented drinks, for which hydrolysis is an integral part of the production process [5]
Mountain beavers, gophers and voles consumed less of the hydrolyzed casein (HC) relative to the control, white-footed mice consumed more of the HC relative to the Cel, and the remaining species did not show statistically significant differences between the two alternatives (P.0.0051, Fig. 1)
Summary
Enzymatic hydrolysis of food proteins results in a mixture of peptides and amino acids that are valued for their increased solubility over intact proteins. Hydrolysates generally retain, if not increase, the nutritional and functional properties of the parent proteins. The negative sensory properties of casein hydrolysates [e.g., 6,7,8] often limit their usage, which has stimulated a large body of research focused on identifying the offensive bitter peptides and on methods for improving the flavor [e.g., 9,10,11]. These studies on sensory and nutritive properties of hydrolyzed casein have overwhelmingly been focused on human subjects. The negative sensory properties of casein hydrolysates (HC) often limit their usage in products intended for human consumption, despite HC being nutritious and having many functional benefits. But taxonomically limited, evidence suggests that other animals avoid consuming HC when alternatives exist
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