Avoidance of hydrolyzed casein by mice

Abstract

When casein, a milk protein, is hydrolyzed, it renders human foods that contain it (e.g., hypoallergenic infant formula, cheeses) distasteful to many people. This rejection of hydrolyzed casein (HC)-containing foods has recently been found to also occur in a non-human species (deer, Odocoileus spp.). Identifying other animals that avoid HC would facilitate understanding how and why HC-containing food is often rejected. This study determined whether HC-containing food is avoided by Mus musculus and whether consumption patterns were sensitive to testing conditions, specifically food form (powder, pellet or dough) and food access (ad libitum or 1.5 h/day following 6 h of food deprivation). Diets were offered in two-choice tests that paired an HC-containing food with an intact casein-containing alternative at seven protein concentrations (0%-50% w/w). Five experimental groups were tested under different combinations of food form and food access. Three groups (ad lib/powder, ad lib/pellet, and 1.5 h/pellet) avoided the HC diet starting at the 30% protein level. At the 40% and 50% protein levels, all groups showed strong avoidance of HC. Although testing conditions influenced total caloric intake and body weight gain, avoidance of HC at the highest concentrations was robust to the manipulations in experimental conditions. Our study suggests that mice may be a useful model for understanding the mechanisms of HC rejection.

The Macronutrients, Appetite, and Energy Intake

“…Some AAs (e.g., Gly, D-His, -Phe, -Trp, -Tyr, and L-Ala, -Leu) (237), peptides (aspartame) and proteins (monellin and thaumatin) (228) are sweet, but these are not strongly preferred. In addition, mice (91) and humans (204) avoid or negatively rate hydrolyzed casein in a dose-dependent manner. Even umami-tasting L-glutamate is not preferred over sucrose when in the form of monosodium glutamate (258).…”

Casein-derived bioactive peptides: Biological effects, industrial uses, safety aspects and regulatory status

“…Casein hydrolysates may also be used to protect plants against animals (Field, Kimball, Mennella, Beauchamp, & Bachmanov, 2008). For instance, casein hydrolysates were shown to be as effective as a commercial deer repellent in preventing white-tailed deer plant damage (Kimball, Nolte, & Perry, 2005).…”

Bitter peptides and bitter taste receptors

“…The avoidance of protein hydrolysates by these animals is not nutritionally driven, but is actually the result of a factor within the protein that these animals find unpalatable [43]. In fact, animals should choose hydrolyzed casein-containing foods over casein-containing foods when nutritionally compromised, due to its shorter gastrointestinal transit time and increased rate of amino acid adsorption compared to intact casein [44]. Bitterness also develops from soy protein products, which is of great concern because of the worldwide demand for edible plant protein sources and because soybean protein and soybean-derived peptides can play an important role in physiology, particularly the prevention of chronic diseases (reviewed in [45]).…”