Peptide Size Distribution of Hydrolysates – In general, for each enzyme tested, incubation of each raw material with the higher concentration of enzyme and for a longer duration resulted in a ‘beneficial’ shift in the peptide size profile of the hydrolysates (i.e. an increase in the proportion of smaller peptides). This is highlighted in Figure 2, which shows results for each raw material using the ‘best’ enzyme at ‘non-optimal’ concentration and duration compared to ‘optimal’ concentration and duration. With optimised conditions, we found that 100% of peptides were ≤3 kDa, and more than 75% were < 0.5 kDa (Figure 2).
Based on the collective evidence of several studies in a number of species (e.g. rat, pig, dog, human; see (Zhangi & Matthews, 2010) for an overview, it is generally well accepted that:
- Absorption of peptides is better compared to intact protein.
- Absorption of peptides is better than free amino acids.
- Absorption of small peptides is better than of large peptides.
Physiologically, the majority of amino acids are absorbed as small peptides consisting of 2 or 3 amino acids joined together (di- and tri-peptides, respectively). Therefore it would be expected that ingestion of a protein hydrolysate containing high proportions of di- and tri-peptides would facilitate protein digestion and absorption, resulting in increased digestibility and amino acid bioavailability. The average molecular weight of an amino acid is 110 Daltons (Da), so di- and tri-peptides would have a molecular weight of approximately 220-330 Da (0.2-0.3 kDa). Our results in achieving protein hydrolysates with more than 75% of peptides smaller than 0.5 kDa (i.e. up to ~ 5 amino acids) means the protein in our kibbles would be highly digestible and easily absorbed by the pets eating it. It is planned to demonstrate this through a feeding study in collaboration with the Faculty of Veterinary Medicine, University of Ghent.
In addition, achieving 100% of peptides of 3 kDa or smaller decreases the risk of triggering an allergic reaction to the protein sources and can therefore be considered hypoallergenic.