PULSED LIGHT TREATMENT AS A STRATEGY TO MODULATE CASEIN PROTEOLYSIS DURING SIMULATED DIGESTION IN OLDER ADULTS’ CONDITIONS

Caseins, the major milk proteins, are commonly used in supplements for senior consumers due to their high-biological value. These proteins are also important sources of bioactive peptides with potential benefits to older adults. However, caseins are known as “slow proteins” because of their digestion kinetics, which are directly linked to the properties of casein micelles. Because older adults naturally have slower digestion, modifying the structural organization of these micelles is a promising strategy to tailor their digestion. This approach could ultimately enhance muscle mass maintenance and optimize bioactive peptide release in senior population. Non-thermal technologies, such as pulsed light (PL), can induce structural changes in casein and modify its susceptibility to gastrointestinal proteolysis. Thus, this study aimed to evaluate the effect of PL treatments on casein proteolysis during in vitro digestion under elderly conditions. Casein powder was subjected to PL treatment at intensities of 10P, 20P, and 40P, while an untreated sample served as control (CT). Samples were dispersed in ultrapure water at 3% (w/v) and submitted to in vitro digestion following the INFOGEST protocol under older adults’ conditions. Proteolysis was evaluated at different digestion stages by measuring absorbance at 280 nm following 3 kDa ultrafiltration and by the trichloroacetic acid (TCA) solubility index, determined after protein precipitation with 10% TCA and protein quantification using the Lowry method. Experiments were performed in triplicate, and data were analyzed by ANOVA followed by Tukey's test (p < 0.05). No significant differences in absorbance at 280 nm were observed in undigested samples or at the end of the gastric phase. At the end of the intestinal phase, 40P showed significantly higher absorbance than CT (0.593 vs. 0.496), while 10P and 20P were intermediate and did not differ from either treatment. This indicates that the highest PL intensity increased low-molecular-weight soluble fraction (< 3 kDa) containing aromatic residues after intestinal digestion, an indirect indicator of soluble peptides. The TCA solubility index revealed the effect of PL treatment on the release of TCA-soluble compounds both in the undigested product and throughout digestion. In the undigested product, a significant effect of PL was observed from 20P onwards. Throughout digestion, this difference was already detected at 10P and became progressive, with greater proteolysis in samples subjected to 40P. Overall, 40P produced the most intense proteolysis, suggesting that the highest PL intensity caused the greatest change in casein susceptibility to enzymatic hydrolysis. These results show that PL alters casein digestion, especially at the highest intensity (40P). Thus, PL is promising strategy to modulate micellar casein’s proteolysis during digestion, highlighting its potential to maximize the health-promoting effects of caseins in senior nutrition.