Location: Dairy and Functional Foods ResearchTitle: Differential behavior of Lactobacillus helveticus B1929 and ATCC 15009 on the hydrolysis and Angiotensin-I-Converting Enzyme Inhibition activity of fermented UHT milk and nonfat dried milk powder
Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/10/2023
Publication Date: N/A
Interpretive Summary: Fermented foods are receiving growing interest due to their reported health benefits. Research has shown that some milk proteins may alleviate specific conditions, such as hypertension. These properties are often encrypted in the native proteins and require liberation in vivo by gastrointestinal digestion or through fermentation with proteolytic starter cultures (LAB). We fermented UHT milk and reconstituted NFDM, two commercially sourced products, with two Lactobacillus helveticus strains, B1929 and ATCC 15009, and examined their ability to develop antihypertensive activities of the fermentate. We showed that the B1929 performed better than ATCC 15009 to hydrolyze proteins and develop potentially advantageous properties.
Technical Abstract: Consumers’ growing interest in fermented dairy foods necessitates research on a wide array of lactic acid bacterial strains to be explored and utilized. This study aimed to investigate the differences in the proteolytic capacity of Lactobacillus helveticus strains B1929 and ATCC 15009 on the fermentation of commercial ultra-pasteurized (UHT) skim milk and reconstituted nonfat dried milk (NFDM) powder (at a comparable protein concentration, 4%). The antihypertensive properties of the fermented milk, measured by Angiotensin-I-Converting Enzyme Inhibition Activity (ACE-I), were compared. B1929 lowered the pH of the milk to 4.13 ± 0.09 at 37 °C after 24 h, while ATCC 15009 needed 48 h to drop the pH to 4.70 ± 0.18 at 37 °C. Two soluble protein fractions, one (CFS1) obtained after fermentation (acidic conditions) and the other (CFS2) after the neutralization (pH 6.70) of the pellet from CFS1 separation, were analyzed for D-/L- lactic acid production, protein concentration, the degree of protein hydrolysis (DH), and ACE-I activity. CFS1 fractions, dominated by whey proteins, demonstrated a greater DH (7.9%) than CFS2s. On the other hand, CFS2s, mainly casein proteins, showed a higher level of ACE-I activity (33.8%) than CFS1. Significant differences were also found in the D- and L- lactic acid produced by the UHT milk between the two strains. These results attest that milk casein proteins possessed more detectable ACE-I activity than whey fractions, even without a measurable degree of hydrolysis. Findings from this study suggest that careful consideration must be given when selecting the bacterial strain and milk substrate for fermentation.