Adsa Logo White Adsa Title White

Interaction of strawberry phenolic compounds with milk proteins.

R. Singh




Interaction of strawberry phenolic compounds with milk proteins.
R. Singh*, R. Bajaj. NDRI Karnal, Haryana India.

The bioactive properties of polyphenols have gained great importance due to the proven health benefits and incorporating it in milk system can serve as a basis for functional foods. But the question is what happens when they are present together because polyphenols have significant binding affinity to milk proteins, which can lead to the formation of protein-polyphenol complexes and significantly affect biological activities. Therefore, the present investigation is planned to study the interaction of strawberry polyphenols with milk proteins at different protein concentration (1—40 mg/mL), polyphenol concentration (0.5—2 mg/mL), processing temperature (73 C/ no hold and 90 C/15 min 120 C/15 min) and pH values (6.7 and 3.57). The reconstituted skim milk (8.5% SNF) was also prepared to have a combined effect of casein and whey proteins. The results (3 replicates) were analyzed using ANOVA and the Tukey test (P-values ≤0.05). Statistical analysis was performed using Prism software (version 5.01). It was found that binding of polyphenols was highest with casein (30mg/mL) and least with skim milk (8.5% SNF) and increased from 55 to 70% as casein concentration increased from 1 to 10 mg/mL. Antioxidant activity is measured by using DPPH assay. The DPPH activity of polyphenol remain unchanged with skim milk and decreased as protein concentration increased from 1 to 40 mg/mL. Effect of heating at different time-temperature combination had no effect on the binding of polyphenol and antioxidant activity. Increasing the pH of polyphenol from 3.57 to 6.7 resulted in increased antioxidant activity for casein, whey protein and milk-polyphenol system. Further, from spectrofluorimetric analysis of samples, it was observed that hydrophobic sites decreased from 400 to 20 at 8% SNF of milk, from 800 to 80 at 2.5% casein and from 700 to 80 at 2% whey protein from control to the samples blended with polyphenol extract. ANS (fluorescent dye 1-anilinonaphthalene-8-sulphonate) binding affinity decreased from 0.05 to 0.02 at 8% SNF, from 0.04 to 0.03 at 2.5% casein and from 0.06 to 0.05 at 2% whey protein from control to the samples blended with Polyphenol extract. These results will help in designing manufacturing processes of functional dairy products that improve yield and quality attributes.

Keywords: polyphenol, protein, interaction.