Effect of protein hydrolysis on physical properties and antioxidant activities of cow is milk

Name: Sasiprapa Vanitcharoen

Address: 333 Moo1, Thasud, Muang, Chiang Rai 57100

Organization : School of Agro-Industry, Mae Fah Luang University

Email : ask.library@mfu.ac.th

Name: Nattapol Tangsuphoom

Name: Uthaiwan Suthisansanee

Name: Chalat Santivarangkana

keyword: Antioxidant activity - Enzymatic hydrolysis - Hydrolyzed milk protein - Milk - Protease

ThaSH: Food sciences

ThaSH: Agricultural industries

ThaSH: Antioxidants

ThaSH: Enzymes

ThaSH: Hydrolysis

ThaSH: Milk

ThaSH: Protease inhibitors

Abstract: hydrolysates and peptides are known for their health benefits, particularly antioxidative effects. The aim of this study is to determine the physical properties and antioxidant activities of cow’s milk subjected to enzymatic hydrolysis. Pasteurized skim milk (3.5% protein) was hydrolyzed by adding Alcalase 2.4L, Protamex 1.5MG, Flavourzyme 1000L or porcine trypsin at the enzyme-to-substrate ratios of 0.1-1% (w/w). Hydrolysis was conducted for ≤8 h at refrigerated (4ºC), and enzyme’s optimal temperatures (50ºC, except 37ºC for trypsin) prior to heating at 72ºC for 3 min and immediate cooling to inactivate the enzyme. Progress of hydrolysis was monitored by determining the degree of hydrolysis (DH). Color values (L*, a*, b*), total color difference against non-hydrolyzed milk (ΔE*), pH, and physical stability of the hydrolyzed samples were measured. Antioxidant activities were determined as ferric reducing antioxidant power (FRAP) and oxygen radical absorbance capacity (ORAC). DH of hydrolyzed milk increased with enzyme concentration, hydrolysis temperature, and time. The highest DH of 25% was observed in samples hydrolyzed with Alcalase, followed by Flavourzyme, Protamex and trypsin. L*, a* and pH values of milk were unaffected by hydrolysis. Protein hydrolysis of milk led to the increase in b* and the samples prepared with trypsin showed the highest ΔE*. Hydrolysis with Alcalase or trypsin resulted in phase separation of the milk, especially at high DH. Only Protamex- and Flavourzyme-hydrolyzed milk with 10-20% DH, in which separation was absent, were analyzed for antioxidant activities. FRAP and ORAC of non-hydrolyzed milk were 17.71 and 177.02 µmol TE/ml, respectively and the values increased with DH. At any similar DH, Protamex-hydrolyzed milk showed higher FRAP than those hydrolyzed with Flavourzyme, which had higher ORAC value. The highest FRAP (25.23 µmol TE/ml) and ORAC (262.65 µmol TE/ml) were obtained by hydrolysis with 0.5% Protamex at 50ºC for 30 min and 1% Flavourzyme at 50ºC for 90 min, respectively. Our findings indicated that enzymatic hydrolysis of protein under suit able condition could slightly improve the antioxidant activities of cow’s milk, while causing minimal changes in physico-chemical characteristics as compared with non-hydrolyzed milk.

Mae Fah Luang University. Learning Resources and Educational Media Center

Address: CHIANG RAI

Email: library@mfu.ac.th

Modified: 2021-10-19

Issued: 2021-10-19

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Journal of Food Science and Agricultural Technology (2018) Vol.4 (Spcl. Iss.): 105-110

eng

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