Instant infusion pasteurisation of bovine milk. II. Effects on indigenous milk enzymes activity and whey protein denaturation |
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Authors: | MARIANNE HAMMERSHØJ ANNI B HOUGAARD JANNIE S VESTERGAARD OLE POULSEN RICHARD H IPSEN |
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Affiliation: | 1. Department of Food Science, Faculty of Agricultural Sciences, University of Aarhus, Blichers Allé 20, DK‐8830 Tjele;2. Department of Food Science, Faculty of Life Sciences, University of Copenhagen, Rolighedsvej 30, DK‐1958 Frederiksberg C;3. SPX APV, Pasteursvej 1, DK‐8600 Silkeborg, Denmark |
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Abstract: | Direct heat treatment of two milk types, skimmed and nonstandardised full‐fat, was performed by instant steam infusion and compared with indirect heating. Infusion conditions were temperatures of 72–120°C combined with holding times of 100–700 ms, and indirect heat conditions were 72°C/15 s and 85°C/30 s. The activity of indigenous enzymes such as alkaline phosphatase, lactoperoxidase, xanthine oxidase and γ‐glutamyl transpeptidase was evaluated. Infusion temperature was the main determinant of inactivation. Whey protein denaturation represented by β‐lactoglobulin increased significantly with infusion temperature. The nonstandardised milk had a higher denaturation rate than skimmed milk. The effect of instant infusion on pH and milk fat globule size in relation to whey protein denaturation and association is discussed. |
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Keywords: | Instant infusion pasteurisation Milk Enzymatic activity Whey protein denaturation |
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