Heat-induced changes in lactose hydrolysed milks

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Doctoral thesis (article-based)
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Date
2008
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Language
en
Pages
Verkkokirja (2059 KB, 74 s.)
Series
TKK dissertations, 125
Abstract
Carbohydrate reduced lactose hydrolysed milks (CRHM) tasting the same as normal milk have become very popular in several countries. Hitherto their quality during manufacturing and storage has not been studied very closely and compared to the quality of traditional lactose hydrolysed milk (HM) or unhydrolysed milk (UM). The changes caused by the Maillard reactions and proteolysis were followed in different types of lactose hydrolysed skim milks. Lactose hydrolysed milk is highly vulnerable to Maillard reactions and therefore its nutritional quality is often impaired due to the reactions between free amino groups of lysine and reducing sugars. The molar quantity of reducing sugars in HM is almost twofold that in UM. The early stages of Maillard reactions were followed by measuring furosine, which can be released from the Amadori products of lysine and reducing sugars. The blockage of lysine was estimated on the basis of furosine. Pasteurization of lactose hydrolysed skim milk caused only a small increase in furosine compared to UM. In more intensive heat treatments, ESL- and UHT-treatment, furosine formation was more intensive and was found to be closely related to the level of reducing sugars in lactose hydrolysed milk. The hydrolysis products of lactose, i.e. glucose and galactose, were more reactive than lactose in the Maillard reactions occurring during UHT-treatment. As their taste is also sweeter than that of lactose, reduction of the content of monosaccharides in milk improves the nutritional quality of proteins and at the same time preserves the original taste of milk. The almost total removal of lactose with a chromatographic process reduced the blockage of lysine to a negligible level and improved the nutritional value of protein in carbohydrate free milk (CFM) during storage compared to HMs. Proteolysis in lactose hydrolysed UHT-milks is a common problem caused by the indigenous plasmin enzyme system in milk, proteases of contaminating microbes or side activities of the lactase enzyme preparation used. The proteolytic changes and Maillard reactions occurring in lactose hydrolysed milk were largely avoided by separating lactose from milk proteins in a chromatographic process and at the same time subjecting the protein fraction to a heat treatment largely inactivating the proteolytic enzymes. UHT-milk made from fractionated milk protein (CFM) had a longer shelf life than traditionally manufactured HM.
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Keywords
lactose hydrolysed milk, furosine, available lysine
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Parts
  • [Publication 1]: Paul Jelen and Olli Tossavainen. 2003. Low lactose and lactose-free milk and dairy products – prospects, technologies and applications. Australian Journal of Dairy Technology, volume 58, number 2, pages 161-165. © 2003 Dairy Industry Association of Australia (DIAA). By permission.
  • [Publication 2]: O. Tossavainen and H. Kallioinen. 2007. Effect of lactose hydrolysis on furosine formation in skim milk during pasteurisation. Milchwissenschaft, volume 62, number 2, pages 188-191. © 2007 AVA Agrar-Verlag Allgäu. By permission.
  • [Publication 3]: H. Kallioinen and O. Tossavainen. 2008. Changes during storage of lactose hydrolysed extended shelf life (ESL) milk. Milchwissenschaft, accepted for publication. © 2008 AVA Agrar-Verlag Allgäu. By permission.
  • [Publication 4]: O. Tossavainen and H. Kallioinen. 2007. Proteolytic changes in lactose hydrolysed UHT milks during storage. Milchwissenschaft, volume 62, number 4, pages 410-415. © 2007 AVA Agrar-Verlag Allgäu. By permission.
  • [Publication 5]: O. Tossavainen and H. Kallioinen. 2008. Effect of lactose hydrolysis on furosine and available lysine in UHT skim milk. Milchwissenschaft, volume 63, number 1, pages 22-26. © 2008 AVA Agrar-Verlag Allgäu. By permission.
  • [Publication 6]: O. Tossavainen and H. Kallioinen. 2008. Furosine formation and proteolytic changes in carbohydrate reduced UHT milks. Milchwissenschaft, accepted for publication. © 2008 AVA Agrar-Verlag Allgäu. By permission.
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