Formation and properties of the whey protein/κ-casein complexes in heated skim milk - A review Laurence Donato, Fanny Guyomarc’H To cite this version: Laurence Donato, Fanny Guyomarc’H. Formation and properties of the whey protein/κ-casein com- plexes in heated skim milk - A review. Dairy Science & Technology, EDP sciences/Springer, 2009, 89 (1), pp.3-29. hal-00895696 HAL Id: hal-00895696 https://hal.archives-ouvertes.fr/hal-00895696 Submitted on 1 Jan 2009 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Dairy Sci. Technol. 89 (2009) 3–29 Available online at: c INRA, EDP Sciences, 2009 www.dairy-journal.org DOI: 10.1051/dst:2008033 Review Formation and properties of the whey protein/κ-casein complexes in heated skim milk – Areview Laurence Donato1,FannyGuyomarc’h2,3* 1 Nestlé Research Center, P.O. Box 44, 1000 Lausanne 26, Switzerland 2 INRA, UMR 1253, Science et Technologie du Lait et de l’Œuf, 65 rue de St Brieuc, 35000 Rennes, France 3 Agrocampus Ouest, UMR 1253, Science et Technologie du Lait et de l’Œuf, 65 rue de St Brieuc, 35000 Rennes, France Received 26 May 2008 – Accepted 3rd November 2008 Abstract – The formation of complexes between whey proteins and κ-casein during heat treat- ment of milk dramatically affects the protein organisation in both the colloidal casein and the serum phases of milk and consequently, its technological applications. This paper reviews the composition and building interactions of these complexes and their localisation between the casein micelle and lactoserum. The currently proposed mechanisms that lead to their formation are also presented. The physico-chemical properties of these complexes, in terms of structure, size and surface properties are described and the technological means by which these properties could be controlled are dis- cussed. Finally, the current hypotheses that explain the functional properties of these complexes in the heat-induced changes of dairy applications are reviewed, with emphasis on acid gelation of milk. heat treatment / whey protein / κ-casein / complex 摘要 – 热处理脱脱脂脂乳乳中中中乳乳清蛋白/κ-酪蛋白复合物的形成和特性——综述。由于热处理导 致的乳清蛋白/κ-酪蛋白复合物的形成严重影响了酪蛋白胶体和乳清蛋白的组织状态及其应 用特性。 本文综述了乳成分、复合物交互作用产生的原因、以及复合物在酪蛋白胶束和乳 清之间的定位。概述了乳清蛋白/κ-酪蛋白复合物形成机理; 描述了复合物的结构、颗粒形 状、尺寸和表面特性等物理化学性质; 以及控制复合物特性的技术方法。最后, 阐述了热诱 导的复合物在乳品加工中的作用, 特别是对酸凝胶形成的作用。 热处理 / 乳清蛋白 / κ-酪蛋白 / 复合物 Résumé – Formation et propriétés des complexes protéines sériques/caséine κ dans le lait écrémé traité thermiquement. Revue. La formation de complexes entre les protéines sériques et la caséine κ au cours du traitement thermique du lait modifie profondément l’organisa- tion des protéines dans la phase caséine micellaire et dans le lactosérum, et par conséquent ses aptitudes technologiques. Cet article fait l’état de l’art de la composition, des interactions impliquées dans les complexes et de leur localisation entre caséine micellaire et lactosérum. * Corresponding author (通讯作者): [email protected] Article published by EDP Sciences 4 L. Donato, F. Guyomarc’h Les mécanismes actuellement proposés pour décrire la formation de ces complexes sont présen- tés. Les propriétés physico-chimiques des complexes, telles que leur structure, leur taille et leurs propriétés de surface, sont décrites et les moyens technologiques permettant de moduler ces pro- priétés sont discutés. Enfin, les hypothèses actuellement proposées pour expliquer les propriétés fonctionnelles des complexes au cours des procédés de transformation du lait sont exposées, avec une attention particulière pour la gélification acide du lait. traitement thermique / protéine sérique / caséine κ / complexe 1. INTRODUCTION (whey, whey protein isolates) as well as in model systems of individual proteins, espe- β Milk proteins are commonly divided be- cially -lactoglobulin [15,20,25,38,39,43, tween caseins and whey proteins, corre- 56,61,65,85–87,92,108,109,140,141,156, sponding, respectively, to about 80 and 165, 179, 191]. However, the simple com- 20% of the total protein. Caseins are es- parison of heat-treated whey and skim milk sentially composed of four different types, strongly suggests that the presence of ca- seins, especially κ-casein, dramatically af- namely the κ, αs1, αs2 and β caseins. In milk biological conditions, the casein fects the characteristics of the heat-induced molecules associate to form supramolec- protein complexes in milk [21, 51, 151]. ular assemblies named casein micelles, Since the publication of earlier reviews which are in dynamic equilibrium with the by Hill [84]andSawyer[167], significant soluble phase of milk. Whey proteins have advances have been made in understand- a globular structure and essentially include ing the formation and properties of whey β-lactoglobulin, α-lactalbumin, blood pro- protein/κ-casein complexes in heated milk. tein immunoglobulins, and Bovine Serum The present state of the art therefore aims Albumin [100, 193]. When milk is heat- at updating this knowledge. First, the loca- ◦ treated at temperatures of ∼ 60 Cand tion and composition of these complexes above, the whey proteins unfold, irre- will be described in milk, and the pro- versibly denature [80, 148, 149, 159]and posed pathways that may yield to their eventually aggregate through hydrophobic formation will be discussed. The struc- bonding and thiol/disulphide exchanges tural and physico-chemical properties of with themselves and with, essentially, the whey protein/κ-casein complexes will κ-casein, leading to the so-called whey then be described, taking their possible in- protein/κ-casein complexes [70, 95, 135, trinsic variations into account. The forma- 171, 176]. tion of whey protein/κ-casein complexes Heat treatment is applied in many dairy affects many dairy processes such as, e.g., processes either to enhance desirable prop- cheesemaking and recovery of the whey erties of the products, such as texture and protein [69], yoghurt-making [41, 123], taste, or to ensure its safety and shelf-life. storage of UHT milks [129] and prepa- Heat-treated milk proteins have interesting ration of functional ingredients. To im- functional properties that are widely ap- prove these processes, technological strate- plied in food, cosmetics or pharmacy. In gies must therefore be grounded on an the last few decades, extensive research extensive knowledge of the properties of has been dedicated to the understanding of the whey protein/κ-casein complexes. Fi- the heat-induced aggregation of denatured nally, further possible prospects for re- whey proteins in milk or in its fractions search and application will be proposed. Whey protein/κ-casein heat-induced complexes 5 2. FORMATION OF κ-CASEIN/ 70] (see also Sect. 2.2). Whey proteins WHEY PROTEIN COMPLEXES added to skim milk are incorporated into IN HEATED MILK the complexes on heating [28, 29, 51, 176] while unreacted κ-casein has been found 2.1. Composition and building in milk after heat treatment [51, 70, 152]. interactions of the complexes These results indicate that the whey pro- teins, and especially β-lactoglobulin, are 2.1.1. Composition of the heat- the reaction-limiting proteins to the growth induced protein complexes of the heat-induced complexes in milk. in milk Early studies have long demon- 2.1.2. Covalent binding through strated that model mixtures of isolated thiol/disulphide interchanges β-lactoglobulin and κ-casein yielded co- valent complexes through thiol-disulphide Only recently, mass spectroscopy exchanges on heat treatment [46, 128, 195] has been applied to skim milk and that may even gel at sufficient protein β-lactoglobulin/κ-casein mixtures to try concentration [47]. In skim milk or re- to identify the intermolecular disulphide constituted skim milk systems, covalent bonds that are formed on heat treatment. complex formation between κ-casein In all studies, Cysteine 160 (Cys 160) and β-lactoglobulin has also been clearly of β-lactoglobulin was implicated in the demonstrated [95, 134, 135, 171, 176]and formation of intermolecular disulphide evidence has also been presented that bridges, e.g. with κ-casein on the surface α-lactalbumin is significantly involved of goat’s milk casein micelles [83], with in these complexes [33, 105, 134, 135], κ-casein in either the micelle or serum most likely through similar mediation phase of heated skim milk [116] and with of β-lactoglobulin like that reported in κ-casein in model protein mixtures [116], model systems [48]. To a minor extent, as well as with other β-lactoglobulin BSA, lactoferrin [33, 50, 105, 161]and molecules (i.e. involving other Cys than αs2-casein, containing two disulphide intramolecular-bound 66) in heated model bridges [70, 133, 150], are also involved protein solutions [32, 114, 115, 178]. in these complexes via thiol/disulphide Livney and Dalgleish [114] found that exchanges. Immunoglobulins were sus- Cys 119/121 of β-lactoglobulin was pected to partially associate with the involved in intermolecular bonds with complexes through hydrophobic interac- all the other possible cysteines of both tions only [139, 141]. In serum complexes κ-casein and β-lactoglobulin.