Heat-induced interactions of β-lactoglobulin and α-lactalbumin with the casein micelle in pH-adjusted skim milk

Oldfield, David J.; Singh, Harjinder; Taylor, M. W.; Pearce, K. N.

doi:10.1016/s0958-6946(00)00087-x

Cited by 125 publications

(82 citation statements)

References 29 publications

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“…Only 58% and 40% of these denatured proteins associate with casein micelles, respectively [29]. The behaviour of a-LA and b-LG are dependent upon the time of heating, the temperature, the pH and the amount of proteins [5,25]. After heating at 85°C for 10 min, a marked increase in the concentration of k-casein (k-CN) in the supernatant has been reported (from 15 in unheated to 23% of total k-CN in heated milk) [18], but it should be noted that increasing the pH value to 7.1 leads to a greater concentration of supernatant casein in the milk heated to 70-80°C [2].…”

Section: Introductionmentioning

confidence: 99%

Fermentation by lactic acid bacteria at two temperatures of pre-heated reconstituted milk. I - Behaviour of proteins and minerals

Laligant

Famelart

Brulé³

et al. 2003

Lait

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-The pH-induced physico chemical changes in a reconstituted heated (90°C -10 min) skim milk were studied during fermentation by lactic acid bacteria at two temperatures (30°C and 42°C). Different variables were examined during acidification: the water content of ultracentrifugation pellets (150000 g for 70 min at 30 or 42°C), the partition of proteins into pelleted and unpelleted fractions (analysed by RP-HPLC on supernatants) and the dissociation of colloidal salts (determined by atomic absorption spectrophotometry on the ultrafiltrates). The proportion of unpelleted protein was found to be pH-dependent with a gradual linear decrease during acidification. All the caseins pelleted below pH 5.5. As the pH was reduced, calcium was progressively released from the micelles. In contradiction with a number of previous findings, fermentation induced a shift toward acid pH values of the salt dissociation compared with a glucono-delta-lactone acidification. The partition of casein between the pellet and the supernatant due to acidification by fermentation was temperature-dependent, as was the solvation of the pellet. Both were greater at 30°C compared with 42°C. The temperature had no effect on the salt distribution. The results are discussed in terms of transfer phenomena between the colloidal and the solvent fractions and diffusion-limited processes. Milk / yoghurt / pH / mineral / micellar solvation / caseinRésumé -Fermentation du lait reconstitué traité thermiquement par des bactéries lactiques à deux températures. I -Protéines et minéraux. L'effet du pH sur les évolutions physicochimiques de lait écrémé reconstitué et traité thermiquement à 90°C, 10 min a été étudié au cours d'une acidification par fermentation lactique à deux températures (30°C et 42°C). La quantité d'eau a été évaluée par séchage des culots d'ultracentrifugation (150000 g pendant 70 min à 30 ou 42°C). La distribution des protéines entre le culot et le surnageant a été analysée par chromatographie RP-HPLC sur les surnageants avec ou sans dithiothreitol. La dissociation des sels colloïdaux a été déterminée par spectrométrie d'absorption atomique dans les ultrafiltrats de lait. La proportion de protéines dans le surnageant était dépendante du pH avec une diminution graduelle au cours de

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Section: Introductionmentioning

confidence: 99%

Fermentation by lactic acid bacteria at two temperatures of pre-heated reconstituted milk. I - Behaviour of proteins and minerals

Laligant

Famelart

Brulé³

et al. 2003

Lait

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“…Unfortunately many different techniques have been used to separate the micellar and serum phases. Centrifugation is the most common but many different conditions have been used, ranging from 175 000× g/60 min to 19 200× g/240 min [2,4,11,17,18,22,29,32,33,[35][36][37]41]. Other researchers have rejected the use of centrifugation on the basis of being too harsh and likely to cause micellar disintegration and have used treatment with rennet to precipitate the micelle fraction instead [38].…”

Section: Resultsmentioning

confidence: 99%

“…Significant influences on the distribution are the pH [3] and time and temperature of heating [29]. There may also be some question over what constitutes both serum and micellar proteins due to the wide range of methods that have been used to separate the micellar from soluble proteins.…”

Section: Investigation Of Aggregation States By Secmentioning

confidence: 99%

Role of protein aggregation in heat-induced heat stability during milk powder manufacture

Williams

D'ath

Zisu

2008

Dairy Sci. Technol.

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-Although the inherent heat stability and the processes leading to the heat-induced coagulation of milk and reconstituted milk powders have been studied extensively, the processes that lead to heat-induced heat stability are less well established. An investigation has been undertaken into the effects of standardization with milk permeate or lactose and the heat-stabilization of milk powders. Standardized and unstandardized milk powders were produced in spring and autumn to determine seasonal effects on their heat stability. Other standardized powders were produced using a range of preheat treatments (85 • C/1800 s, 120 • C/120 s, and 140 • C/5 s) to evaluate the effects of preheat treatment and standardization on the heat stability of milk powders. Micelle size and the soluble aggregates formed during the preheat treatment were characterized by a combination of size-exclusion chromatography and SDS-PAGE. The heat stability of the powders was evaluated in a bench-scale model of retorted recombined evaporated milk manufacture. As has been generally accepted, the heat stability may be mediated by the way in which the milk responds to the preheat treatment given during milk powder manufacture. However, we have found that causing the denaturation of the whey proteins in itself, as is indicated by analytical measures such as the whey protein nitrogen index (WPNI) is not sufficient to impart heat stability. Our work suggests that milks with good heat stability are achieved by heating to give a low WPNI and a balance of moderately sized soluble aggregates and a decrease in the proportion of smaller micelles. The formation of these aggregates is influenced by the heating regime applied and varies at different times of year.heat stability / milk protein aggregation / micellar integrity Résumé -Rôle de l'agrégation des protéines dans la stabilité thermique thermo-induite au cours de la fabrication de poudre de lait. Bien que la stabilité thermique inhérente et les processus conduisant à la coagulation thermo-induite du lait et des poudres de lait reconstituées aient été largement étudiés, les processus qui conduisent à la stabilité thermique thermo-induite sont moins bien établis. Une étude a été entreprise concernant les effets de la standardisation avec du perméat de lait ou du lactose et la stabilisation thermique des poudres de lait. Des poudres de lait, standardisé et non standardisé, ont été produites au printemps et en automne pour déterminer l'effet saison sur leur stabilité thermique. D'autres poudres standardisées ont été produites en appliquant différents prétraitements thermiques (85 • C/1800 s, 120 • C/120 s et 140 • C/5 s) pour évaluer les effets du pré-traitement et de la standardisation sur la stabilité thermique des poudres de lait. La taille des micelles et les agrégats solubles formés au cours du prétraitement thermique ont été caractérisés en combinant chromatographie d'exclusion de taille et électrophorèse SDS-PAGE. La stabilité thermique des poudres était évaluée à l'aide d'un modèle simulant...

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“…A adição de leite ao soro melhorou o rendimento do processo devido à associação das soroproteínas com as micelas de caseína (OLDFIELD et al, 2000). A percentagem de proteína precipitada (Tabela 2) aumentou com a adição de leites pasteurizado e em pó desnatado, assim como o rendimento do processo.…”

Section: Resultsunclassified

Determinação Das Melhores Condições Operacionais Do Processo De Produção Da Ricota

Porto¹,

Santos²,

Miranda³

2005

B. do CEPPA

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Neste trabalho foram analisadas as melhores condições operacionais de produção de ricota, visando avaliar a agregação de valor desse processo ao soro do queijo e diminuição de seu potencial poluente. Desenvolveu-se planejamento fatorial 2 3 , considerando as seguintes variáveis: tempo de precipitação, temperatura e pH nos quais seria possível a obtenção das ricotas produzidas com soro puro e com adição de leite e leite em pó desnatado ao soro. Os resultados foram analisados em relação à recuperação de proteína existente na mistura inicial (soro+leite), aos teores de lactose e gordura nos soros e a demanda química de oxigênio (DQO) do soro antes e depois da produção para analisar seu efeito poluidor. Obteve-se melhor condição de produção em pH 5,0 e temperatura de 92ºC. O tempo de precipitação não apresentou grande influência no processo e a DQO mostrou-se dependente do teor de lactose do soro. Efetuou-se avaliação da viabilidade econômica do processo com e sem a adição de leite, bem como avaliação sensorial das ricotas economicamente viáveis. Não houve diferença na aceitação entre as ricotas. O leite deve ser adicionado em pequenas quantidades, ainda que com elevação de custo para melhorar as condições de coleta da massa da ricota no processo. PALAVRAS-CHAVE: SORO; QUEIJO; RICOTA.* Parte da dissertação de mestrado da primeira autora.

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Heat-induced interactions of β-lactoglobulin and α-lactalbumin with the casein micelle in pH-adjusted skim milk

Cited by 125 publications

References 29 publications

Fermentation by lactic acid bacteria at two temperatures of pre-heated reconstituted milk. I - Behaviour of proteins and minerals

Fermentation by lactic acid bacteria at two temperatures of pre-heated reconstituted milk. I - Behaviour of proteins and minerals

Role of protein aggregation in heat-induced heat stability during milk powder manufacture

Determinação Das Melhores Condições Operacionais Do Processo De Produção Da Ricota

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