Focus on the supramolecular structure of milk fat in dairy products

Abstract

-Bovine fat is dispersed in raw milk as natural milk fat globules, with an average diameter of 4 µm, which are enveloped in a biological membrane, the milk fat globule membrane (MFGM). However, dairy processes modify the supramolecular structure and the surface composition of milk fat. Thus, milk fat is present in many dairy products under various forms. In this study, we focused on the fact that natural milk fat globules are rarely consumed in their native state, i.e. in fresh raw milk. In most drinking milks, fat globules are homogenised in order to avoid their rising at the surface of the products. Furthermore, fat globules are heat treated to avoid the growth of micro-organisms. As a consequence of the technological process applied, the volume-weighted average diameter of fat globules in drinking milks is in the range 0.2-0.5 µm. Homogenisation of fat globules led to the partial disruption of the MFGM and to the adsorption of milk proteins. Moreover, this study showed that in cheeses, milk fat can be dispersed as (i) fat globules with the MFGM, (ii) aggregates of fat globules, (ii) homogenised fat globules, (iii) free fat and (iv) a combination of different phases and structures. The knowledge of the supramolecular structure of milk fat in dairy products is of primary importance regarding its technological, sensorial and nutritional properties. milk fat / microstructure / confocal laser scanning microscopy

Impact of ultrasound on dairy spoilage microbes and milk components

“…The homogenisation of fats caused by ultrasonication leads to a decrease in the fat globule size, with a subsequent increase in the surface area of fat globules. The MFGM (milk fat globule membrane) is disrupted during ultrasonication [26]. The MilkoScan uses an infra-red light-based method and the increase in the surface area leads to higher fat content readings.…”

Gangliosides in dairy products: Milk sphingolipids

“…One of them, homogenization, is defi ned as the process of subdividing the relatively large polydisperse oil globules of a coarse oil-in-water emulsion into large number of smaller globules of narrow size range. It results in the most profound changes in the physical structure of milk, such as the decrease in fat globules and changes in fat globule surface composition (LOPEZ, 2005). As homogenization does not kill microorganisms, intensive heat treatments (pasteurization or UHT, ultra-high temperature process) are necessary in order to preserve product microbiological quality.…”

Queijo Parmesão: caracterização físico-química, microbiológica e microestrutura

“…De acordo com Lopez (2005), a funcionalidade do queijo é influenciada pela concentração, pelo tamanho e pela forma dos glóbulos de gordura, bem como pela estrutura destes no leite fluido. Os lipídios se apresentam no leite como uma emulsão; contudo, sua microestrutura nos produtos lácteos e, particularmente no queijo, é pouco conhecida.…”

“…O menor valor foi 3,26% ± 0,11, encontrado na amostra L 2 aos 30 dias, e o maior valor na amostra L 1 , com 12,30% ± 0,15 após (Figura 7a, b), os glóbulos de gordura apresentam tamanhos maiores quando comparados àqueles observados nos demais períodos (Figuras 7f, g, h, i). Possivelmente, o surgimento dos pequenos glóbulos de gordura pode ser consequência da ação de lipases microbianas ativas na matriz do queijo durante a maturação (COLLINS; McSWEENEY; WILKINSON, 2003) e/ou provenientes do tratamento aplicado no processamento desse derivado lácteo (LOPEZ, 2005;LOPEZ;CAMIER;GASSI, 2007). Embora o tratamento térmico do leite seja indispensável para garantir a qualidade sanitária na fabricação de queijos, quando é realizado de forma severa, pode afetar a estrutura do coágulo, sendo perceptível, mais tarde, na microestrutura do produto (PEREIRA; GOMES; MALCATA, 2009).…”