High pressure homogenisation of raw whole bovine milk (a) effects on fat globule size and other properties

Abstract

Although widely adopted by the chemical and pharmaceutical industries in recent years, little published data is available regarding possible applications of high pressure homogenisation for dairy products. The objective of this work was to compare the effects of conventional (18 MPa, two-stage) and single or two-stage high pressure homogenisation (HPH) at 50–200 MPa on some properties of raw whole bovine milk (∼4% fat). Fat globule size decreased as HPH pressure increased and, under certain conditions of temperature and pressure, HPH yielded significantly smaller fat globules than conventional homogenisation. Fat globule size was also affected by milk inlet temperature. The pH of all homogenised milk samples decreased during 24 h refrigerated storage. Total bacterial counts of milk were decreased significantly (P<0·05) for milk samples HPH-treated at 150 or 200 MPa. Whiteness and rennet coagulation properties of milk were unaffected or enhanced, respectively, as homogenisation pressure was increased. Average casein micelle size decreased slightly when skim milk was homogenised at 200 MPa. Thus, HPH treatment has several, potentially significant, effects on milk properties.

Pre-treatment of cheese milk: principles and developments

“…The adsorption of caseins onto the fat globules has the following implications for cheese-making characteristics of milk: (1) casein surface area in milk is increased, but the amount of micellar casein is reduced; (2) two types of particles with a casein micelle surface layer exist: native casein micelles and casein-covered fat globules; (3) when adsorbed, casein micelles tend to spread over the surface of the fat globule and hence increase in effective surface area but with reduced surfacedensity of κ-casein. The rennet coagulation time (RCT) of unhomogenised milk is generally lower than that of homogenized milk [57,62,135,149]. This is probably related to the larger casein surface area in homogenized milk, as well as the lower surface density of κ-casein.…”

“…The former increases the probability of interactions between particles, whereas the latter, for a subclass of particles, reduces the amount of κ-casein that needs to be hydrolyzed before micellar flocculation is induced. Conflicting reports exist on the influence of homogenization on the rate of rennet-induced gel formation; both homogenization-induced increases [57,62,149] and decreases [135] therein have been reported. Zamora et al [149] reported that, on high-pressure homogenization (100-330 MPa), the rate of gel formation may be either increased or decreased, with no clear trend as a function of homogenization pressure, but large differences in the pH of samples hinder a clear and unequivocal interpretation of these data.…”

Inactivation of two strains ofEscherichia coliinoculated into whole and skim milk by ultrahigh-pressure homogenisation

“…Ultrahigh-pressure homogenisation UHPH (also called dynamic high pressure in the literature) is based on the same design principles as conventional homogenisation processes that are used in the dairy industry for reducing the size of fat globules [10,22,23], but working at significantly higher pressures (> 200 MPa), resulting in the destruction of large quantities of microorganisms. Consequently, this technology appears to be an important means of lowering the initial microbial load while helping to minimise product damage from unnecessary heat stress [17].…”

Impacto De Nuevas Tecnologías De Conservación Sobre La Estructura Y Los Principales Componentes Químicos De Alimentos Fluidos

“…Por otra parte, al reducirse el tamaño del glóbulo de grasa y aumentar su área superficial, junto con el aumento de temperatura asociado al tratamiento, podría incrementarse la susceptibilidad de la grasa de la leche a la lipólisis y la oxidación lipídica, por acción de las enzimas de la leche (Hayes y Kelly, 2003bKelly, y 2005 Pereda et al, 2008a Pereda et al, y 2008b, con la consecuente disminución de pH del medio. Pereda et al (2008a) observaron una mayor lipólisis en leche tratada a presiones más bajas (200 MPa) por la actividad lipolítica residual, mientras que la oxidación lipídica fue mayor a 300 MPa, posiblemente debido a la temperatura alcanzada Introducción 23 (100ºC).…”

“…Además, esta disminución de tamaño se ve afectada por la temperatura de entrada (Datta et al, 2005) y la aplicación de un segundo ciclo de homogeneización (Thiebaud et al, 2003; Hayes y Kelly, 2003b). Por otra parte, durante la homogeneización, se altera también la composición de la membrana nativa de los glóbulos de grasa por adsorción principalmente de caseínas y proteínas del suero en la interfase (Cano-Ruiz y Richter, 1997; Michalski y Januel, 2006).Sin embargo, se ha observado que a partir de una determinada presión (>250 MPa, 300 MPa), se produce la coalescencia de los glóbulos de grasa, posiblemente debida a la mayor superficie de exposición grasa e insuficiente cantidad de proteína (principalmente caseínas) para estabilizarla, a que se comparten constituyentes proteicos entre distintos glóbulos lo que provoca la aglomeración de los mismos o al efecto de HPH sobre las proteínas que perjudica sus propiedades emulsionantes (Thiebaud et al, 2003;Hayes et al, 2005; Pereda et al, 2007).Por otra parte, al reducirse el tamaño del glóbulo de grasa y aumentar su área superficial, junto con el aumento de temperatura asociado al tratamiento, podría incrementarse la susceptibilidad de la grasa de la leche a la lipólisis y la oxidación lipídica, por acción de las enzimas de la leche (Hayes y Kelly, 2003bKelly, y 2005 Pereda et al, 2008a Pereda et al, y 2008b, con la consecuente disminución de pH del medio. Pereda et al (2008a) observaron una mayor lipólisis en leche tratada a presiones más bajas (200 MPa) por la actividad lipolítica residual, mientras que la oxidación lipídica fue mayor a 300 MPa, posiblemente debido a la temperatura alcanzada Introducción 23 (100ºC).…”