Browsing by Subject "Homogenization"

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    Homogenization improves foaming properties of insoluble pea proteins
    (2022) Moll, Pascal; Salminen, Hanna; Griesshaber, Elena; Schmitt, Christophe; Weiss, Jochen
    Foams are essential in many food applications and require surface-active ingredients such as proteins for formation and stabilization. We investigated the influence of high-pressure homogenization on foaming properties of insoluble pea protein dispersions (5% w/w) at pH 3 and 5. Unhomogenized insoluble pea protein dispersions did not foam at either pH 3 or 5, as they consisted of large insoluble pea protein aggregates with limited surface activity. At pH 3, the homogenized pea protein dispersions generated foams due to higher protein solubility and surface activity through disruption of large protein aggregates into smaller particles. The foam stability decreased with increasing homogenization pressure and number of cycles due to a reduction in continuous phase viscosity. At pH 5, the insoluble pea proteins foamed when the homogenization resulted in formation of aggregates made of smaller protein entities, which was the case for homogenization ≥ 100 MPa and three cycles. In general, the foam capacity (amount of formed foam) was higher at pH 3 due to improved protein solubility and surface activity that facilitated incorporation of air, while the foam stability (resistance against foam collapse) was better at pH 5 because of the presence of larger protein aggregates that formed thicker and more viscous films around the air bubbles benefitting retention of gas bubbles. Overall, homogenization improved the foaming properties of insoluble pea proteins at pH 3 and 5.
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    The impact of milk properties and process conditions on consistency of rennet-coagulated curd and syneresis of rennet curd grains
    (2008) Thomann, Stephan; Hinrichs, Jörg
    Although cheesemaking is an ancient art, modern cheese production relies on the implementation of innovative technology and tailor-made starter bacteria to remain competitive in the production of commodity-type cheeses such as soft and semi-hard cheese. Any intervention in the cheesemaking procedure, i.e. in milk composition, milk treatment and microbial fermentation, affects textural properties of curd at cutting and finally syneresis. The latter is the key step in cheesemaking since the degree of syneresis determines the moisture content of the raw cheese, by which ripening as well as rheological properties and sensory are affected. This work aimed to investigate the syneresis of rennet curd grains in order to generate a kinetic model for predicting syneresis. On the one hand, the experiments covered the implementation of EPS-(exopolysaccharide producing) cultures in the manufacture of soft cheese and likewise the investigation of the cheesemaking potential of Dahlem Cashmere goat?s milk. On the other hand, the interrelated effects of homogenization, microfiltration and pH on rheological properties of rennet-induced milk gels, on syneresis and finally on cheese composition, yield and functionality were to study. Three mathematical models were compared for their suitability describing syneresis and providing kinetic parameters. The kinetic parameters obtained by a linearised model gave best curve fittings to the experimental data with high coefficient of correlation (r² > 0.99). Furthermore, the model provides a parameter (RWRmax) that gives information about the endpoint of syneresis. From this value, interpretation about the curd structure and the interaction of milk composition and physical factors on syneresis is possible. Fermentation media inoculated with non-EPS-producing Streptococcus thermophilus and EPS-producing strains of Lactococcus lactis subsp. cremoris and Lactobacillus sakei were added in a concentration from 5 % to 10 % (w/w) to the milk prior to soft cheese manufacture. The cheesemaking experiments showed that the addition of fermentation media with EPS-cultures retarded syneresis, accelerated microbial fermentation and finally caused ripening problems. By means of model experiments regarding syneresis and influence of pH value, the manufacture of soft cheese was technologically adapted. The approach demonstrated that soft cheese manufacture was yet feasible and moisture content of the raw cheese was increased by the addition of fermentation media, inoculated with EPS-cultures. Analysis of variance revealed that syneresis was significantly affected by homogenization, MF and pH. It was shown that milk composition and MF markedly influenced the endpoint of syneresis, RWRmax. Curd grains made from skim milk had the highest RWRmax value. It is assumed, that differences in curd microstructure due to fat globule distribution and content affect syneresis since cutting was performed at equal curd firmness. The experiments demonstrate that homogenization and MF can be combined to reach curd firmness and syneresis which are in accordance with values in conventional cheesemaking. Combination of homogenization and MF was promising on cheese yield, and based on the results and experience gained in this study, a new and simplified process for semi-hard cheesemaking was invented. It was shown, that the adjusted cheese yield and component recovery increased due to the interaction of homogenization and MF. Hence, the combination of homogenization and MF in cheese manufacture is promising.