Microstructural and textural properties of rennet-induced milk protein gel: Effect of guar gum

The knowledge of the effect of polysaccharide addition on the textural properties of milk protein gels is important for foodstuff engineering design. Therefore, the microstructure, texture, and water-holding capacity of rennet-induced milk protein gel with and without the addition of different concentrations of guar gum (GG) were determined. It was found that the presence of GG changed the microstructure of rennet-induced milk gel. The addition of a GG concentration higher than 0.075% w/v led to a discontinuous protein network. Changes in the structure of the gel samples are reflected in the texture perception and their capability of water retention. When a limit GG concentration of 0.15% w/v was exceeded, a very weak gel sample was obtained. The results demonstrated that different milk protein gel microstructures can be created by the addition of different concentrations of GG.Fil: Galante, Micaela. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmaceuticas. Departamento de Química y Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario; ArgentinaFil: Boeris, Valeria. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmaceuticas. Departamento de Química y Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario; Argentina. Pontificia Universidad Católica Argentina "Santa María de los Buenos Aires"; ArgentinaFil: Alvarez, Estela Mari. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmaceuticas. Departamento de Química y Física; ArgentinaFil: Risso, Patricia Hilda. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmaceuticas. Departamento de Química y Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario; Argentina. Universidad Nacional de Rosario. Facultad de Ciencias Veterinarias; Argentin

Studying stirred yogurt microstructure and its correlation to physical properties : a review

Microstructure is an important part of the understanding and the control of food properties as rheological properties, water holding and sensory properties. Stirred yogurt microstructure is being under study for decades. Observations at several length scales have been used to probe the structure. Some methods using optical techniques were recently introduced to provide a quick microstructure assessment of stirred yogurt. This review aims to provide a description of stirred yogurt microstructure and a short overview of the main techniques to characterize stirred yogurt microstructure allowing to highlight their complementarity. In general, stirred yogurt microstructure is described as a suspension of interconnected microgels into a continuous serum phase. While the relationship between yogurt microstructure and its physical and sensory properties has been discussed in numerous reviews, models or studies the impact of microgels sizes on rheological properties, water holding capacity, and creaminess, has not always been confirmed. Even if, other features such as microgels aggregation, shape, and compaction have shown to be involved in sensory or physical properties of stirred yogurt gel, a challenge remains for the characterization of microstructural characteristics of microgels without destructuring the network

Physical-mathematical model to predict the kinetic coagulation process by clotting activity of bacterial endopeptidases

A physical-mathematical model was used to evaluate the capability of an enzymatic pool of Bacillus sp. P7 (isolated from Piaractus mesopotamicus) to promote the bovine casein micelles coagulation. Experiments were designed to assess the effects of temperature, pH, and enzyme activity/mass of substrate ratio on the kinetic parameters of the coagulation process and the microstructure of the obtained clots. Descriptive and predictive equations indicate that the temperature and the pH modified these parameters significantly. In optimal conditions, the clot’s mean pore size was 3.6 times smaller using chymosin. On the other hand, rheological measurements evidence a moderate elasticity of clot, which indicates the usefulness of P7 protease preparation as a clotting agent in spreadable or soft cheese manufacture. Also, the hydrolysis products, which are in the whey after casein micelles coagulation, demonstrated antioxidant activities. Equations to model and predict the process kinetics were combined with rheological and microstructure analyses of the obtained clots, and whey bioactivities were evaluated. Nevertheless, the use of P7PP requires further investigation concerning the stability of the enzyme preparation during storage, its performance, and how these variables could be related to the proposed models.Fil: Mancilla Canales, Manuel Arturo. Grupo de Física Biomédica. Instituto de Física Rosario (CONICET-UNR); Argentina.Fil: Riquelme, Bibiana Doris. Grupo de Física Biomédica. Instituto de Física Rosario (CONICET-UNR); Argentina.Fil: Mancilla Canales, Manuel Arturo. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas; Argentina.Fil: Riquelme, Bibiana Doris. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas; Argentina.Fil: Risso, Patricia Hilda. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas; Argentina.Fil: Folmer Côrrea, Ana Paula. Universidade Federal de Rio Grande do Sul. Instituto de Ciência e Tecnologia de Alimentos; Brasil.Fil: Brandelli, Adriano. Universidade Federal de Rio Grande do Sul. Instituto de Ciência e Tecnologia de Alimentos; Brasil.Fil: Risso, Patricia Hilda. Universidad Nacional de Rosario. Facultad de Ciencias Veterinarias; Argentina

Microstructural and textural characteristics of soy protein isolate and tara gum cold-set gels

Soy protein isolates (SPI) are capable of forming cold-set gels. This techno-functional property can be affected by the presence of tara gum (TG). Under certain conditions, these SPI/TG systems may also form water-in-water (W/W) emulsions. The aim of this study was to evaluate acid gels formed from soy protein isolates (SPI) and tara gum (TG) aqueous mixtures, and to find the conditions in which the W/W emulsions of SPI droplets dispersed in a TG continuous phase can be stabilized by SPI gelation as a strategy to prevent emulsion destabilization. Cold-set gels of SPI 0.3 g/L at different TG concentrations (0–0.05 g/L) showed different microstructures, a consequence of a different balance between gelation and segregative phase separation processes. SPI gels showed a homogenous and compact microstructure. When TG was present at 0.01 g/L and 0.02 g/L, the protein network was less interconnected, showing coarse-stranded and bicontinuous gels, respectively. At TG > 0.03 g/L, stable W/W emulsions were formed, revealing an abrupt decrease in gel firmness, a significant loss of fracture capacity, and a decrease in the water holding capacity. These findings may be used as a starting point for the application of these gelled systems as thickeners, texture modifiers, and coating materials for delivery of bioactive compounds.Fil: Ingrassia, Romina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario; Argentina. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas; Argentina. Universidad Nacional de Rosario. Facultad de Ciencias Veterinarias; ArgentinaFil: Bea, Lucas Leonardo. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas; ArgentinaFil: Hidalgo, María Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario; Argentina. Universidad Nacional de Rosario. Facultad de Ciencias Veterinarias; ArgentinaFil: Risso, Patricia Hilda. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario; Argentina. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas; Argentina. Universidad Nacional de Rosario. Facultad de Ciencias Veterinarias; Argentin

SOFT CAMEL MILK CHEESE EFFECTS OF COAGULANTS AND PROCESSING CONDITIONS

In recent years, camel milk (CM) has been acknowledged for several health benefits, including anti-diabetic, hypoallergic, and other effects. Accordingly, CM may provide a complementary or a healthier alternative to bovine milk (BM). This has led to increased interest in processing CM to products like cheese, yogurt, and powders to extend its shelf-life. However, CM is difficult to coagulate into hard gels, affecting its cheese quality and consumer preference. The current research aimed to investigate the impact of different coagulants (chymosin, Withania coagulans, citric and acetic acid) on CM cheese quality and sensory attributes compared to BM cheese. It also evaluated the effect of pasteurization temperatures (low-temperature long-time (LTLT) and high-temperature short-time (HTST) and high-pressure processing conditions (HPP, 350, 450, and 550 MPa) on the physical, chemical, and softness properties of CM cheese in comparison to BM cheese. Large variations were found between CM and BM milk concerning coagulation time, properties, and the microstructure of the cheeses. CM cheeses were observed to have smooth and continuous casein networks, thinner aggregate strands, and smaller pore spaces, as shown by scanning electron microscope (SEM). One important finding is that CM possesses higher proteolytic activities than BM, as demonstrated by SDS-PAGE protein/peptide analysis, which might contribute to the softness of its cheese. It was also found that HTST (75°C for the 30s) negatively affected the coagulation, especially of CM, while LTLT (65°C for 30 min) provided higher quality cheeses. HHP (450 to 550 MPa for 5 min) treatments resulted in soft cheese, while HPP (350 MPa) provided better cheese quality than HTST. Thus, HPP at low pressure may offer an alternative to conventional heat treatments in providing harder camel cheese. In conclusion, the selection of coagulants and processing conditions can be tailored to improve camel cheese quality, which opens new research avenues in this field

Applications of Confocal Laser Scanning Microscopy (CLSM) in Foods

Much of the work in the area of physical properties of fats is aimed at determining the relationship among triglyceride structure, crystal properties, crystallization conditions, and macroscopic properties of fats. In finished product containing fat, some of these many macroscopic properties include spredability of margarine, butter and spreads; snap of chocolate; blooming of chocolate; and graininess, smoothness, mouthfeel, water binding, and emulsion stability of spreads [1]. Plastic fats consist of a crystal network in a continuous oil matrix. Many articles in the past have been focused on establishing relationships between lipid composition or polymorphism and macroscopic properties of fats without much consideration of the microstructure of the fat crystal network. Germane to a thorough understanding of plastic fat rheology is a characterization of its microstructure. Not including microstructure as a variable will lead to failure in the prediction of macroscopic properties. In many other non fat or low fat products macroscopic properties depend on their structural organization. Emulsion stability, which is one of the most important physical properties of multiple-phase systems, is strongly determined by oil droplet size and interactions among components that determine spatial distribution of lipid and aqueous phases. Thus, control of food properties for various applications requires a better understanding of the relationships between the food microstructure and macroscopic properties.Fil: Rincón Cardona, Jaime A.. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria; Argentina. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología; ArgentinaFil: Huck Iriart, Cristián. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Herrera, Maria Lidia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentin

Investigating the impact of exopolysaccharides on yogurt network mechanics and syneresis through quantitative microstructural analysis

Exopolysaccharides produced by lactic acid bacteria are widely used to improve the sensory properties of yogurt. The relation between the physical properties of the microbial exopolysaccharides and the structural and rheological properties of the yogurt are incompletely understood to date. To address this knowledge gap, we studied how two distinct exopolysaccharides influence the microstructure, rheological properties, and syneresis of yogurt. The effect of a negatively charged, capsular exopolysaccharide produced by Streptococcus thermophilus and a neutral, non-capsular exopolysaccharide produced by Lactococcus lactis were investigated. Using quantitative microstructural analysis, we examined yogurt samples prepared with either the capsular or the non-capsular exopolysaccharide, and with mixtures of the two. Confocal laser scanning microscopy and stimulated emission depletion microscopy were employed to visualize the microstructures, revealing differences in pore size distribution, protein domain size, and casein interconnectivity that were not apparent through visual inspection alone. Additionally, variations in rheological properties were observed among the different yogurt types. In the yogurt fermented with both bacterial strains, we observed a combined impact of the two exopolysaccharide types on relevant microstructural and rheological properties. The negatively charged capsular exopolysaccharide enhanced casein interconnectivity and gel stiffness, while the neutral non-capsular exopolysaccharide led to thicker protein domains, an abundance of small pores, and a lower loss tangent. These factors collectively hindered syneresis, resulting in improved structural integrity. Our study not only provides valuable insights into the influence of different exopolysaccharides on yogurt properties, but also presents the first demonstration and quantification of the effect of multiple types of exopolysaccharides on casein interconnectivity. These findings offer guidance for the production of yogurts with customized microstructure, rheological properties, and resistance to syneresis.<br/