Diego K. Yamul

Properties of gels from whey protein concentrate and honey at different pHs

Abstract Structural and functional properties of heat-induced gels from whey protein concentrate (WPC)-honey prepared at pHs 3.75, 4.2 and 7.0 were analyzed. Gel structure was observed by scanning electron microscopy, and the apparent transition temperature for protein denaturation was determined by differential scanning calorimetry. The solubility of the protein components in different extraction media, and the water-holding capacity, firmness, elasticity, relaxation time, adhesivity, cohesiveness and color of gels were determined. Results show that disulfide interchange reactions are important in determining the elasticity, water-holding capacity, relaxation time and cohesiveness of WPC gels. Honey decreases the relaxation time of gels prepared at pHs 7.0 and 4.2, and increases the browning and the water-holding capacity of gels, the apparent transition temperature of WPC dispersions at the three pHs assayed, and the adhesivity of acidic gels. The solubility of the protein constituents of gels in a pH 8.0 buffer increases slightly at honey concentrations of 27.5% or more, which correlates with a decrease in the gel cohesiveness, having these gels a structure with smaller pores. The products obtained could be utilized in the formulation of different desserts, such as flans and cake and tart fillings.

Physicochemical parameters and sensory properties of honeys from Buenos Aires region

The physicochemical parameters (moisture, hydroxymethyl furfural, colour, electrical conductivity, free acidity, glucose, fructose and sucrose) and the sensory properties(aroma, taste, appeareance, texture) were determined in honeys from apiaries of the agricultural, hills and meadow zones of the south east region of Buenos Aires province (Argentina). The analysis of variance showed significant differences among zones in the mean value of hydroximethyl furfural, colour, electrical conductivity and sucrose content. The principal component analysis explained the 70% of the variance among samples with the first two principal components in both cases. The cluster analysis and linear discriminant analysis showed that samples were grouped in relation to the sampling region coinciding with the results of the principal component analysis. Results suggest that could be possible to classify honeys according to the geographic origin based on the physicochemical parameters; however, the sensory properties were not good predictors.

Structure and Functionality of Whey Protein Concentrate-Based Products with Different Water Contents

Properties of different heated mixtures of whey protein concentrate, starch, gelatin, and sucrose with different water contents were studied. The water activity of samples was determined. The structural properties were analyzed by confocal laser scanning microscopy, solubility assays in different extraction solutions, polyacrylamide gel electrophoresis, and differential scanning calorimetry. Color, texture, and water-holding capacity of samples were also determined. Results show that a certain water content it is needed to form a structure with solid characteristics in these mixtures. The temperature for starch gelatinization is lower than the temperature for whey proteins denaturation, but when sucrose is present, whey proteins are denatured, before the gelatinization of starch. Sucrose is major contributor to the adhesiveness of the samples and to the decrease of their water activity. Also, sucrose decreases the firmness and cohesiveness of the samples. The main component that contributes to the browning of the samples during the heat treatment is whey protein concentrate, whereas starch is the main component responsible for the water-holding capacity in these samples. Gelatin does not modify appreciably the properties of the mixtures in the proportion used in these assays.

Influence of Milk, Corn Starch, and Baking Conditions on the Starch Digestibility, Gelatinization, and Fracture Stress of Biscuits

ABSTRACT Dough for nontraditional semisweet biscuits—prepared with wheat flour or replacing part of the wheat flour with corn starch, with or without skim milk—was baked at two oven temperatures, 120 or 170°C, until reaching moisture content and water activity lower than 6% and 0.5, respectively. Assays of fracture stress, differential scanning calorimetry, X-ray diffraction, and starch digestibility were performed. Results showed that biscuits containing milk had the highest fracture stress, and biscuits baked at low temperature were harder than biscuits baked at high temperature. The degree of starch gelatinization during baking was higher when dough was baked at 170°C, compared with dough baked at 120°C. The decrease in gelatinization coincides with the decrease in the height and surface of peaks at 15 and 23° in the X-ray diffraction patterns. Milk and corn starch did not affect the starch digestibility of biscuits, but biscuits baked at 170°C presented lower fracture stress and higher starch digestib...

A comparative study of texture and rheology of Argentinian honeys from two regions

The rheological and textural properties of 26 eastern Argentinian honeys from two different regions (North and Central) were investigated. The viscosity curves of the samples were obtained using a rotational rheometer over a temperature range of 10 to 50C. The viscosity decreased with temperature and all honeys showed a Newtonian behavior. The temperature dependence of viscosity was described using the Arrhenius, Williams-Landel-Ferry, Vogel-Taumman-Fulcher, and Power Law models. The glass transition temperatures of honeys were measured with differential scanning calorimetry and values ranged from -42.63 to -47.71C. The glass transition temperature was also predicted with the Williams-Landel-Ferry model and no significant differences were observed with the experimental results. Rheological parameters were obtained by small amplitude oscillation experiments. Results indicated that the viscous modulus was higher than the storage modulus within all the frequency ranges assayed and honeys from the North region were more viscous. Results of the back extrusion test showed that honeys from the Central region are harder and both groups of honeys (North and Central) exhibited the same consistency and adhesivity. PRACTICAL APPLICATIONS The honey chain production starts with the extraction of the product from the combs, pumping it through pipes and finishes at the packaging of the product. During all these stages, honey viscosity is a key parameter to ensure proper processing and quality control, preventing the waste of economic resources. Determining honey viscosity is of great importance for the industry to select the equipment such as pumps, mixers, filters, centrifuges, heat exchangers, and optimization of industrial processes. The rheological and textural properties of honey are very important in terms of applications related to quality control and authenticity of honeys. Honey authenticity increases the trust of consumers to certified food products. Argentina is one of the leading honey producers and exporters in the world, but information on the rheological, thermal, and textural characteristics of Argentinian honey is very poor in the scientific literature.

Obtention and characterization of dried gels prepared with whey proteins, honey and hydrocolloids mixture: Development and characterization of a whey protein-honey-hydrocolloid snack

BACKGROUND Large amounts of honey and liquid whey derived from the dairy industry are produced in Argentina. Honey is exported in bulk and whey is transformed into whey protein concentrates and isolates. The objective of this work was to investigate the effect of pH, composition and storage time on the properties of dried gels with honey, whey proteins and hydrocolloids. RESULTS Color properties varied according to pH and composition. The fracture stress of dried gels prepared with corn starch was higher than that of gels prepared with guar gum in all conditions assayed. Youngs modulus was higher at pH 7 for both compositions and increased with storage time. Rubbery characteristics were found in dried gels with guar gum, while both corn starch and guar gum made the microstructure rougher. Multivariate analysis showed that samples could be grouped by pH. Panelists preferred pH 7 products over acidic ones, and no significant differences in sensory properties were found using either corn starch or guar gum in the formulation. CONCLUSION The results demonstrated that it is possible to generate a new product, which may open new applications for honey and whey in food formulations.