R.L. Cunha

Development of probiotic dairy beverages: Rheological properties and application of mathematical models in sensory evaluation

Strawberry-flavored probiotic dairy beverages (2% vol/vol Lactobacillus acidophilus) were produced using 0, 20, 35, 50, 65, and 80% (vol/vol) whey in their formulations. Mathematical models (survival analysis, minimal significant difference, and mean global acceptance) were used to identify the optimal (sensorially) whey concentration in probiotic beverages. Fifty-five consumers evaluated acceptance of the beverages using hybrid 9-point hedonic scales. In addition, Lb. acidophilus were enumerated and pH was determined. Rheological behavior is an important characteristic for the processing and sensory acceptance of dairy beverages, varying with the presence of additives, fermentation process (time, bacterial strain), and whey concentrations used. All beverages presented minimal counts of 8 log cfu/mL of Lb. acidophilus, and pH ranged from 4.09 to 4.14. Increasing the whey content increased the fragility of the gel structure, probably because of the replacement of casein by whey proteins, once the concentrations of other ingredients in formulation were fixed. Whey content had a significant effect on acceptance of the probiotic dairy beverages; beverages with whey contents greater than 65% resulted in lower acceptance by consumers. The model of mean global acceptance presented 2 solutions with high sensory scores: beverages with 12 and 65% whey, the latter being of interest because it allows greater use of the whey by-product. The Weibull distribution presented a prediction of whey concentration of 49%, with higher sensory acceptance. The methodologies used in this research were shown to be useful in determining the constituents of food formulations, especially for whey-based probiotic beverages.

Effect of incorporation of antioxidants on the chemical, rheological, and sensory properties of probiotic petit suisse cheese

This work investigated the effect of the addition of different antioxidants (ascorbic acid, glucose oxidase, cysteine, and jabuticaba extract) on the rheological and sensorial properties of the probiotic petit suisse cheese. Absence of influence of the antioxidants at the physico-chemical characteristics of the petit suisse cheese was observed. Overall, the petit suisse cheeses presented weak gel characteristics and behaved as pseudoplastic material, except for control. All treatments exhibited a thixotropic non-Newtonian behavior; however, higher hysteresis area was obtained for control sample, which indicates that antioxidants incorporated to petit suisse had a protective effect on the typical thixotropic behavior of the Quark gel. The commercial sample presented higher scores for all aspects by consumers, whereas the probiotic petit suisse samples presented opposite behavior. Projective mapping was able to generate a vocabulary where the sample containing jabuticaba skin extract obtained by supercritical extraction was characterized by the panelists as presenting grape flavor and purple color.

Cross-linking proteins by laccase: Effects on the droplet size and rheology of emulsions stabilized by sodium caseinate

The aim of this work was to evaluate the influence of laccase and ferulic acid on the characteristics of oil-in-water emulsions stabilized by sodium caseinate at different pH (3, 5 and 7). Emulsions were prepared by high pressure homogenization of soybean oil with sodium caseinate solution containing varied concentrations of laccase (0, 1 and 5mg/mL) and ferulic acid (5 and 10mM). Laccase treatment and pH exerted a strong influence on the properties with a consequent effect on stability, structure and rheology of emulsions stabilized by Na-caseinate. At pH7, O/W emulsions were kinetically stable due to the negative protein charge which enabled electrostatic repulsion between oil droplets resulting in an emulsion with small droplet size, low viscosity, pseudoplasticity and viscoelastic properties. The laccase treatment led to emulsions showing shear-thinning behavior as a result of a more structured system. O/W emulsions at pH5 and 3 showed phase separation due to the proximity to protein pI, but the laccase treatment improved their stability of emulsions especially at pH3. At pH3, the addition of ferulic acid and laccase produced emulsions with larger droplet size but with narrower droplet size distribution, increased viscosity, pseudoplasticity and viscoelastic properties (gel-like behavior). Comparing laccase treatments, the combined addition of laccase and ferulic acid generally produced emulsions with lower stability (pH5), larger droplet size (pH3, 5 and 7) and higher pseudoplasticity (pH5 and 7) than emulsion with only ferulic acid. The results suggested that the cross-linking of proteins by laccase and ferulic acid improved protein emulsifying properties by changing functional mechanisms of the protein on emulsion structure and rheology, showing that sodium caseinate can be successfully used in acid products when treated with laccase.