Alicia Califano

Partial least squares correlations between sensory and instrumental measurements of flavor and texture for Reggianito grating cheese

Abstract Visual, manual and oral texture descriptors for Reggianito grating cheese were correlated with parameters obtained from an instrumental compression test. Aroma and flavor descriptors were correlated with organic acid concentrations. Linear partial least squares regression was used for the multivariate correlations and proved to be a useful tool. Measurements were done between 30 and 290 days of ripening time. Strain at breaking point was the instrumental texture parameter which best correlated with sensory descriptors: negatively wth visual, manual and oral fracturability; and positively with manual elasticity. Sensory hardness was related to instrumental hardness although the correlation coefficients were not high. Total flavor and aroma intensity were well correlated with propionic acid, suggesting this acid could be a flavor indicator for this type of cheese. Uric and orotic acids changed during ripening yet remained below sensory threshold values.

Low-fat meat sausages with fish oil: optimization of milk proteins and carrageenan contents using response surface methodology.

Response surface methodology was used to analyze the effect of milk proteins and 2:1 κ:ι-carrageenans on cooking loss (CL), weight lost by centrifugation (WLC) and texture attributes of low-fat meat sausages with pre-emulsified fish oil. A central-composite design was used to develop models for the objective responses. Changes in carrageenans affected more the responses than milk proteins levels. Convenience functions were calculated for CL, WLC, hardness, and springiness of the product. Responses were optimized simultaneously minimizing CL and WLC; ranges for hardness and springiness corresponded to commercial products (20 g of pork fat/100 g). The optimum corresponded to 0.593 g of carrageenans/100 g and 0.320 g of milk proteins and its total lipid content was 6.3 g/100 g. This formulation was prepared and evaluated showing a good agreement between predicted and experimental responses. These additives could produce low-fat meat sausages with pre-emulsified fish oil with good nutritional quality and similar characteristics than traditional ones.

Mechanical and optical characterization of gelled matrices during storage.

The effect of composition and storage time on the rheological and optical attributes of multi-component gels containing locust bean gum (LBG), low acyl (LAG) and high acyl (HAG) gellan gums, was determined using three-component mixture design. The generalized Maxwell model was used to fit experimental rheological data. Mechanical and relaxation spectra of gelled systems were determined by the type of gellan gum used, except LBG alone which behaved as a diluted gum dispersion. Storage time dependence of the gels was analyzed using the rubber elasticity theory and to determine changes in network mesh size the equivalent network approach was applied. Destabilization kinetic was obtained from light scattering results; increasing LAG content improved the long-term stability of the matrices. Almost every formulation exhibited an increment in both moduli during the first 10 days remaining practically constant thereafter or until they broke (binary mixtures with LBG); gels with HAG/LBG mixtures were the least stable.

Weight loss prediction during meat chilling

A lumped parameter model for computing weight losses during meat chilling is proposed. The model is independent of the shape of the piece of meat and allows the fraction of fat and bone to be taken into account. With this information a distinction between the heat transfer and the mass transfer areas can be established. Also provided is a correction factor which permits the existence of temperature gradients inside the meat to be taken into consideration. With the aid of the model the effect of the different operating variables on weight losses is analysed. The values predicted by the model show good agreement with experimental data obtained by other authors for the chilling of steers, cows and lambs under a wide range of operating conditions.

Partial dehydration and cryopreservation of Citrus seeds

BACKGROUND Three categories of seed storage behavior are generally recognized among plant species: orthodox, intermediate and recalcitrant. Intermediate seeds cannot be stored in liquid nitrogen (LN) without a previous partial dehydration process. The water content (WC) of the seeds at the moment of immersion in LN must be regarded as the most critical factor in cryopreservation. The purpose of this study was to investigate the basis of the optimal hydration status for cryopreservation of Citrus seeds: C. sinensis (sweet orange), C. paradisi (grapefruit), C. reticulata (mandarin) in LN. RESULTS To study the tolerance to dehydration and LN exposure, seeds were desiccated by equilibration at relative humidities between 11 and 95%. Sorption isotherms were determined and modeled; lipid content of the seeds was measured. Seed desiccation sensitivity was quantified by the quantal response model. Differential scanning calorimetry (DSC) thermograms were determined on cotyledon tissue at different moisture contents to measure ice melting enthalpies and unfrozen WC. Samples of total seed lipid extract were also analyzed by DSC to identify lipid transitions in the thermograms. CONCLUSIONS The limit of hydration for LN Citrus seeds treatment corresponded to the unfrozen WC in the tissue, confirming that seed survival strictly depended on avoidance of intracellular ice formation.

Food Gel Emulsions: Structural Characteristics and Viscoelastic Behavior

If the continuous phase of an emulsion or foam is a semisolid system, these systems can be described as ‘filled gels’ or ‘composite solids’. Gel emulsions are widely used in different industries like cosmetic, pharmaceutical, and food, among others. Typical examples are cheese, many desserts, sausages, low-fat mayonnaises and bakery products. The aggregation and cross-linking of protein and polysaccharides molecules into three-dimensional solid-like networks (‘gels’) is one of the most important mechanisms for developing microstructure with desirable textural attributes. Due to their elastic characteristics, oil droplets can be kept in suspension avoiding creaming. The structure and the rheological properties of gel emulsions are dependent on the nature of the interactions between the emulsifiers adsorbed on the surface of the droplets that fill the emulsion and the biopolymeric network formed in the aqueous phase. The present chapter deals with the viscoelastic behavior of o/w gel emulsions containing either polysaccharides or proteins in the aqueous phase. Two case studies are discussed, i.e., emulsions with low lipid content, stabilized with bovine gelatin of different molecular weights and heat-induced gel emulsions containing high acyl gellan gum. Small amplitude oscillatory shear tests (stress and frequency sweeps) and transient studies (creep-recovery) were performed over the different matrices and modeled to interpret the structural characteristics of the gel emulsions. The Broadened Baumgaertel-Schausberger-Winter spectrum was used to represent the linear viscoelastic behavior of the continuous phase and the emulsified system. Relaxation spectra were validated using creep experiments.

Food grade microemulsion systems: Sunflower oil/castor oil derivative-ethanol/water. Rheological and physicochemical analysis

Microemulsions are thermodynamically stable systems that have attracted considerable attention in the food industry as delivery systems for many hydrophobic nutrients. These spontaneous systems are highly dependent on ingredients and composition. In this work phase diagrams were constructed using two surfactants (Kolliphor RH40 and ELP), water, sunflower oil, and ethanol as cosurfactant, evaluating their physicochemical properties. Stability of the systems was studied at 25 and 60 °C, monitoring turbidity at 550 nm for over a month to identify the microemulsion region. Conductivity was measured to classify between water-in-oil and oil-in-water microemulsions. The phase diagram constructed with Kolliphor RH40 exhibited a larger microemulsion area than that formulated with Kolliphor ELP. All formulations showed a monomodal droplet size distribution with low polydispersity index (<0.30) and a mean droplet size below 20 nm. Systems with higher water content presented a Newtonian behavior; increasing the dispersed phase content produced a weak gel-like structure with pseudoplastic behavior under flow conditions that was satisfactorily modeled to obtain structural parameters.

Response Surface Methodology to Assay the Effect of the Addition of Proteins and Hydrocolloids on the Water Mobility of Gluten-Free Pasta Formulations

In gluten-free pasta formulation (suitable for those suffering from celiac disease), the influence of each constituent has a major importance on the final product quality, especially water and hydrocolloid contents used to replace the gluten matrix. Gluten-free doughs are mixed dispersed systems; the dispersion medium contains several types of dispersed particles, with two main construction materials—polysaccharides and proteins. Four levels of structural hierarchy in dispersed food systems can be distinguished: submolecular, molecular, supermolecular, and macroscopic. Structural functions of a biopolymer depend upon its place in the structural hierarchy of the product (Tolstoguzov 2000).