TOTAL AND SOLUBLE DIETARY FIBER VARIATION IN CYAMOPSIS TETRAGONOLOBA (L.) TAUB. (GUAR) GENOTYPES

The endosperm of guar seed is the source of a soluble hydrophilic polysaccharide gum that is used as an emulsifier, thickener and stabilizer in a wide range of foods and is part of the seed total dietary fiber (TDF). This study examined the content and variation in TDF and soluble dietary fiber (SDF) in seeds of guar, Cyamopsis tetragonoloba (L.) Taub., accessions with diverse morphological traits. TDF and SDF, respectively, made up 52–58% (n = 9 accessions) and 26–32% (n = 8 accessions) of seed dry weight. Both TDF and SDF displayed significant genotypic variability. The magnitude of the variability indicates the possibility of improving these traits through plant breeding. Variability of protein, lipid, ash and dry matter content of seed was also observed.     

Fat Concentration Affects Sweetness and Sensory Profiles of Sucrose, Sucralose, and Aspartame

The sensory characteristics of sucralose, aspartame, and sucrose were studied in an unflavored lipid model system varying in fat levels. One study investigated the effects of fat on the potencies (vs. sucrose) of sucralose and aspartame. We also examined absolute changes in all three sweeteners in taste, temporal, and mouthfeel properties at fiied concentrations across a wide fat range. Results indicated a modest decrease in the potencies of sucralose and aspartame across fat concentrations, especially at lower sweetness levels. All sweeteners responded similarly to changes in fat concentration. Independent of fat level, sucralose was perceived more similar to aspartame in onset, bitterness, and aftertaste, than to sucrose.     

MICROBIAL GROWTH IN PACKAGED FRESH ASPARAGUS

The effects of storage temperature and time on the microflora of fresh, vacuum packaged, and modified atmospheres packaged asparagus (Asparagus officinalis) were analyzed. Total aerobic mesophilic, psychrophilic, lactic acid bacteria, Enterobacteriaceae, and yeast and molds were determined as a function of time. The effect of washing on the original microflora of the asparagus and the growth of the different microbial groups during the storage time were checked. From day 8, a progressive increase in the mesophile and psychrophile counts in both types of packaging was observed. At the end of the experiment (day 21), the mesophile and psychrophile counts were all 10⁷ CFU/g, for both types of packaging. In the vacuum packaging, the final enterobacteria counts (2.5 × 10² CFU/g) and yeast and molds (10 CFU/g) were lower than in the polyethylene bag packaged asparagus, which showed enterobacteria counts of 7.3 × 10⁴ CFU/g) and yeast and mold counts of 2.3 × 10⁴ CFU/g. The non-packaged asparagus showed low counts from the fourth day due to their heavy dehydration caused by the low relative humidity in the storage chamber.     

Kinetics of enzymic hydrolysis of cassava flour starch — optimization and modelling

This study was conducted to model the kinetics of cassava flour hydrolysis by Miles Taka-Therm L–170 alpha amylase and Diazyme L–200 glucoamylase to produce glucose syrup. Maximum starch concentration was 33% due to a controlled process of flour gelatinization by gradual temperature increase, and parallel starch hydrolysis by thermostable alpha amylase activity, preventing excess viscosity. The time of hydrolysis was two and half hours of alpha amylase activity and 36 h of glucoamylase activity with the final yield of 90–93% of glucose. Exponential hyperbolic models were obtained to predict the kinetic of hydrolysis both amylase and glucoamylase, with a generalized correlation coefficient >0.94.     

Water activity of culture media used in food microbiology

An improved gravimetric method was used to simultaneously determine (in a single assay) the water activity ( a_w ) of 30 solid and liquid culture media covering the entire useful range of a_w in food microbiology, including media recommended for osmophilic, halophilic and xerophilic organisms. The water activities of the media ranged between 0.999 and 0.739. As could be expected, the water activities of the solid media were not affected significantly by the presence of agar. No significant differences were observed either between the gravimetric (20°C) and the cryoscopic measurements (below 0°C) of liquid media of very high a_w .     

Ascorbic acid loss and sensory changes in intermediate moisture pineapple during storage at 30–40°C

Kinetics of ascorbic acid loss as a function of storage temperature (30, 35 and 40°C) and water activity of intermediate moisture pineapple slices at a _W of 0.92, 0.95 and 0.97 was modelled. Loss was faster at higher a _W but storage temperatures of 30 - 40°C had little effect at the same a _w. Colour changes were larger than flavour changes. Spoilage was only a problem at high a _w.     

Influence of High-Pressure Treatment at 25°C and 80°C on Folates in Orange Juice and Model Media

ABSTRACT: The influence of high-pressure treatment on the 3 main folate species present in orange juice was assessed under conditions similar to those used in high-pressure pasteurization and sterilization using freshly squeezed orange juice and different model orange juices. The latter were used also to determine the influence of matrix components, pH, and excess ascorbic acid. Excess ascorbate strongly protected folates against pressure and heat. Pressurization at 600 MPa and 80°C affected model juice folates synergistically, and pressure increased the formation of 5,10-methenylfolate. In fresh orange juice, components other than ascorbate additionally stabilized folates, thus pressure preservation and pressure sterilization appeared very feasible.     

Microwave Digestion of Multi-Component Foods for Sodium Analysis by Atomic Absorption Spectrometry

Microwave digestion of a variety of low-sodium dinners was evaluated for determining sodium content. Dinners containing a meat, vegetable and dessert portion were blended, digested with strong acid in the microwave oven, and read by atomic absorption. Sodium values were compared with those obtained by an FDA method. Also, a sodium standard of known concentration was added to some samples, and the recoveries measured for two different amounts added. Reproducibility of microwave digestion was tested on replicates analyzed on the same day, on consecutive days and on consecutive weeks. Of the ten dinner types tested no matrix effects or interferences were noted, and we concluded that microwave digestion is a rapid means of preparing a complex matrix such as a frozen dinner for sodium analysis.     

Carbon supported Pt–Cr alloys as oxygen-reduction catalysts for direct methanol fuel cells

Electrocatalytic activities of various carbon-supported platinum–chromium alloy electrocatalysts towards oxygen reduction in 1 mol l⁻¹ H₂SO₄ and in 1 mol l⁻¹ H₂SO₄/1–3 mol l⁻¹ CH₃OH, were investigated by means of rotating disc electrode experiments and in solid polymer electrolyte direct methanol fuel cells. The activity of these electrocatalysts for methanol oxidation was evaluated using cyclic voltammetry. It was found that Pt₉Cr/C prepared by reduction with NaBH₄ exhibits the lowest activity for methanol oxidation and the highest activity for oxygen reduction in the presence of methanol, in comparison to commercial Pt/C, Pt₃Cr/C and PtCr/C electrocatalysts.