A. Argaiz

Effect of temperature on the moisture sorption isotherms of some cookies and corn snacks

Abstract Three cookies and two corn snacks were analyzed for major components and their moisture adsorption characteristics were evaluated at 25, 35 and 45 °C. The main composition differences were in fat and total carbohydrate content. The isotherms of each product were different (p

Effect of natural vanillin on germination time and radial growth of moulds in fruit-based agar systems

The inhibitory effects of various concentrations of natural vanillin on the growth of Aspergillus flavus, A. niger, A. ochraceus and A. parasiticus in laboratory media and five fruit (apple, banana, mango, papaya and pineapple)-based agars at pH 3·5 and water activity (a w ) 0·98 were studied. The most resistant mould to the conditions studied was A. niger , followed by A. parasiticus, A. flavus and A. ochraceus . For each mould the increase in vanillin concentration and the type of fruit used in agar preparation significantly ( P

THE USE OF PELEG'S EQUATION TO MODEL OSMOTIC CONCENTRATION OF PAPAYA

ABSTRACT A two parameter non exponential model was recently proposed by Peleg to describe moisture sorption curves. This study was designed to examine the predictive capacity of the model for osmotic concentration data and to further investigate the characteristics of the parameters in the equation. The equation was used to model the kinetics of water removal and solute uptake, in terms of moisture content (MC) and soluble solids (SS) respectively, during the osmotic concentration of papaya. The model - fitted the experimental observations accurately, with regression coefficients that varied from 0.982 to 0.997 and from 0.976 to 0.996 for MC and SS respectively, and with maximum root-mean-square deviations of 0.6 g water/100g and 0.5°Brix, for moisture content and soluble solids respectively. An inverse relationship was found between k2 parameter and syrup concentration as well with MC and SS.

Shelf-stable high moisture papaya minimally processed by combined methods

Abstract A preservation process to achieve microbial and sensorial stability of papaya slices stored at 25°C at least during five months was developed. The preservation process was based on ‘combined methods technology’, and included the combination of the following factors: a mild heat treatment (blanching), a water activity reduction, a pH decrement, and the addition of potassium sorbate and sodium bisulfite. The obtained fruit stored at 5 and 25°C during five months was evaluated for color and texture changes, sulfite and potassium sorbate degradation kinetics, changes of aerobic plate counts, yeasts and molds, ascorbic acid retention and sensorial quality changes. Moisture and soluble solids contents, pH, and water activity remained almost constant and the product obtained was microbiologically sound during storage. There was an enzymatic sucrose hydrolysis that reduced the water activity more than expected, which helps to assure the microbial stability. Total sulfite and potassium sorbate concentrations were reduced during storage at 5 and 25°C, giving final concentrations 62 and 66%, and 40 and 60% of the initial concentrations, respectively. Ascorbic acid content of papaya was reduced during processing and storage. Color, texture and sensory evaluation reveal that there were no significant differences between samples stored at 5 and 25°C. The papaya slices obtained showed a good overall acceptability (initial mean score 7·25) even after five months of storage at 25°C (final mean score 6·73)

Synergistic inhibitory effect of citral with selected phenolics against Zygosaccharomyces bailii.

Antifungal susceptibilities of Zygosaccharomyces bailii to individual and binary mixtures of citral with selected phenolics were evaluated to identify synergistic combinations. Individual effects of citral, vanillin, thymol, carvacrol, and eugenol concentrations and combined effects of citral with the other phenolic compounds on the growth of Z. bailii were evaluated in potato dextrose agar, adjusted with sucrose to a water activity of 0.99 or 0.95, and hydrochloric acid to pH 4.5 or 3.5. MICs for individual and binary antimicrobial mixtures were identified and then transformed to fractional inhibitory concentrations. Inhibitory concentrations of citral and vanillin were higher than 650 ppm, whereas for thymol, eugenol, and carvacrol, concentrations were lower than 250 ppm for several of the studied water activity-pH conditions. Combining citral with the other phenolic compounds, fractional inhibitory concentration (FIC) and FIC(Index) varied from 0.216 to 0.582. FIC(Index) demonstrated synergistic effects on Z. bailii inhibition when citral was used in combination with vanillin, thymol, carvacrol, or eugenol. Therefore, the relative amount of antimicrobials could be greatly reduced.

OSMOTIC DEHYDRATION OP PAPAYA WITH CORN SYRDP SOLIDS

Abstract The water activity (aw) lowering capacity of four corn syrup solids (CSS) with nominal dextrose equivalent (DE) values of 10, 20, 30, and 40, and the osmotic concentration kinetics of papaya with solutions (50% w/w) of these solutes were studied. Apparent molecular weights (MWa) were calculated and the awlowering capacity was characterized for each solute with Norrishs equation calculating a specific constant (K). The awlowering capacity increased as the DE value increased. Logarithmic relationships were found between the MWaand the DE value and between K and DE (r ≥ 0.993).. The predicted awvalues using the MWaand K of each CSS were in good agreement (average root mean square deviation ≤0.002) with the experimental data. Osmotic concentration was evaluated in terms of water loss (WL), loss of weight (LW) and solid gain (SG). The final values of SG increased and WL and LW decreased as the DE decreased. SG, WL and LW varied from 7.3 to 21.1% 76.1 to 49.1% and 72.0 to 28.0%, respectively for the C...