Enrique Palou

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

IMPREGNATION AND OSMOTIC DEHYDRATION OF SOME FRUITS: EFFECT OF THE VACUUM PRESSURE AND SYRUP CONCENTRATION

Apple, mango and melon were subjected to impregnation and osmotic dehydration at vacuum pressure (VI-VOD). The effect of the vacuum pressure (135–674 mbar) and concentration of the sucrose solutions (41–60°Brix) on the mass transfer parameters were evaluated. The lowest final aw levels in apple and mango were achieved with 50°Brix syrup and vacuum pressure of 674 mbar and in melon with 57°Brix and 593 mbar. Water loss of similar magnitude was observed in melon and mango, and there was water gain in the case of apple. The solids gain (SG) in apple was higher than in melon and mango. Minimal values of SG were detected in mango, and a maximum SG value was observed in apple. Melon and mango presented weight losses of up to 8.9% while the weight of apple increased. Results indicated that the impregnation phenomena predominated in the combined VI-VOD process of apple and osmotic dehydration phenomena in melon and mango.

Antifungal activity by vapor contact of essential oils added to amaranth, chitosan, or starch edible films

Antimicrobial agents can be incorporated into edible films to provide microbiological stability, since films can be used as carriers of a variety of additives to extend product shelf life and reduce the risk of microbial growth on food surfaces. Addition of antimicrobial agents to edible films offers advantages such as the use of small antimicrobial concentrations and low diffusion rates. The aim of this study was to evaluate inhibition by vapor contact of Aspergillus niger and Penicillium digitatum by selected concentrations of Mexican oregano (Lippia berlandieri Schauer), cinnamon (Cinnamomum verum) or lemongrass (Cymbopogon citratus) essential oils (EOs) added to amaranth, chitosan, or starch edible films. Essential oils were characterized by gas chromatography-mass spectrometry (GC/MS) analysis. Amaranth, chitosan and starch edible films were formulated with essential oil concentrations of 0.00, 0.25, 0.50, 0.75, 1.00, 2.00, or 4.00%. Antifungal activity was evaluated by determining the mold radial growth on agar media inoculated with A. niger and P. digitatum after exposure to vapors arising from essential oils added to amaranth, chitosan or starch films using the inverted lid technique. The modified Gompertz model adequately described mold growth curves (mean coefficient of determination 0.991 ± 0.05). Chitosan films exhibited better antifungal effectiveness (inhibition of A. niger with 0.25% of Mexican oregano and cinnamon EO; inhibition of P. digitatum with 0.50% EOs) than amaranth films (2.00 and 4.00% of cinnamon and Mexican oregano EO were needed to inhibit the studied molds, respectively). For chitosan and amaranth films a significant increase (p<0.05) of lag phase was observed among film concentrations while a significant decrease (p<0.05) of maximum specific growth was determined. Chitosan edible films incorporating Mexican oregano or cinnamon essential oil could improve the quality of foods by the action of the volatile compounds on surface growth of molds.

Impregnation properties of some fruits at vacuum pressure

Abstract The effects of vacuum pressure and its application time on the volume of isotonic solution (IS) impregnated in slices of mango, apple, papaya, banana, peach, melon, and mamey were studied using response surface methodology. Fruits were subjected to vacuum impregnation (VI) treatments using sucrose IS. VI times between 3 and 45 min and vacuum pressures (VP) between 135 and 674 mbar were applied. Second order polynomials were developed to estimate the volume of IS impregnated in each fruit (R2⩾0.870). VP had a significant effect (p⩽0.10) on the volume of IS impregnated in fruit slices of all the studied fruits. The impregnation also depended significantly (p⩽0.10) on the VI time, except for apple. Under the studied conditions, the effective porosity values of the fruits varied from 0.016 for mamey to 0.330 for apple.

Susceptibility of food-borne bacteria to binary combinations of antimicrobials at selected aw and pH

Aim:  To evaluate the antibacterial susceptibilities of food‐borne bacteria to individual and binary mixtures of a synthetic antimicrobial agent with a natural phenolic compound.

High pressure-processed guacamole

Abstract The effects of continuous or oscillatory high pressure (HP) treatments on polyphenoloxidase (PPO) and lipoxygenase (LOX) activities, standard plate, yeast and mold counts, sensory acceptability, and instrumental color in guacamole were evaluated. Significantly less ( P P >0.05) from that of guacamole controls. Browning during storage was related mainly to changes in the hue attributed to a decrease in the green contribution to the color.

Bactericidal Action of Binary and Ternary Mixtures of Carvacrol, Thymol, and Eugenol against Listeria innocua

The bactericidal effect of 3 natural agents (carvacrol, thymol, and eugenol) was evaluated as well as their binary and ternary mixtures on Listeria innocua inactivation in liquid model systems. Minimal bactericidal concentrations (MBC) of these agents were determined, and then binary and ternary mixtures were evaluated. Culture media were inoculated with L. innocua and incubated for 72 h at 35 °C. Turbidity of studied systems were determined every 24 h. The most effective individual antimicrobial agent was carvacrol, followed by thymol and then eugenol with MBCs of 150, 250, and 450 mg kg(-1), respectively. It was observed that the most effective binary mixture was 75 mg kg(-1) carvacrol and 62.5 mg kg(-1) thymol. Furthermore, the ternary mixture carvacrol-thymol-eugenol in concentrations of 75, 31.25, and 56.25 mg kg(-1), correspondingly, was the most effective for L. innocua inactivation. Several binary and ternary mixtures of these 3 natural antimicrobial agents worked adequately to inactivate L. innocua.

Aspergillus flavus dose–response curves to selected natural and synthetic antimicrobials

The effects of selected concentrations of antimicrobials from natural (vanillin, thymol, eugenol, carvacrol or citral) or synthetic (potassium sorbate or sodium benzoate) origin on Aspergillus flavus lag time inoculated in laboratory media formulated at water activity (a(w)) 0.99 and pH 4.5 or 3.5, were evaluated. Time to detect a colony with a diameter > 0.5 mm was determined. Mold response was modeled using the Fermi function. Antimicrobial minimal inhibitory concentration (MIC) was defined as the minimal required inhibiting mold growth for 2 months. Fermi function successfully captured A. flavus dose-response curves to the tested antimicrobials with a highly satisfactory fit. Fermi equation coefficients, Pc and k, were used to compare antimicrobials and assess the effect of pH. Important differences in Pc and k were observed among antimicrobials, being natural antimicrobials less pH dependent than synthetic antimicrobials. A large Pc value represents a small antimicrobial effect on A. flavus lag time; thus, high concentrations are needed to delay growth. A. flavus exhibited higher sensitivity to thymol, eugenol, carvacrol, potassium sorbate (at pH 3.5), and sodium benzoate (at pH 3.5) than to vanillin or citral. MICs varied from 200 ppm of sodium bcnzoate at pH 3.5 to 1800 ppm of citral at both evaluated pHs.

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.

Effect of oscillatory high hydrostatic pressure treatments on Byssochlamys nivea ascospores suspended in fruit juice concentrates

The effect of continuous (689 MPa with holding times of 5, 15 or 25 min) and oscillatory (one, three or five cycles at 689 MPa with holding times of 1 s) high hydrostatic pressure treatments on the viability of Byssochlamys nivea ascospores suspended in apple and cranberry juice concentrates adjusted by dilution to water activities (aw) of 0·98 and 0·94 was evaluated at 21 and 60 °C. Inactivation of the initial spore inocula was achieved after three or five cycles of oscillatory pressurization at 60 °C when the aw was 0·98 in both fruit juices. With aw 0·94, the initial inocula were reduced by less than 1 log‐cycle after five pressure cycles. Inactivation was not observed within 25 min with continuous pressurization at 60 °C. In treatments at 21 °C, no effect on spore viability was observed with continuous or oscillatory treatments.