Aurelio López-Malo

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 ultrasound on the survival of Saccharomyces cerevisiae: influence of temperature, pH and amplitude

The resistance of Saccharomyces cerevisiae cells to the action of ultrasound (20 kHz, wave amplitude in the range 71–110 μm) was analyzed at 35, 45 and 55°C in Sabouraud broth at pH 3.0 and 5.6. The inactivation rate where a first-order kinetic was observed exhibited D values between 0.5 and 31 min. The resistance of the yeast decreased as ultrasonic wave amplitude increased, with the z values for this effect ranging between 128 and 323 μm. In the pH range investigated, the reduction of pH did not affect ultrasound yeast sensitivity except for experiments performed at 71.4 μm wave amplitude and 45°C. At moderate temperatures, decimal reduction time values were reduced by the simultaneous effect of ultrasound but at 55°C, no advantages were observed by adding sonication. Structural studies performed in cells sonicated at 45°C and 95.2 μm of wave amplitude indicated the treatment provoked puncturing of cell walls with leakage of content as well as damage at subcellular level. However, when ultrasound was applied at 55°C, no structural differences were appreciated between sonicated cells and only heat-treated cells.

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.

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

Recent Studies Related to Microwave Processing of Fluid Foods

Microwave heating is a convenient way to heat materials; it is considered to be a fast, clean, and easy to use technology. The use of microwaves for industrial food unit operations is the subject of research since several years ago. However, the application of microwaves depends, among other variables, on the dielectric properties of the material to be heated; otherwise, the efficiency of the process and the quality of the final product cannot be guaranteed. This paper reviews basic concepts related to microwaves and dielectric properties, and then it presents reported dielectric properties data for selected fluid foods and microwave-heating processes that have been recently studied. These processes are focused mainly on microbial inactivation, enzyme inactivation, chemical, physical, or sensory changes evaluation, or for reheating. The temperature uniformity is also discussed as a key issue for successful application of microwave heating, which is now applied by some companies.

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.