The objective of this work is to prepare biodegradable films of corn starch, replacing a part of the distilled water used in the formulation of the filmogenic solution with an aqueous extract of Hibiscus sabdariffa L. (HSE) and evaluate its functional properties and antimicrobial capacity. The films are made by casting method, adding different HSE:water volume ratios: 100:0, 75:25, 50:50, 25:75, and 0:100 as control. All films with HSE showed an antimicrobial effect, giving positive results against Listeria monocytogenes, Staphylococcus aureus, Salmonella spp., and Escherichia coli. It is observed that, with the increase in the proportion of HSE, the films are more manageable and glossy than those of starch alone and a more intense red color as the extract content increased, significantly improving its mechanical properties, mainly when the HSE content is above 25% on the filmogenic solution. Likewise, the addition of the extract significantly improved the water vapor barrier capacity of the films. According to the results obtained in this study, corn starch films with aqueous extract of H. sabdariffa are an excellent alternative as a biodegradable packaging material for the food industry, with good functional properties and antimicrobial capacity.
Pulque is a typical fermented alcoholic beverage of central Mexico, produced from the nectar of maguey agave plants. Production systems are largely artisanal, with inadequate hygiene conditions and exposure to multiple contamination sources. No data exist on pulque microbiological safety and the behavior of pathogenic microorganisms in agave nectar and pulque. An initial trial was done of the behavior of Salmonella Typhimurium, Staphylococcus aureus, Listeria monocytogenes, and Shigella flexneri and Shigella sonnei during fermentation of nectar from a single producer, nectar mixture from different producers, and seed pulque. A second trial simulating artisanal pulque production was done by contaminating fresh nectar with each of the five strains, storing at 22°C for 14 h, adding seed pulque, and fermenting until pulque was formed. During incubation at 16 or 22°C in the first trial, all the pathogenic strains multiplied in both the single producer nectar and the nectar mixture, reaching maximum concentrations at 12 h. Strains concentration then decreased slowly. In the seed pulque, the strains did not multiply and tended to die. In the second trial, all strains increased concentration from 0.7 to 1.6 log at 22°C, and from 0.5 to 1.1 at 16°C in the first 14 h. After addition of seed pulque, they were quickly deactivated until none was detected in the final product. The results suggest that the potential risk to consumers of contracting any of the five tested pathogenic bacterial strains from pulque is low.
Packaging materials play an essential role in the preservation and marketing of food and other products. To improve their conservation capacity, antimicrobial agents that inhibit bacterial growth are used. Biopolymers such as starch and chitosan are a sustainable alternative for the generation of films for packaging that can also serve as a support for preservatives and antimicrobial agents. These substances can replace packaging of synthetic origin and maintain good functional properties to ensure the quality of food products. Films based on a mixture of corn starch and chitosan were developed by the casting method and the effect of incorporating cellulose nanocrystals (CNC) at different concentrations (0 to 10% w/w) was studied. The effect of the incorporation of CNC on the rheological, mechanical, thermal and barrier properties, as well as the antimicrobial activity of nanocomposite films, was evaluated. A significant modification of the functional and antimicrobial properties of the starch–chitosan films was observed with an increase in the concentration of nanomaterials. The films with CNC in a range of 0.5 to 5% presented the best performance. In line with the physicochemical characteristics which are desired in antimicrobial materials, this study can serve as a guide for the development this type of packaging for food use.
Kinetic parameters of thermal inactivation of pectin methylesterase (PME) in a partially purified mango enzyme extract were determined. The PME of mango partially purified by salting out showed different patterns of thermal inactivation, indicating the presence of a thermostable fraction at 70 °C and a thermolabile fraction at lower temperatures. The inactivation of the thermostable fraction exhibited a linear behavior that yielded a z-value of 9.44 °C and an activation energy (Ea) of 245.6 kJ mol -1 K -1 using the Arrhenius model. The thermostable mango PME fraction represented 17% of total crude enzyme extract, which emphasizes the importance of residual enzyme activity after heat treatment.
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