Combined effect of gamma irradiation,ascorbic acid,and edible coating on the improvement of microbial and biochemical characteristics of ground beef

This study was conducted to evaluate the combined effect of gamma irradiation and the incorporation of natural antimicrobial compounds in cross-linked films on the microbiological and biochemical characteristics of ground beef. Medium-fat (23% fat) ground beef patties were divided into three separate treatment groups: (i) control samples without additives, (ii) ground beef samples containing 0.5% (wt/wt) ascorbic acid, and (iii) ground beef samples containing 0.5% ascorbic acid and coated with a protein-based cross-linked film containing immobilized spice powders. Meat samples were irradiated at doses of 0, 1, 2, and 3 kGy and stored at 4 +/- 2 degrees C. Microbial growth (based on total aerobic plate counts [APCs] and total coliforms) was evaluated, as were the content of thiobarbituric acid-reactive substances (TBARS) and that of free sulfydryl groups. At the end of the storage period, Enterobacteriaceae, presumptive Staphylococcus aureus, presumptive Pseudomonas spp., Brochothrix thermosphacta, and lactic acid bacteria were enumerated. Regardless of the treatment group, irradiation significantly (P < or = 0.05) reduced the APCs. Irradiation doses of 1, 2, and 3 kGy produced immediate APC reductions of 2, 3, and 4 log units, respectively. An APC level of 6 log CFU/g was reached after 4, 7, and 10 days for samples irradiated at 1, 2, and 3 kGy, respectively. Lactic acid bacteria and B. thermosphacta were more resistant to irradiation than were Enterobacteriaceae and Pseudomonas. The TBARS and free sulfydryl contents were stabilized during postirradiation storage for samples containing ascorbic acid and coated with the protein-based cross-linked film containing immobilized spice powders.     

Influence of Some Fatty Acids on Oviposition by the Bruchid Beetle, Callosobruchus maculatus

The cowpea seed beetle, Callosobruchus maculatus, will lay its eggs on many potential hosts and inert surfaces. Oviposition on glass beads is stimulated by coating them with individual fatty acids. Nevertheless, female beetles reject mung seeds less frequently than beads treated with either an extract of mung seeds or, especially, an extract of mung seeds plus oleic acid. The addition of oleic acid to the extract resulted in a change in the sequence of oviposition behavior, notably an increase in a raised body position indicative of hosts of low acceptability. Fatty acids are present in the epicuticular waxes of legume seeds; wax extract of mung bean contains 32.4% fatty acid and 14 alkanes, whereas a wax extract of chickpea contains 5% fatty acid and 18 alkanes. Thus, chickpea may be a less acceptable host for oviposition than mung bean because of physical differences and/or because of chemical differences, including a reduced total level of fatty acid or the high proportion of oleic acid it is reported to contain. It is concluded that an appropriate mixture of fatty acids in the epicuticular waxes stimulates oviposition but that an elevated level of oleic acid in conjunction with others is deterrent.     

Synthesis and Characterization of a New Bifunctionalized,Fluorescent, and Amphiphilic Molecule for Recruiting SH‐Containing Molecules to Membranes

This study describes the synthesis and characterization of an amphiphilic construct intended to recruit SH‐containing molecules to membranes. The construct consists of 1) an aliphatic chain to enable anchoring within membranes, 2) a maleimide moiety to react with the sulfhydryl group of a soluble (bio)molecule, and 3) a fluorescence moiety to allow the construct to be followed by fluorescence spectroscopy and microscopy. It is shown that the construct can be incorporated into preformed membranes, thus allowing application of the approach with biological membranes. The close proximity between the fluorophore and the maleimide moiety within the construct causes fluorescence quenching. This allows monitoring of the reaction with SH‐containing molecules by measurement of increases in fluorescence intensity and lifetime. Notably, the construct distributes into laterally ordered membrane domains of lipid vesicles, which is probably triggered by the length of its membrane anchor. The advantages of the new construct can be employed for several biological, biotechnological, and medicinal applications.     

Catalytically active membranes for esterification: A review

Esterification is an important process in the food industry and can be carried out via homogeneous or heterogeneous catalysis. The homogeneous catalyst, despite providing high conversion, can cause corrosion in reactors, which is not observed with the use of heterogeneous catalysts. However, some of these catalysts require a high process temperature and may lose their catalytic activity with reuse. Thus, catalytic membranes have been proposed as a promising alternative. The combination of cataly...