Agents Of Food Spoilage Research Articles

Antimicrobial activity of aqueous extract of Laetiporus sulphureus (Bull.: Fr.) Murill

Wood-rotting basidiomycete, Laetiporus sulphureus (Bull.: Fr.) Murill., also known as chicken of the woods, is known for its nutritional value. In this study, aqueous extract obtained from L. sulphureus was investigated for its antimicrobial properties using microdilution in vitro assay. Plant, animal and human pathogens, as well as food spoilage agents, were tested. Aqueous extract obtained from L. sulphureus showed strong activity against the tested microorganisms in a dose dependent manner. Considering that there is a constant emerging of pathogen resistance to the known synthetic agents, there is an undeniable need for new therapeutical drugs and preservatives in food industry. Thus, these results that indicate activity of natural products may be of practical use.

Physicochemical changes induced in carp ( Cyprinus carpio) fillets by high pressure processing at low temperature

Raw carp fillets ( Cyprinus carpio) were vacuum packed and pressurized at 100, 140, 180 and 200 MPa at 4 °C for 15 and 20 min, and then monitored for changes in the lipid fraction, color and electrophoretic profiles. The values of thiobarbituric acid (TBA) reactive substances in the samples increased with pressure and pressurization time. Similar results were obtained for free fatty acids (FFA) levels formed as a result of pressure treatment. The CIE color values, i.e., L ⁎ (lightness), a ⁎ (redness) and b ⁎ (yellowness) of the carp fish fillets also increased with pressure and pressurization time, and the results obtained attest to the importance of establishing treatment conditions for various fish species when processing these food products in order to minimize changes in their appearance and flavor characteristics. Industrial relevance High pressure processing is finding increasing use in the food industry because of its relative advantages versus other food processing methods in eliciting minimal changes in the flavor and nutritional qualities of the final product. High pressure treatment is able to achieve this via its effects on the two causative agents of food spoilage, namely autolysis as well as microbial growth and metabolism. High pressure processing has been used commercially to produce food products such as raw oysters, guacamole, and ham and fruit juices in the US; and to produce jams, jellies, fish and meat products, salad dressing, ham, fruit juices and yogurt in Europe and Japan. However, in spite of the notion that high pressure processing results in minimal changes in food products, it is also common knowledge that the technology induces important changes in the texture and appearance of raw fish would be influenced by temperature at which the pressurize treatment was conducted. This paper illustrates the changes induced in raw carp flesh by pressurization at different temperatures.

Analysis of the action of compounds that inhibit the germination of spores of Bacillus species

To determine the mechanism of action of inhibitors of the germination of spores of Bacillus species, and where these inhibitors act in the germination process. Spores of various Bacillus species are significant agents of food spoilage and food-borne disease, and inhibition of spore germination is a potential means of reducing such problems. Germination of the following spores was studied: (i) wild-type B. subtilis spores; (ii) B. subtilis spores with a nutrient receptor variant allowing recognition of a novel germinant; (iii) B. subtilis spores with elevated levels of either the variant nutrient receptor or its wild-type allele; (iv) B. subtilis spores lacking all nutrient receptors and (v) wild-type B. megaterium spores. Spores were germinated with a variety of nutrient germinants, Ca2+-dipicolinic acid (DPA) and dodecylamine for B. subtilis spores, and KBr for B. megaterium spores. Compounds tested as inhibitors of germination included alkyl alcohols, a phenol derivative, a fatty acid, ion channel blockers, enzyme inhibitors and several other compounds. Assays used to assess rates of spore germination monitored: (i) the fall in optical density at 600 nm of spore suspensions; (ii) the release of the dormant spore's large depot of DPA; (iii) hydrolysis of the dormant spore's peptidoglycan cortex and (iv) generation of CFU from spores that lacked all nutrient receptors. The results with B. subtilis spores allowed the assignment of inhibitory compounds into two general groups: (i) those that inhibited the action of, or response to, one nutrient receptor and (ii) those that blocked the action of, or response to, several or all of the nutrient receptors. Some of the compounds in groups 1 and 2 also blocked action of at least one cortex lytic enzyme, however, this does not appear to be the primary site of their action in inhibiting spore germination. The inhibitors had rather different effects on germination of B. subtilis spores with nutrients or non-nutrients, consistent with previous work indicating that germination of B. subtilis spores by non-nutrients does not involve the spore's nutrient receptors. In particular, none of the compounds tested inhibited spore germination with dodecylamine, and only three compounds inhibited Ca2+-DPA germination. In contrast, all compounds had very similar effects on the germination of B. megaterium spores with either glucose or KBr. The effects of the inhibitors tested on spores of both Bacillus species were largely reversible. This work indicates that inhibitors of B. subtilis spore germination fall into two classes: (i) compounds (most alkyl alcohols, N-ethylmaleimide, nifedipine, phenols, potassium sorbate) that inhibit the action of, or response to, primarily one nutrient receptor and (ii) compounds [amiloride, HgCl2, octanoic acid, octanol, phenylmethylsulphonylfluoride (PMSF), quinine, tetracaine, tosyl-l-arginine methyl ester, trifluoperazine] that inhibit the action of, or response to, several nutrient receptors. Action of these inhibitors, is reversible. The similar effects of inhibitors on B. megaterium spore germination by glucose or KBr indicate that inorganic salts likely trigger germination by activating one or more nutrient receptors. The lack of effect of all inhibitors on dodecylamine germination suggests that this compound stimulates germination by creating channels in the spore's inner membrane allowing DPA release. This work provides new insight into the steps in spore germination that are inhibited by various chemicals, and the mechanism of action of these inhibitors. The work also provides new insights into the process of spore germination itself.