R.E. Simard

Antibacterial activity of selected fatty acids and essential oils against six meat spoilage organisms

The antibacterial activity of selected fatty acids and essential oils was examined against two gram-negative (Pseudomonas fluorescens and Serratia liquefaciens) and four gram-positive (Brochothrix thermosphacta, Carnobacterium piscicola, Lactobacillus curvatus, and Lactobacillus sake) bacteria involved in meat spoilage. Various amounts of each preservative were added to brain heart infusion or MRS (deMan, Rogosa and Sharpe) agars, and the minimum inhibitory concentration was determined for each organism. Essential oils were analysed by gas-liquid chromatography to determine the concentration of selected components commonly found in spices. B. thermosphacta, P. fluorescens and S. liquefaciens were not affected by fatty acids, and generally overcame the inhibitory effect of essential oils after 24 h of exposure. Among the fatty acids, lauric and palmitoleic acids exhibited the greatest inhibitory effect with minimum inhibitory concentrations of 250 to 500 micrograms/ml, while myristic, palmitic, stearic and oleic acids were completely ineffective. For essential oils, clove, cinnamon, pimento, and rosemary were found to be the most active. The 1/100 dilution of those oils inhibited at least five of the six tested organisms. A relationship was found between the inhibitory effect of essential oils and the presence of eugenol and cinnamaldehyde.

Inhibition of surface spoilage bacteria in processed meats by application of antimicrobial films prepared with chitosan

A study was undertaken to evaluate the feasibility of using antimicrobial films, designed to slowly release bacterial inhibitors, to improve the preservation of vacuum-packaged processed meats during refrigerated storage. The antimicrobial films were prepared by incorporating acetic or propionic acid into a chitosan matrix, with or without addition of lauric acid or cinnamaldehyde, and were applied onto bologna, regular cooked ham, or pastrami. At various times during storage, packages were opened and the amounts of antimicrobial agents remaining in the chitosan matrix were measured. Regardless of film composition or meat product type, propionic acid was nearly completely released from the chitosan matrix within 48 h of application, whereas release of acetic acid was more limited, with 2-22% of the acid remaining in chitosan after 168 h of storage. Addition of lauric acid, but not cinnamaldehyde, to the chitosan matrix generally reduced the release of acetic acid significantly (P < or = 0.05) and the release was more limited onto bologna than onto ham or pastrami. In addition, the efficacies of the various films for inhibiting bacterial growth were tested against indigenous lactic acid bacteria and Enterobacteriaceae, and against Lactobacillus sakei or Serratia liqueficiens, surface-inoculated onto the meat products. Whereas lactic acid bacteria were not affected by the antimicrobial films under study, the growth of Enterobacteriaceae and S. liquefaciens was delayed or completely inhibited as a result of film application. Strongest inhibition was observed on drier surfaces (bologna), onto which acid release was slower, and with films containing cinnamaldehyde, as a result of its greater antimicrobial activity under these conditions.

Bitter flavour in dairy products. II. A review of bitter peptides from caseins: their formation, isolation and identification, structure masking and inhibition

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. Bitter flavour in dairy products. II. A review of bitter peptides from caseins: their formation, isolation and identification, structure masking and inhibition L Lemieux, Re Simard

Nutrient composition, protein quality and antinutritional factors of some varieties of dry beans (Phaseolus vulgaris) grown in Burundi

Abstract Four varieties of dry beans ( Phaseolus vulgaris ) grown in four different areas of Burundi were analyzed for moisture, protein, fat, ash, mineral (potassium, calcium, magnesium, iron, copper, zinc, and phosphorus), essential amino acids (isoleucine, leucine, lysine, methionine, phenylalanine, threonine, valine) and antinutritional factors (raffinose oligosaccharide, trypsin inhibitor, hemagglutinin, tannin and phytic acid) contents. In-vitro digestibility of dry bean proteins was also evaluated. The concentrations observed for the proximate composition, protein quality, and antinutritional factors varied significantly ( P −3 /g, 2·15 HU × 10 −3 /mg, 14·99 mg catechin equivalent/g and 16·50 mg/g. The levels obtained for different nutrients (except for some minerals) and antinutrients were in agreement with those found in dry beans in other areas of the world. Protein digestibility ranged from 67·47% (Calima variety from Kirimiro) to 71·99% (A410 variety from Imbo). These values were comparable to those obtained in other countries. Statistical analyses of data confirmed that nutrient content, protein digestibility and undesirable factors were influenced by both variety and locality. Relationships between some dry bean nutrients and between antinutritional factors and protein digestibility were also observed.

Influence of growth conditions on production and activity of mesenterocin 5 by a strain of Leuconostoc mesenteroides

The effects of various parameters on production and activity of mesenterocin 5, a bacteriocin produced by Leuconostoc mesenteroides subsp. mesenteroides UL5, were investigated. Titres of bacteriocin and minimum inhibitory concentration values were determined by a critical dilution micromethod, using a sensitive strain of Listeria ivanovii as an indicator. Production of the antimicrobial compound was optimal at 37 and 40°C after 9 h of incubation, and was maximized in an aerobic fermentor maintained at pH 5.0. Tween 80 was a major factor in increasing mesenteroxin 5 production and specific production. Large quantities of bacteriocin could be obtained in whey and in whey permeate supplemented with yeast extract in the presence of the surfactant (0.1%). Most of the Listeria strains tested including L. monocytogenes were highly sensitive to the bacteriocin in the pH range 5.5 to 6.0 and at a temperature of 20 to 25°C.

Effects of soaking, cooking and fermentation on composition, in-vitro starch digestibility and nutritive value of common beans.

A common bean variety, grown in Burundi, was either fermented, soaked and/or cooked, and then assessed for nutrient composition, in-vitro starch digestibility and protein nutritive value. A decrease in ash, most minerals, vitamins, and some essential amino acids was noted for soaked, cooked and soaked-cooked beans. Compared to untreated beans, soaking decreased soluble sugar (9.8 percent) but increased starch (7.3 percent) and soluble fiber (16.9 percent). In cooked beans, an increase in soluble sugar (1.5 percent), and a decrease in thiamine (81.7 percent), starch (24.6 percent) and soluble fiber (16.6 percent) and nitrogen (2.9 percent) contents were observed. Crude fiber (6.9 percent) and starch (10.0 percent) increased while fat (17.6 percent), fatty acids (linoleic: 10.7 percent; linolenic: 14.3 percent) and soluble sugars (25.4 percent) and nitrogen (14.4 percent) decreased in soaked-cooked beans. Fermentation increased potassium (11.6 percent), soluble fiber (18.9 percent), and some amino acids but decreased fatty acids (linoleic: 13.5 percent; linolenic: 19.9 percent), soluble sugar (75.2 percent) and vitamin (riboflavin: 41.0 percent; niacin: 24.5 percent) contents in common beans. However, the in-vitro starch digestibility was greatly improved (12.3 percent) by cooking while it decreased in soaked beans (29.2 percent). Soaking-cooking and fermentation did not have any significant effect on the digestibility of common bean starch. Finally, among the five treatments applied to common beans, only fermentation showed a significant improvement (8.3 percent) on the protein nutritive value of this legume.

Influence of the fat content of Cheddar cheese on retention and localization of starters

Abstract Microbiological counts of fat-free, 50% reduced-fat and full-fat Cheddar cheeses were obtained to determine the population of starter bacteria in the different cheeses. Microbiological counts and observations on the cheese curd by transmission electron microscopy indicated that bacterial populations in the curd were directly related to the fat content of cheese. Electron microscopy examinations of cheeses ripened for less than one month showed that cells were either directly in contact with the fat globule membrane or located at the casein-fat interface. However, a higher number of bacterial cells appeared to be in close contact with the fat globule membrane. After one and two months of ripening, the number of ghost cells increased and bacteria seemed to be embedded in the milk fat globule membrane or directly in contact with the inside of fat globules.

Inhibitory Effect of Organic Acids upon Meat Spoilage Bacteria

The relative ability of acetic, benzoic, citric, lactic, propionic, and sorbic acids to inhibit the growth of six common meat spoilage bacteria ( Brochothrix thermosphacta , Carnobacterium piscicola , Lactobacillus curvatus , Lactobacillus sake , Pseudomonas fiuorescens , and Serratia liquefaciens ) was compared under otherwise optimum conditions (BHI or MRS broths; 20°C). Because of their low solubility in the growth media, benzoic and sorbic acids could only be used in low concentrations (below 0.15% [wt/vol]) and did not efficiently inhibit bacterial growth. All other acids totally inhibited growth at concentrations ranging from 0.1 % to 1% (wt/vol). On a weight basis, acetic acid was found to be the most inhibitory, followed by propionic. lactic, and citric acid, while the order of efficiency was reversed (citric> lactic> propionic> acetic) when the acid concentrations were expressed on a molar basis or when the acid effectiveness was evaluated relative to the concentration of undissociated molecules. Overall, the lactobacilli were the bacteria most resistant to the action of organic acids, followed by P. fiuorescens and S. liquefaciens , while B. thermosphacta and C. piscicola were considerably more sensitive.

Detection of Campylobacter jejuni in food and poultry viscera using immunomagnetic separation and microtitre hybridization

Thermophillic Campylobacter and Camp. jejuni were detected from samplesof chicken liver, gall bladder, muscle and contaminated milk and chicken meat after anenrichment step by using immunomagnetic capture of cells with monoclonal antibody againsta specific outer membrane protein of thermophilic Campylobacter. The detection ofcaptured cells was achieved using two different hybridization methods. In one of the methods,the captured cells were lysed by guanidine isothiocyanate and the 23S rRNA wasreacted with a microtitre plate‐immobilized rDNA probe specific for thermophilicCampylobacter. In the other method, the captured cells were subjected to lysis byultrasonication and the genomic DNA reacted with a microtitre plate‐immobilized RNAprobe specific for Camp. jejuni. Detection of the RNA–DNA hybrids formed in the wells was carried out using a monoclonal anti‐RNA–DNA hybrid antibody.

Note: Genetic and biochemical characterization of nisin Z produced by Lactococcus lactis ssp. lactis biovar. diacetylactis UL 719

The bacteriocin produced by Lactococcus lactis ssp. lactis biovar. diacetylactis UL 719 was purified and characterized. Two peaks exhibiting antimicrobial activity were obtained after purification. Primary structure of the peptide of major peak 2 was identical to that of nisin Z when determined by Edman degradation and confirmed by DNA sequence analysis. The molecular mass as determined by mass spectrometry was 3346·39 ± 0·40 Da for peak 1 and 3330·39 ± 0·27 Da for peak 2, which suggests that peak 1 may correspond to an oxidized form of nisin Z. The two purified peaks exhibiting xrantimicrobial activity appear to correspond with the oxidized and native forms of nisin Z.