Lactobacillus casei strains isolated from cheese reduce biogenic amine accumulation in an experimental model

Tyramine and histamine are the biogenic amines (BAs) most commonly found in cheese, in which they appear as a result of the microbial enzymatic decarboxylation of tyrosine and histidine respectively. Given their toxic effects, their presence in high concentrations in foods should be avoided. In this work, samples of three cheeses (Zamorano, Cabrales and Emmental) with long ripening periods, and that often have high BA concentrations, were screened for the presence of BA-degrading lactic acid bacteria (LAB). Seventeen isolates were found that were able to degrade tyramine and histamine in broth culture. All 17 isolates were identified by 16S rRNA sequencing as belonging to Lactobacillus casei. They were typed by plasmid S1-PFGE and genomic macrorestriction-PFGE analysis. Two strains (L. casei 4a and 5b) associated with high degradation rates for both BAs were selected to test how this ability might affect histamine and tyramine accumulation in a Cabrales-like mini-cheese manufacturing model. The quantification of BAs and the monitoring of the strains' growth over ripening were undertaken by RP-HPLC and qPCR respectively. Both strains were found to reduce histamine and tyramine accumulation. These two strains might be suitable for use as adjunct cultures for reducing the presence of BAs in cheese.     

Quantification of significant volatile components of pacharán

 Pacharán is a traditional drink from Navarra (Spain). This liqueur is obtained by maceration of sloe berries (Prunus spinosa L.) with aqueous ethanol and subsequent addition of sugar and essential oils of anise (Pimpinella anisum L. or Illicium verum H.). The following volatile components of pacharán were identified and quantified: cis-anethol; trans-anethol; anisaldehyde; benzaldehyde; benzyl alcohol; γ-butyrolactone; 1,1-diethoxyethane; ethyl benzoate; ethyl lactate; diethyl malate (hydroxybutanedioic acid diethyl ester); estragol (methyl chavicol); eugenol [2-methoxy-4-(2-propenyl)-phenol]; 2-furaldehyde; linalool; cis-3-hexen-1-ol; (4-methoxyphenyl)propanone; 2-phenylethanol and vanillin. Received: 3 November 1997 / Revised version: 29 December 1997     

Molecular monitoring of spoilage yeasts during the production of candied fruit nougats to determine food contamination sources

In the present work, we have analysed the yeast microbiota present in a manufacturing plant of candied fruits and nougats. Four yeasts species (Zygosaccharomyces bailii, Zygosaccharomyces rouxii, Sporobolomyces roseus, and Debaryomyces hansenii) and a filamentous fungi (Nectria mauriiticola) were identified according to restriction analysis of 5.8S-ITS rDNA. These identifications were subsequently confirmed by sequencing the D1/D2 domain of the 26S rRNA gene. Z. rouxii and Z. bailii were isolated at high frequency along the whole manufacturing process. Since food alteration by Z. bailii and Z. rouxii is the cause of important economic losses for the food industry, there is a need for differentiating yeasts at the strain level as an essential part of quality control programs in this industry. For this purpose, we have tested the performance of three molecular techniques (RFLP mtDNA, RAPD-PCR, and microsatellite with (GAC)5 and (GTG)5 primers) to differentiate strains belonging to these two Zygosaccharomyces species. Those techniques with the best discriminatory power were applied to differentiate Zygosaccharomyces species isolates. The results of this analysis indicate that one strain of Z. bailii and two strains of Z. rouxii were involved in the spoilage of candied fruits. Moreover, the Z. bailii strain was also present in the spoiled nougat, hence being responsible of this alteration.     

Chemical affinities between the major volatile compounds present in a grape pomace distillate

BACKGROUND: The distillation of vinification by‐products to obtain alcoholic drinks is potentially an important source of income for the producing countries and avoids the environmental problem of waste management. Traditional technologies of distillation involve an important cost in terms of time and staff. Nowadays, companies install new distillation equipment, with high capacity and equipped with rectification columns, which is an important advance. Nevertheless, few studieshave been published concerning their correct management. In this study, the major volatile compounds were determined by gas chromatography in 61 samples of grape pomace distillate, corresponding to the fractions collected during seven complete distillation cycles. RESULTS: With a high degree of significance, the concentrations of 1,1‐diethoxyethane, propanol, hexanoate and ethyl acetate present positive correlations with the ethanol. However, those of benzyl alcohol, 2‐phenylethanol, furfurol, lactate, ethyl mirystate and diethyl succinate, were negative, which indicates that both groups of compounds were vented in the fractions of major or minor alcoholic degree, respectively. In addition, knowledge of the relationships between the volatile compounds contributes to improved management of an industrial distillation unit. CONCLUSION: The correlations established between the concentrations of the different volatile compounds indicate their physico‐chemical affinities or their biochemical origin. Copyright © 2009 Society of Chemical Industry     

Comparison of acids on the induction of an Acid Tolerance Response in Salmonellatyphimurium, consequences for food safety

Salmonellatyphimurium inactivation at pH 3.0 in Brain Heart Infusion (BHI) and Meat Extract (ME) was studied using stationary-phase cells grown in non-acidified BHI (pH 7.4) and ME (pH 6.6) and acidified BHI and ME at pH values of 6.4, 5.4 and 4.5 with acetic, ascorbic, citric, lactic, malic and hydrochloric acids. Cells grown in buffered BHI (pH 7.0) were used as non-acid adapted control cells.     

An access detection and machine cycle tracking system for machine safety

Abrasive water jet (AWJ) machining is characterized by its versatility, i.e., it can be applied to a wide variety of materials. Currently, one important application is for manufacturing gem artifacts, especially agate, which is the largest gemological material produced in the state of Rio Grande do Sul. However, one of the main obstacles to its popularization is the cost associated with the process, due to the high abrasive consumption required for a good quality surface finish. In this sense, this research paper presents a study of the influence of the main process parameters (traverse speed and abrasive mass flow rate) on the surface finish of agates machined by AWJ. The experimental procedure used three different traverse speeds, four abrasive mass flow rate in two different thicknesses of agate’s plates. Surface roughness and angle of striation marks were observed for different depths from the jet entrance surface. Results were analyzed using analysis of variance (ANOVA). Through the study, it was found that the machined surface finish varies according to the depth from the entrance surface of the abrasive jet. Also, it was concluded that the surface finish of the machined surface by AWJ (surface roughness and striation marks) of the agate’s plates machined by AWJ exhibits similar results for both thicknesses tested. ANOVA showed that the traverse speed is more significant than abrasive mass flow rate for the material studied with respect to the surface finish. Thus, for a small material thickness, it is possible to use high traverse speed and low abrasive mass flow rate which makes the process more economical.