Screening of lactic acid bacteria isolates from dairy and cereal products for exopolysaccharide production and genes involved

Scanning electron microscopy (SEM) studies revealed that exposure to 4lethal alkaline stress induced statistically significant (P < 0.05) changes in mean cell length, radius and volume in Listeria monocytogenes and a derived σ^B deficient mutant. Bacterial morphology was altered at pH values above 9.0, to include single filamentous or elongated chain forms. Such filamentation and chain formation was observed in the parent strain and in the σ^B deficient strain, and in buffered and non-buffered media. Giemsa staining revealed that the filaments were multi-nucleate, with nucleoids spaced along the length of the atypical cells. In buffered media, longer alkaline exposure was associated with increases in the frequency and length of filamentation. In non-buffered medium, longer exposure was associated with gradual decline in length and the frequency of observation of filaments. Transfer of alkaline treated cells to neutral conditions was associated with the formation of septa within filaments, cell division, and a rapid return to normal morphology, i.e. within 3 h. The observed effects, and their reversibility, may be important in increasing the alkaline tolerance of this pathogen during phagocytosis within the innate human immune system response, and in adaptation/survival in food environments treated with alkali detergents and/or sanitisers. Such atypical cells may be associated with increased survival of L. monocytogenes in adverse environments and may also contribute to qualitative and quantitative underestimation of this important pathogen in food processing environments, with potential implications in public health.     

Effect of sourdough on quality and acceptability of wheat flour tortillas

As an alternative on the search for functional food products, this study evaluated the use of sourdough in the preparation of wheat flour tortillas. The sourdough was elaborated with Lactobacillus sanfranciscensis and the wheat flour tortillas were prepared with different concentrations of mother sponge (5%, 15%, and 25%) and fermentation times (1 and 3 h) at room temperature (25 ± 2 °C). Quality (diameter, height, color, pH, stretchability scores, and Kramer shear cell results) of wheat tortillas was evaluated after 24 h of preparation. The mother sponge concentration and fermentation time affected some quality parameters and acceptability properties (taste, aroma, color, opacity, and rollability). In addition, the sourdough tortillas had higher stretchability values than control tortillas. Since most of the prepared sourdough tortillas had acceptability values similar to those of tortilla controls, the introduction of sourdough is a viable means to incorporate additional nutritional and nutraceutical value into wheat tortillas.     

Statistical Evaluation of Real-Time PCR Protocols Applied to Quantify Genetically Modified Maize

Real-time PCR (RTi-PCR) is the technique of choice for event-specific quantification of genetically modified organisms (GMOs) by determining the amount of event with respect to a species-specific reference gene. Reference genes can be amplified from the genome extracted from Certified Reference Materials (CRMs) or from ad hoc designed plasmids. In the present study, we statistically evaluate the performance of RTi-PCR protocols for GM maize MON810 event by using both genomic DNA from conventional CRMs and a plasmid containing sequences representative of four maize species-specific reference genes. The significance of simple and interaction effects of several variables included in the experimental design on DNA quantification methods and RTi-PCR were evaluated and discussed. Statistically significant differences on Ct values may have an impact on the GMOs quantification and consequently on the compliance of GM quantification-established legal thresholds. Our results confirm the reliability of the plasmid as alternative calibrant for the calculation of GMOs copy number.     

The effects of method of castration,rearing condition and diet on sensory quality of pork assessed by a trained panel

Beside surgical castration possible alternatives helping to reduce the incidence of boar taint in cooked pork are rearing conditions, immunocastration and feeding strategies for entire males known to lower the skatole levels. The goal of this study was to assess the effects of these alternatives on the sensory acceptability of pork. In experiment 1, carcasses from barrows, entire males (EM) and entire males fed raw potato starch (EM+) 7 d before slaughter were selected based on the androstenone (≤ 2 µg/g) and skatole (≤ 0.32 µg/g) levels. In experiment 2, carcasses from barrows, immunocastrates (IC), entire males either group-penned (EMG) or individually penned (EMP) were selected based on the aforementioned criteria. Boar odour and boar flavour intensities of longissimus dorsi (LD) and neck chops were evaluated by trained panellists. Boar odour and flavour scores were higher (P < 0.01) in neck than LD chops. Although skatole tissue levels in barrows and EM+ were similar (P > 0.05), boar odour and flavour scores were greater (P < 0.05) in EM+ than barrows. In experiment 2, scores for boar odour and flavour were lower (P < 0.05) in pork from barrows and IC than EMP, with intermediate values for EMG. In conclusion, we observed a discrepancy between the known boar taint compounds androstenone and skatole and sensory acceptability, which indicates that other factors influenced the perception of boar taint. Thus, surgical castration with or without anesthesia or immunocastration are still the safest methods to avoid boar taint.