Ling Heather Honey Authentication by Thixotropic Parameters

This paper assesses the actual reliability of four rheological parameters to help describe honeys that exhibit non-Newtonian behavior, being the most representative of which, ling heather (Calluna vulgaris (L.) Hull) honeys. Sampling included a representative number of unifloral ling heather honeys, non-unifloral honeys close to ling heather uniflorality, and other non-unifloral honeys containing ling heather. All experiments were performed at 25 °C and consisted on researching viscosity curves at different shear rates, as well as the time dependency of honey samples at a constant shear rate. Viscosity curves were correctly fitted by the Ostwald-de Waele model. Consistency coefficients (k) and flow behavior indexes (n) were calculated, and the Weltmann model was used to determine the stress decay behavior. The influence of honey moisture on k value was also researched. Hysteresis area and time-dependent thixotropic index B proved to be the most suitable parameters for a reliable ling heather honey authentication.     

Moisture loss and oil uptake during deep fat frying of “Kroštula” dough

The mechanism of moisture transfer by diffusion and uptake of frying oil was studied during deep fat frying of Krotula dough with an initial moisture content of 0.4358 kg/kg (db). The experimental data were found to fit well to a first-order exponential model for moisture transfer (with a regression coefficient of 0.99). The effective moisture diffusivity of Krotula dough was determined for two periods of moisture loss (intensive in first 60 s and constant after 60 s of frying). In the frying range 0–60 s at temperatures of 160, 170, 180 and 190±1 °C, the effective moisture diffusivity values were 5.837, 6.607, 8.472 and 9.728×10^–9 m²/s, from which the activation energy (30 kJ/mol) was calculated by using an Arrhenius-type equation. The effective oil diffusivity values of Krotula dough in the frying time range 0–210 s at temperatures of 160, 170, 180 and 190±1 °C were 0.932, 1.135, 1.094 and 1.054×10^–9 m²/s, from which the activation energy (5.5 kJ/mol) was calculated by using an Arrhenius-type equation.     

Effects of propentofylline on CNS remyelination in the rat brainstem

Propentofylline (PPF) is a xanthine derivative with pharmacological effects distinct from those of the classical methylxanthines. It depresses activation of microglial cells and astrocytes which is associated with neuronal damage during neural inflammation and hypoxia. The aim of this study was to evaluate whether PPF had the capacity of affecting glial cells behavior during the process of demyelination and remyelination following ethidium bromide (EB) gliotoxic injury. EB injection into the CNS is commonly used as an experimental demyelinating model inducing local oligodendroglial and astrocytic death, which results in primary demyelination, blood–brain barrier and glia limitans disruption and Schwann cells invasion. Sixty Wistar rats were divided into four different groups receiving 10 microlitres of 0.1% EB or 0.9% saline solution into the cisterna pontis and treated or not with the xanthine. PPF treatment was done using 12.5 mg/kg/day by the intraperitonial route for 31 days of the experimental period. The rats were euthanized from 7 to 31 days after EB injection and brainstem sections were collected and processed for light and transmission electron microscopy studies. Results from both groups were compared by using a semi‐quantitative method developed for documenting in semithin sections the extent and nature of remyelination of demyelinating lesions. Results showed that PPF administration after EB injection significantly increased both oligodendroglial and Schwann cell remyelination at 31 days (mean remyelination scores of 3.67 ± 0.5 for oligodendrocytes and 1.27 ± 0.49 for Schwann cells) compared to untreated animals (scores of 3.19 ± 0.57 and 0.90 ± 0.33, respectively). Microsc. Res. Tech. 77:23–30, 2014. © 2013 Wiley Periodicals, Inc.     

Citrus Extracts as Inhibitors of Quorum Sensing,Biofilm Formation and Motility of Campylobacter jejuni

Quorum Sensing (QS), a signaling system present in bacteria, influences the expression of a variety of virulence factors. This study investigated the ability of citrus extracts to inhibit the activity of AI-2 molecules that mediate QS in Campylobacter jejuni and the effects of these extracts on motility, biofilm formation and expression of flaA-B. Cultures of C. jejuni were exposed to extracts of Citrus limon, Citrus medica and Citrus aurantium peels at various concentrations. Swarm motility tests were performed in Muller Hinton agar; biofilm formation was determined colorimetrically in microtiter plates; AI-2 activity was measured with a bioluminescence assay using V. harveyi; and flaA-B expression was determined by qRT-PCR. Treatment with C. limon or C. medica peel extract reduced swarm motility 44–59%, whereas treatment with C. aurantium extract reduced swarm motility 35–40%. Biofilm formation was reduced 60–75 % by these extracts, depending on extract concentration and /or strain tested. All three citrus extracts decreased AI-2 activity by about 90 %, and at 75 % of MBC, significantly (P ≤ 0.05) reduced expression of flaA-B. These findings provide preliminary metabolic and molecular insights into the effects of edible antimicrobials on QS and virulence factors of C. jejuni.     

Evaluation of consumer-style cooking methods for reduction of Escherichia coli O157:H7 in ground beef

The objective of this study was to evaluate the thermal inactivation of Escherichia coli O157:H7 in ground beef cooked to an internal temperature of 71.1 degrees C (160 degrees F) under conditions simulating consumer-style cooking methods. To compare a double-sided grill (DSG) with a single-sided grill (SSG), two different cooking methods were used for the SSG: for the one-turnover (OT-SSG) method, a patty was turned once when the internal temperature reached 40 degrees C, and for the multiturnover (MT-SSG) method, a patty was turned every 30 s. Patties (100 g, n = 9) inoculated with a five-strain mixture of E. coli O157: H7 at a concentration of 10(7) CFU/g were cooked until all three temperature readings (for two sides and the center) for a patty were 71.1 degrees C. The surviving E. coli O157:H7 cells were enumerated on sorbitol MacConkey (SMAC) agar and on phenol red agar base with 1% sorbitol (SPRAB). The order of the cooking methods with regard to the cooking time required for the patty to reach 71.1 degrees C was as follows: DSG (2.7 min) < MT-SSG (6.6 min) < OT-SSG (10.9 min). The more rapid, higher-temperature cooking method was more effective (P < 0.01) in destroying E. coli O157:H7 in ground beef. E. coli O157:H7 reduction levels were clearly differentiated among treatments as follows: OT-SSG (4.7 log10 CFU/g) < MT-SSG (5.6 log10 CFU/g) < DSG (6.9 log10 CFU/g). Significantly larger numbers of E. coil O157:H7 were observed on SPRAB than on SMAC agar. To confirm the safety of ground beef cooked to 71.1 degrees C, additional patties (100 g, n = 9) inoculated with lower concentrations of E. coli O157:H7 (10(3) to 10(4) CFU/g) were tested. The ground beef cooked by the OT-SSG method resulted in two (22%) of nine samples testing positive after enrichment, whereas no E. coli O157:H7 was found for samples cooked by the MT-SSG and DSG methods. Our findings suggest that consumers should be advised to either cook ground beef patties in a grill that cooks the top and the bottom of the patty at the same time or turn patties frequently (every 30 s) when cooking on a grill that cooks on only one side.     

Effect of amylose/amylopectin ratio and extent of processing on the physical properties of expanded maize starches

Low-density expanded starchy products are often desirable, particularly in the snack food industry. Levels of shear and amylose are often deemed crucial factors for expansion. In this study, maize starches containing low (waxy), normal and high levels of amylose were compared after processing. Low shear processing used a popping head (similar to a rice-cake machine), while high shear (~450 kJ kg⁻¹) samples (pellets and directly expanded) were created using twin-screw thermomechanical extrusion. Native starches and ground extruded materials (<106 µm) were popped using the same conditions (230 °C, 4 s, water content 12% wwb). All samples tested created fused aerated cakes, which had little or no remaining crystallinity, except for the directly popped waxy sample, which retained ~17% of its original crystallinity. Water absorbances and solubilities were influenced greatly by the starch source and marginally by the amount of processing. On processing, waxy samples showed increased solubility while those with normal amylose content had greater absorption. The densities of all the popped samples were similar despite marked differences in shear regime history and the major variations in the amylose and amylopectin ratios. These results challenge the expected relationships between shear and different starches’ potential to expand.     

Effect of Sugar Catabolite Repression in Correlation with the Structural Complexity of the Nitrogen Source on Yeast Growth and Fermentation

Biomass and ethanol production by industrial Saccharomyces cerevisiae strains were strongly affected by the structural complexity of the nitrogen source during fermentation in media containing galactose, and supplemented with a nitrogen source varying from a single ammonium salt (ammonium sulfate) to free amino acids (casamino acids) and peptides (peptone). Diauxie was observed at low galactose concentrations independent of nitrogen supplementation. At high sugar concentrations altered patterns of galactose utilisation were observed. Biomass accumulation and ethanol production depended on the nature of the nitrogen source and were different for baking and brewing ale and lager strains. Baking yeast showed improved galactose fermentation performance in the medium supplemented with casamino acids. High biomass production was observed with peptone and casamino acids for the ale brewing strain, however high ethanol production was observed only in the presence of casamino acids. Conversely, peptone was the nitrogen supplement that induced higher biomass and ethanol production for the lager brewing strain. Ammonium salts always induced poor yeast performance. The results with galactose differed from those obtained with glucose and maltose which indicated that supplementation with a nitrogen source in the peptide form (peptone) was more positive for yeast metabolism, suggesting that sugar catabolite repression has a central role in yeast performance in a medium containing nitrogen sources with differing levels of structural complexity.