Isolation of Yersinia from raw meat (pork and chicken) and precooked meat (porcine tongues and sausages) collected from commercial establishments in Mexico City

A total of 160 meat product samples were collected from commercial outlets in Mexico City to investigate the presence of different species of Yersinia by the 4 degrees C enrichment method after 1, 3, 5, and 7 days of incubation using alkaline treatment and isolating in cefsulodin-Irgasan-novobiocin and MacConkey agars with Tween 80. Overall, Yersinia spp. were isolated from 27% of the samples analyzed, whereas 40% of the raw and only 13% of the precooked samples were contaminated. Although 2,970 colonies showed Yersinia characteristics, only 706 (24%) actually corresponded to this genus: 49% were Yersinia enterocolitica, 25% Yersinia kristensenii, 15% Yersinia intermedia, 9% Yersinia frederiksenii, and 2% Yersinia aldovae; 10% corresponded to biotype 2, 2% to biotype 3, and 4% to biotype 4. The presence of Yersinia in raw and cooked meat products represents a health risk for consumers in Mexico, where further clinical studies are needed to assess the epidemiological importance of this pathogen.     

Polysaccharides from Sesamum indicum meal: Isolation and structural features

Defatted Sesamum indicum seed cake was extracted, following two separate sequences, and the effects of extraction medium on yield and composition of the extracts were compared. Polysaccharides extracted sequentially with dilute acid and alkali represented 250 mg/g of defatted meal. The isolated polymers contained arabinan, rhamnogalacturonan I (RG I) and arabinogalactan proteins. Polysaccharides extracted during chlorite treatment and with dilute alkali had a higher proportion of rhamnose, suggesting a more branched variety of polymer. Three extracts, which were further characterized by size exclusion chromatography, gave two overlapping peaks. Structural characterisation of hemicellulosic polysaccharides, isolated with KOH, using specific enzyme hydrolysis, ion exchange chromatography (HPAEC) and matrix assisted laser desorption ionisation-time-of-flight (MALDI-TOF) mass spectroscopy, showed that sesame meal xyloglucan (XG) contained XXXG, XXFG and XXLG, and XLLG (named according to Fry et al., 1993) as the major building sub-units in the ratio of 1:0.9:0.3. Hydrolysis with endo-β-(1 → 4)-d-xylanase and analysis of the xylan derived oligosaccharides showed the presence of monomeric xylose (40%), xylobiose (46%) and acidic xylan oligosaccharides containing 4-O-methyl-d-glucuronic acid residues (14%).     

Selective Extraction of (−)Epigallocatechin Gallate from Green Tea Leaves Using Two-Stage Infusion Coupled with Membrane Separation

A novel method for the extraction of (−)epigallocatechin gallate of high purity from green tea leaves is proposed in this study. The method comprised a two-stage water-based extraction followed by successive use of microfiltration and ultrafiltration. Microfiltration was used as a pretreatment to ultrafiltration. The best process conditions of each unit operation were estimated by performing well-planned experimentations. The clarified liquor was dried to powder by freeze drying. Chemical analyses revealed that the tea powder contained about 90% of polyphenols. The purity of (−)epigallocatechin gallate was found to be about 80%, while its average yield was 1.22 g/l. The method outlined in this study may have remarkable importance for the bulk production of high-purity (−)epigallocatechin gallate with potential application in pharmaceutical, cosmetic, and food-processing industries. Besides being a green process, this method can be easily scaled up for the commercial production of (−)epigallocatechin gallate.     

A Bayesian approach to the effect of selection for growth rate on sensory meat quality of rabbit

The effect of selection for growth rate on the sensory characteristics of rabbit meat was assessed by comparing a selected and a control population of rabbits. Embryos belonging to generation 7th were frozen, thawed and implanted in does in order to produce the control group. The control group was formed from the offspring of the embryos belonging to the 7th generation. Selected animals belonging to 21st generation (S) were compared with animals of the control group (C), both were contemporary. Forty animals per group were slaughtered at 9-weeks-old. The sensory analysis was carried out on samples of the Longissimus dorsi muscle. The parameters evaluated were: intensity of rabbit flavour (IRF), aniseed odour (AO), aniseed flavour (AF), liver flavour (LF), tenderness (T), juiciness (J), fibrousness (F). A Bayesian analysis was performed. The ratio of the selection and control effects was analysed. There was a difference between the selected and control groups for IRF, AO, AF and LF. Conversely, no differences were found in T, J and F between groups. Selected group had 3% and 23% higher values of IRF and LF, respectively, than the control group. A relevant effect of selection on AO and AF appeared (probability of relevance P(r)=1), with lower values for selected animals. There was a difference between male and female groups for IRF, but this was not relevant. No differences between sexes were found for the rest of the characteristics evaluated. Selection for growth rate did not affect the main sensory characteristics of meat, like T and J but, it had a negative effect on some flavour characteristics.     

LED lighting and seasonality effects antioxidant properties of baby leaf lettuce

We report on the application of supplementary light-emitting diode (LED) lighting within a greenhouse for cultivation of red, green and light green leaf baby lettuces (Lactuca sativa L.) grown under natural illumination and high-pressure sodium (HPS) lamps (16-h; PPFD-170 μmol m⁻² s⁻¹) during different growing season. Supplementary lighting from blue 455/470 nm and green 505/530 nm LEDs was applied (16-h; PPFD-30 μmol m⁻² s⁻¹). Our results showed that to achieve solely a positive effect is complicated, because metabolism of antioxidant properties in lettuce depended on multicomponent exposure of variety, light quality or seasonality. The general trend of a greater positive effect of supplemental LED components on the vitamin C and tocopherol contents was in order: 535 > 505 > 455 > 470 nm; on the total phenol content: 505 > 535 = 470 > 455 nm; on the DPPH free-radical scavenging capacity: 535 = 470 > 505 > 455 nm; on the total anthocyanins: 505 > 455 > 470 > 535 nm. Further investigations are needed for understanding the mechanism and interaction between antioxidants and light signal transduction pathways.     

Enzymatic changes in pectic polysaccharides related to the beneficial effect of soaking on bean cooking time

BACKGROUND: Cooking time decreases when beans are soaked first. However, the molecular basis of this decrease remains unclear. To determine the mechanisms involved, changes in both pectic polysaccharides and cell wall enzymes were monitored during soaking. Two cultivars and one breeding line were studied. RESULTS: Soaking increased the activity of the cell wall enzymes rhamnogalacturonase, galactanase and polygalacturonase. Their activity in the cell wall was detected as changes in chemical composition of pectic polysaccharides. Rhamnose content decreased but galactose and uronic acid contents increased in the polysaccharides of soaked beans. A decrease in the average molecular weight of the pectin fraction was induced during soaking. The decrease in rhamnose and the polygalacturonase activity were associated (r = 0.933, P = 0.01, and r = 0.725, P = 0.01, respectively) with shorter cooking time after soaking. CONCLUSION: Pectic cell wall enzymes are responsible for the changes in rhamnogalacturonan I and polygalacturonan induced during soaking and constitute the biochemical factors that give bean cell walls new polysaccharide arrangements. Rhamnogalacturonan I is dispersed throughout the entire cell wall and interacts with cellulose and hemicellulose fibres, resulting in a higher rate of pectic polysaccharide thermosolubility and, therefore, a shorter cooking time. Copyright © 2011 Society of Chemical Industry     

Utilization of Food Processing By-products as Dietary,Functional, and Novel Fiber: A Review

Fast growing food processing industry in most countries across the world, generates huge quantity of by-products, including pomace, hull, husk, pods, peel, shells, seeds, stems, stalks, bran, washings, pulp refuse, press cakes, etc., which have less use and create considerable environmental pollution. With growing interest in health promoting functional foods, the demand of natural bioactives has increased and exploration for new sources is on the way. Many of the food processing industrial by-products are rich sources of dietary, functional, and novel fibers. These by-products can be directly (or after certain modifications for isolation or purification of fiber) used for the manufacture of various foods, i.e. bread, buns, cake, pasta, noodles, biscuit, ice creams, yogurts, cheese, beverages, milk shakes, instant breakfasts, ice tea, juices, sports drinks, wine, powdered drink, fermented milk products, meat products and meat analogues, synthetic meat, etc. A comprehensive literature survey has been carried on this topic to give an overview in the field dietary fiber from food by-products. In this article, the developments in the definition of fiber, fiber classification, potential sources of dietary fibers in food processing by-products, their uses, functional properties, caloric content, energy values and the labelling regulations have been discussed.