The KlTrk1 gene encodes a low affinity transporter of the K+ uptake system in the budding yeast Kluyveromyces lactis

Potassium uptake in Saccharomyces cerevisiae is mediated by at least two proteins, known as Trk1p and Trk2p. Direct involvement in cation movements has been demonstrated for Trk1p, which is the high affinity transporter. S. cerevisiae cells also show low affinity potassium uptake, perhaps mediated by Trk2p. Mutants lacking Trk1p, lose high affinity system, but when grown with moderate potassium concentrations, Trk2p seems to replace it. Mutants lacking both proteins are viable but require at least 10 mM K(+) in the medium to sustain growth. Here we report the cloning and characterization of a gene from Kluyveromyces lactis encoding a homologue of these two proteins. KlTrkp is a 1070 amino acid peptide that shows, overall, higher homology with Trk2p than with Trk1p, and its disruption gives rise to cells with deficient potassium transport and with an increased K(+) requirement for normal growth. Determination of kinetic parameters in the K. lactis wild-type and Kltrk1Delta strains, as well as in Sctrk1Delta Sctrk2Delta S. cerevisiae cells expressing KlTrk1, indicated that this is a low affinity component of a major potassium uptake system in K. lactis.     

Phenolics and antioxidative activities in common beans (Phaseolus vulgaris L)

Six bean cultivars grown in southern Manitoba for 2 years were evaluated for variability in yield of millstreams and phenolic constituents. The ethanolic extract of bean cultivars and millstreams was screened for antioxidant activity using the β‐carotene‐linoleate and the 1, 1‐diphenyl‐2‐picrylhydrazyl (DPPH) in vitro model systems. Cultivar was the main source of variation for yield of millstreams, content of phenolic compounds and antioxidant activities. Phenolic compounds in cultivars varied from 3.3 to 16.6 mg catechin equivalent and from 0.15 to 0.32 mg cyanidin‐3‐glucoside equivalent g^?1 bean for total phenolic and anthocyanin contents, respectively. The bean cultivars exhibited antioxidant activity (AA) of 10–46% inhibition of lipid peroxidation in the linoleate and 0.4–1.3 trolox equivalent antioxidant capacities (TEAC) in the DPPH model systems. The hull millstream with maximum concentration of phenolic compounds exhibited the strongest antioxidant activity of 383 µM trolox equivalent g^?1 hull. Total phenolic content, alone or in combination with other phenolic constituents, is a potential candidate as a selection criterion for antioxidant activity in beans. Copyright © 2005 Society of Chemical Industry     

Influence of Pre-drying treatments on Quality and Safety of Sun-dried Tomatoes. Part II. Effects of Storage on Nutritional and Sensory Quality of Sun-dried Tomatoes Pretreated with Sulfur, Sodium Metbisulfite, or Salt

ABSTRACT Pre‐drying treatments have been found to improve the quality of stored sun‐dried tomatoes. Based on previous investigation (Part I), 5 specific pretreatments were chosen for effects on nutritional value, sensory quality, and safety before and after 3 mo of storage (25 °C and 30% to 34% relative humidity). These pretreatments included (1) direct gas sulfuring with 2.3 kg (5 lb) SO₂; (2) with 3.6 kg (8 lb) SO₂; (3) dipping in 10% salt for 5 min; (4) 8% sodium metabisulfite for 5 min; and (5) 8% sodium metabisulfite and 10% salt for 5 min. The use of SO₂ improved color, rehydration ratio, and minimized the loss of ascorbic acid and lycopene. Sodium metabisulfite dipped tomatoes had better rehydration ratio and color than gas sulfured sun‐dried tomatoes. Untrained consumers ranked gas sulfured tomatoes higher than sun‐dried tomatoes produced by dipping in either sodium metabisulfite alone or sodium metabisulfite plus salt.     

Fungal Inactivation by Mexican Oregano (Lippia berlandieri Schauer) Essential Oil Added to Amaranth,Chitosan, or Starch Edible Films

ABSTRACT: Edible films can incorporate antimicrobial agents to provide microbiological stability, since they can be used as carriers of a wide number of additives that can extend product shelf life and reduce the risk of pathogenic bacteria growth on food surfaces. Addition of antimicrobial agents to edible films offers advantages such as the use of low antimicrobial concentrations and low diffusion rates. The aim of this study was to evaluate inhibition of Aspergillus niger and Penicillium spp. by selected concentrations of Mexican oregano (Lippia berlandieri Schauer) essential oil added to amaranth, chitosan, or starch edible films. Oregano essential oil was characterized by gas chromatography-mass spectrometry (GC/MS) analysis. Amaranth, chitosan, and starch edible films were formulated with essential oil concentrations of 0%, 0.25%, 0.50%, 0.75%, 1%, 2%, and 4%. Mold radial growth was evaluated inoculating spores in 2 ways: edible films were placed over inoculated agar, Film/Inoculum mode (F/I), or the edible films were first placed in the agar and then films were inoculated, Inoculum/Film mode (I/F). The modified Gompertz model adequately described growth curves. There was no significant difference (P > 0.05) in growth parameters between the 2 modes of inoculation. Antifungal effectiveness of edible films was starch > chitosan > amaranth. In starch edible films, both studied molds were inhibited with 0.50% of essential oil. Edible films added with Mexican oregano essential oil could improve the quality of foods by controlling surface growth of molds.     

In vitro fermentability and antioxidant capacity of the indigestible fraction of cooked black beans (Phaseolus vulgaris L.), lentils (Lens culinaris L.) and chickpeas (Cicer arietinum L.)

BACKGROUND: Pulses represent an important source of protein, as well as digestible and indigestible carbohydrates. Little information is available on the indigestible carbohydrates and antioxidant capacity of legume seeds. The cooked seeds of three pulses (black bean, chickpea and lentil) were evaluated for their indigestible fraction (IF), polyphenols content, antioxidant capacity and in vitro fermentability, including short‐chain fatty acid production. RESULTS: The insoluble indigestible fraction (IIF) was higher than the soluble counterpart (soluble indigestible fraction, SIF). The SIF value was highest in black beans, while no difference was observed between chickpeas and lentils. Black beans and lentils had higher polyphenols content than chickpeas. The IF of black beans exhibited the lowest and chickpeas the highest associated polyphenols content. Condensed tannins were retained to some extent in the IF that exhibited significant antioxidant capacity. The total IF of the three pulses produced short chain fatty acids (SCFA) after 24 h of in vitro fermentation by human colonic microflora. IF from black bean and lentil were best substrates for the fermentative production of butyric acid. CONCLUSIONS: It is concluded that the IF of pulses might be an important source of bioactive compounds. Copyright © 2010 Society of Chemical Industry     

Physicochemical characteristics of starch from bread wheat (Triticum aestivum) with “yellow berry”

The physiological disorder of yellow berry (YB) in wheat is characterized by starchy or mealy spots in the grains, and it is present mainly in irrigated wheat crops. YB grains have characteristic low protein content. This disorder is a problem that has been increasing in bread and durum wheat in the northern part of Mexico. Limited availability of nitrogen is considered to be the main cause. Starch of normal and yellow berry wheat grains were analyzed and properties were compared. Starch of YB wheat grains had higher percent crystallinity, as demonstrated by X‐ray diffraction and DSC studies. Differences in pasting behavior were also observed. Starch from YB wheat grains had higher peak and set back viscosities. Starch granule size distribution as well as physicochemical properties indicates changes in composition or microstructure of starch granules of YB wheat grains.