Influence of processing on the generation of γ-aminobutyric acid in green coffee beans. Eur Food Res Technol
German Research Centre for Food Chemistry, Freysing, Bavaria, GermanyEuropean Food Research and Technology (Impact Factor: 1.56). 01/2005; 220(3):245-250. DOI: 10.1007/s00217-004-1033-z
A determination of the concentrations of free amino acids in differently processed green coffees indicated the nonprotein amino acid -aminobutyric acid (GABA), a well-known plant stress metabolite, to be present in raw coffee beans (Coffea arabica L.) in significantly varying amounts. The GABA content of unwashed Arabica beans (green coffee produced by the dry processing method) was always markedly higher than that of washed Arabicas (wet processing method) as well as that of untreated seeds. This result underlined the assumption that during postharvest treatment a significant metabolism occurs within coffee seeds. A putative relation between drought stress of the coffee seeds and postharvest treatment methods is discussed. The GABA content of green coffee beans may serve as a potent tool to characterize the type of postharvest treatment applied in coffee processing.
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- "This metabolism becomes evident by the conversion of glutamic acid into γ-aminobutyric acid mediated by an enzymatic α-decarboxylation. The reaction is related to a physiological drought stress situation and is specific to the mode of processing applied (Bytof et al., 2005). Such alterations in the pool of free amino acids — components which are considered as essential precursors of flavor and color of the coffee brew (Homma, 2002) — may be suitable to explain some of the sensorial differences between ‗‗washed‖ and ‗‗unwashed‖ coffees. "
ABSTRACT: Coffee has been for decades the most commercialized food product and most widely consumed beverage in the world, with over 600 billion cups served per year. Before coffee cherries can be traded and processed into a final industrial product, they have to undergo postharvest processing on farms, which have a direct impact on the cost and quality of a coffee. Three different methods can be used for transforming the coffee cherries into beans, know as wet, dry and semi-dry methods. In all these processing methods, a spontaneous fermentation is carried out in order to eliminate any mucilage still stuck to the beans and helps improve beverage flavor by microbial metabolites. The microorganisms responsible for the fermentation (e.g., yeasts and lactic acid bacteria) can play a number of roles, such as degradation of mucilage (pectinolytic activity), inhibition of mycotoxin-producing fungi growth and production of flavor-active components. The use of starter cultures (mainly yeast strains) has emerged in recent years as a promising alternative to control the fermentation process and to promote quality development of coffee product. However, scarce information is still available about the effects of controlled starter cultures in coffee fermentation performance and bean quality, making it impossible to use this technology in actual field conditions. A broader knowledge about the ecology, biochemistry and molecular biology could facilitate the understanding and application of starter cultures for coffee fermentation process. This review provides a comprehensive coverage of these issues, while pointing out new directions for exploiting starter cultures in coffee processing.
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- "Vidal-Valverde et al. (2002) found that GABA contents is influenced by germination time, temperature, pH, and chemical inhibitors through are regulation of the DAO activity in fava beans. Bytof et al. (2005) also reported that germination in the presence of light for lentils, and in darkness for peas can increase the GABA content. Other studies have also showed the biotransformation of cereal proteins to GABA by LAB in sourdough (Stromeck, Hu, Chen, & Gä nzle, 2011). "
ABSTRACT: The effects of pre-processes (immersing, germinating, and cold shock) and fermentation conditions of adzuki beans on γ-aminobutyric acid (GABA) accumulation using mixed cultures of Lactococcus lactis and Lactobacillus rhamnosus were investigated in this study. Among the preprocessing methods, cold shock treatment resulted in the highest observed GABA content (201.2 mg/100 g); a 150-fold increase compared to the non-treated adzuki beans. The LAB strains grew rapidly in cold-treated adzuki bean substrates and reached 108 cfu/ml after 24 h of fermentation at 30 °C. After optimization, the GABA yield reached 68.2 mg/100 ml; a 20-fold increase compared to the non-fermentation yield. The viable cell counts of LAB remained above 108 cfu/ml after 28 days of storage at 4 °C. Our results suggest that the combination of cold shock pretreatment and fermentation by LAB may be used for the preparation of adzuki beans with high GABA content, which can then be used as a natural resource of functional foods.
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- "Data evaluation was performed by the second derivative (XSDM) method. GABA was quantified by HPLC according to Bytof et al. (2005). – it could impact the overall performance in synthesis, translocation and accumulation of the relevant compounds. "
ABSTRACT: When medicinal plants are grown under semi-arid conditions, they generally reveal significantly higher concentrations of relevant natural products than identical plants of the same species, which however are cultivated in moderate climates. Up to now, only limited information on this well-known phenomenon is available. In this treatise, corresponding data are compiled and relevant aspects are discussed. It becomes obvious that drought stress-related metabolic changes are responsible for the higher natural product accumulation in plants grown in semi-arid regions. The corresponding plant physiological and biochemical background is outlined as follows: Due to limited water supply and much higher light intensities, the plants suffer drought stress. The related water shortage leads to stomata closure and as a result the uptake of CO2 is markedly decreased. Accordingly, the consumption of reduction equivalents (NADPH+H+) for the CO2-fixation via Calvin cycle declines considerably, generating a massive oversupply of NADPH+H+. As a consequence, metabolic processes are pushed towards the synthesis of highly reduced compounds like isoprenoids, phenols or alkaloids. Based on these coherences, impulses for novel practical approaches for enhancing the product quality by deliberately applying drought stress during the cultivation of medicinal plants are given. However, as drought stress concomitantly leads to massive reductions in biomass production, special emphasis is put on the interference of these stress-related effects.
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