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.
"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). "
[Show abstract][Hide abstract] 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.
"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. "
[Show abstract][Hide abstract] 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.
"Coffee produced by the wet method has less body and higher acidity; it is also more aromatic than coffee produced by the dry method, resulting in a higher acceptance by consumers. It is currently accepted that the metabolic reactions in the coffee fruits that occur during different types of processing can affect the chemical composition of beans and thereby affect beverage quality (Bytof et al., 2005, 2007). There are few reports published that analyse the changes in the chemical composition of coffee beans in response to different postharvest treatment methods, and it is not fully understood which components are important for the differences in beverage quality (Knopp et al., 2005). "
[Show abstract][Hide abstract] ABSTRACT: Fresh coffee fruits were subjected to different types of postharvest processing. Intact fruits were processed using the dry method (DI), peeled fruits were processed using the semi-dry method (DP) and fruits were processed using the wet method (W). The extraction of polysaccharides from the seeds from the unprocessed and processed fruits indicated that arabinogalactans and (galacto)mannans were the main polysaccharides. Higher amounts of polysaccharides were extracted from processed coffee. Among the treatments, lower amounts of water-soluble galactomannans were obtained from coffee beans processed by the dry and wet methods. The polysaccharides obtained from beverages prepared using beans from DI, DP and W methods showed different yields, total sugar and protein contents. Galactomannans and AGPs were also present in the coffee beverages. Although differences were found in the chemical compositions, no differences were observed in the viscosity or surface tension of coffee beverages from the DI, DP and W methods.
International Journal of Food Science & Technology 09/2010; 45(10):2167 - 2175. DOI:10.1111/j.1365-2621.2010.02388.x · 1.38 Impact Factor
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