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, Germany
European Food Research and Technology (Impact Factor: 1.39). 01/2005; 220(3):245-250. DOI: 10.1007/s00217-004-1033-z

ABSTRACT 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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    • "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). "
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    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.
    Journal of Functional Foods 06/2013; 5(3):1108-1115. DOI:10.1016/j.jff.2013.03.006 · 4.48 Impact Factor
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    • "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). "
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    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 · 1.35 Impact Factor
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    • "These metabolic reactions, which are mainly due to germination processes (Bytof et al., 2007) as well as stress metabolism, are responsible for significant changes in the composition of substances present in the coffee beans and thus for their quality (Bytof, Knopp, Schieberle, Teutsch, & Selmar, 2005). It could be shown that quantity and composition of soluble, low molecular weight carbohydrates, amino acids and stress metabolites i.e. c-amino butyric acid (GABA), respectively, strongly depend on the characteristic conditions of the green coffee processing (Bucheli, Meyer, Pasquier, & Locher, 1996; Bytof et al., 2005; Knopp, Bytof, & Selmar, 2006). Although various studies on the influence of the overall processing have been carried out, until recently only limited data on the distinctive influence of the drying procedure on wet processed coffees has been available (for review see Bytof et al., 2007; Selmar & Bytof, 2007). "
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    ABSTRACT: When wet processed coffee beans are dried, the resulting decrease in the water potential induces various metabolic responses. This study was aimed at elucidating the impact of these reactions on the composition of sugars, representing potential aroma precursors. Wet processed green coffees were dried under defined conditions, and the relevant sugars were analysed. Special emphasis was put on the influence of the drying regime, i.e. continuous dryings and such interrupted by pauses in order to mimic sun dryings.The contents of fructose and glucose decreased significantly within the first day of drying. This diminution for the first time proves that the lower contents of glucose and fructose generally present in wet processed coffee beans in comparison to dry processed ones are – at least in part – due to metabolic processes and are not related to the leaching of sugars into the process water in the course of wet processing.
    Food Chemistry 03/2010; 119(2):500-504. DOI:10.1016/j.foodchem.2009.06.048 · 3.26 Impact Factor
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