Quality Evaluation Of Chinese Main Buckwheat Cultivars And Effect Of Processing On The Components And Health-relevant Functionality Of Buckwheat

Buckwheat (Fagopyrum esculentum), which is usually grouped together with cereals, is analternative crop belonging to the Polygonaceae family. Two main species of buckwheat are producedand consumed around the world: common buckwheat (Fagopyrum esculentum Moench) and tartarybuckwheat [Fagopyrum tataricum (L.) Gaench]. China is one of the largest producers of buckwheat inthe world, especially tartary buckwheat. The grain of buckwheat is highly nutritious due to high levelsof protein, starch, dietary fibre, some minerals, vitamins, flavonoids and other bioactive compounds.The paper mainly studies as follows:Thirty nine buckwheat cultivars were collected from China, of which twenty one were tartarybuckwheat and others were common buckwheat. Flour samples from these cultivars were analysed forcolour properties, nutritional composition,physicochemical properties of starch and flavonoid content.Buckwheat cultivars exhibited high variations for each of these parameters. The flour of commonbuckwheat showed a higher whiteness index than that of tartary buckwheat and contained very lowlevels of flavonoids. On average, the tartary buckwheat flour contained a higher level of ash (2.38%)and lower levels of total starch (70.22%), amylose (22.32%), resistant starch (17.66%) than the commonbuckwheat flour (2.17%,73.69%,23.01%,18.69%respectively)(P <0.05) whereas the contents ofproteins, fats and crude fibres of the tartary buckwheat flour were similar to those of commonbuckwheat flour. The granule size of buckwheat starch was2-6μm. The Mei-Hua-Shan tartarybuckwheat flour contained the highest level of total flavonoids and quercetin (22.74mg/g and2.38mg/g, respectively).The reflux extraction was adapted to extract the total polyphenols from common buckwheat bran.The effecting factors: ethanol concentration, extraction temperature, ratio of solid to liquid, extractiontime and No. of extraction times were investigated and optimized through an orthogonal experiment(L16(45)). The optimum technological parameters for extraction of total polyphenols were shown that:ethanol concentration65%, temperature70℃, ratio of solid to liquid1:8, extraction time1.5h, No. ofextraction3times.This study focused on the evaluation of changes in phytochemical compositions, antioxidant andα-glucosidase inhibitory activities during the processing of tartary buckwheat tea. Soak-treating tartarybuckwheat significantly decreased the contents of total starch and rutin, whereas significantly increasedthe contents of quercetin, kaempferol, total flavonoid, and total phenolic compounds. In steam-treatingsoaked tartary buckwheat for40–60min, the contents of total starch, protein, crude fat, isoquercitrin,quercetin, kaempferol, total flavonoid and total phenolic compounds significantly decreased, whereasthe content of rutin significantly increased. The reaction of rutin degrading might be catalyzed insoaking processing, and a catalytic reverse shift reaction of rutin-synthesizing might take place insteaming processing. The process of drying and roasting significantly decreased the contents of total starch, rutin, total flavonoid, and total phenolic compounds. The total phenolic content of collectedtartary buckwheat materials positively correlated with the antioxidant and α-glucosidase inhibitionactivities.The aims of present study were identification and quantification of the aroma compounds of tartarybuckwheat tea. The analyses were performed by gas chromatography-mass spectrometry (GC-MS) after3different isolation techniques. Seventy-seven compounds were identified. Among these compounds,35were quantified by available standards. The compoundswith a high probability of contribution to thetartary buckwheat tea aroma (OAV≥10) were as follows:2,5-dimethyl-4-hydroxy-3(2H)-furanone,nonanal,2,3-diethyl-5-methylpyrazine, benzeneacetaldehyde, maltol,2,5-dimethylpyrazine,2-ethyl-5-methylpyrazine, trimethylpyrazine. Some nutritional and bioactive compounds were alsoidentified in this study, such as linoleic acid, niacin, vanillic acid,7-hydroxycoumarin, butylatedhydroxytoluene.