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Query: UMLS:C0847097 (acidity)
 15,165 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Despite the relevance of volatile production for overall quality of apple (Malus x domestica Borkh.) fruit, only a few studies have focused on the effects of calcium treatments on this quality attribute. In this work, 'Fuji Kiku-8' apples were harvested at commercial maturity, dipped in calcium chloride (2%, w/v), stored at 1 degrees C and 92% relative humidity for 4 or 7 months under either air or ultralow oxygen (ULO; 1 kPa of O(2)/2 kPa of CO(2)), and placed subsequently at 20 degrees C. Ethylene production, standard quality parameters, emission of volatile compounds, and the activities of some related enzymes were assessed 7 days thereafter. Calcium concentration was higher in CaCl(2)-treated than in untreated fruit, suggesting that the treatment was effective in introducing calcium into the tissues. Higher calcium contents were concomitant with higher flesh firmness and titratable acidity after storage. Furthermore, calcium treatment led to increased production of volatiles in middle-term stored apples, probably arising from enhanced supply of precursors for ester production as a consequence of increased pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH) activities. After long-term storage, higher volatile emission might have arisen also from the enhancement of alcohol o-acyltransferase (AAT) activity, which was increased as a result of calcium treatment. In addition to storage period, the effects of calcium treatment were also partially dependent on storage atmosphere and more noticeable for fruit stored in air.
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PMID:Calcium dips enhance volatile emission of cold-stored 'Fuji Kiku-8' apples. 1944 74

This study developed a proteome reference map of Myrica rubra fruits at the green, pink and red stages during ripening using two-dimensional gel electrophoresis (2-DE). Forty-six differentially expressed proteins were detected in the gel, of which 43 were successfully identified by matrix-assisted laser desorption ionization time-of-flight/time-of-flight mass spectrometry and protein database searching. We found that malic enzyme related to the decrease of organic acid acidity was up-regulated. The high abundance of pyruvate decarboxylase and alcohol dehydrogenase may contribute to fruit peculiar fragrant characteristics. Phenylalanine ammonia-lyase, chalcone synthase 11, UDP-glucose:flavonoid 3-O-glucosyltransferase, and anthocyanidin synthase, enzymes involved in the anthocyanin metabolic pathway, were all up-regulated. The physiological data agree with fruit proteome results. These findings provided insights into the metabolic processes and regulatory mechanisms during Chinese bayberry fruit ripening.
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PMID:Functional analysis of differentially expressed proteins in Chinese bayberry (Myrica rubra Sieb. et Zucc.) fruits during ripening. 2621 36

Previous studies reported that the use of Metschnikowia pulcherrima in sequential culture fermentation with Saccharomyces cerevisiae mainly induced a reduction of volatile acidity in wine. The impact of the presence of this yeast on the metabolic pathway involved in pyruvate dehydrogenase (PDH) bypass and glycerol production in S. cerevisiae has never been investigated. In this work, we compared acetic acid and glycerol production kinetics between pure S. cerevisiae culture and its sequential culture with M. pulcherrima during alcoholic fermentation. In parallel, the expression levels of the principal genes involved in PDH bypass and glyceropyruvic fermentation in S. cerevisiae were investigated. A sequential culture of M. pulcherrima/S. cerevisiae at an inoculation ratio of 10:1 produced 40% less acetic acid than pure S. cerevisiae culture and led to the enhancement of glycerol content (12% higher). High expression levels of pyruvate decarboxylase PDC1 and PDC5, acetaldehyde dehydrogenase ALD6, alcohol dehydrogenase ADH1 and glycerol-3-phosphate dehydrogenase PDC1 genes during the first 3 days of fermentation in sequential culture conditions are highlighted. Despite the complexity of correlating gene expression levels to acetic acid formation kinetics, we demonstrate that the acetic acid production pathway is altered by sequential culture conditions. Moreover, we show for the first time that the entire acetic acid and glycerol metabolic pathway can be modulated in S. cerevisiae by the presence of M. pulcherrima at the beginning of fermentation.
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PMID:Metschnikowia pulcherrima Influences the Expression of Genes Involved in PDH Bypass and Glyceropyruvic Fermentation in Saccharomyces cerevisiae. 2870 1