Ming-Ho Yu

Quality and nutritional composition of tomato fruit as influenced by certain biochemical and physiological changes

The chemical contituents are concerned in the quality of tomato fruit in respect to color, texture, flavor, nutritive value, and wholesomeness. In general, high sugar contents, redness of color, and firm texture are associated with prominence of rich flavor. Biochemical changes as influenced by growth, maturation, and environment of tomato fruit are discussed.

The formation of delta‐Aminolevulinate a precursor of chlorophyll, in barley and the role of iron

Abstract Chlorophyll formation in higher plants is light dependent. Light directly affects the formation of 6‐aminolevulinic acid (ALA) and the conversion of protochlorophyll to chlorophyll. Various chelators that form especially stable compounds with ferrous iron reduce the formation of ALA in etiolated barley leaves. Barley grown under iron stress has little capacity to form ALA unless supplemental iron is added. Chelated iron and FeSO4 are much more effective in restoring ALA formation than FeCl3. Added organic compounds (citrate, α‐ketoglutarate and glucose) also stimulated ALA synthesis. The role of iron in ALA and chlorophyll synthesis is discussed.

Fluorosis in black-tailed deer.

Marked dental disfigurement and abnormal tooth wear patterns were observed in black-tailed deer (Odocoileus hemionus columbianus) taken from an area near an industrial fluoride source in northwestern Washington. Fluoride levels in the bones of these deer were from 10 to 35 times higher than levels in the bones of normal animals. These levels are similar to those associated with fluorosis of cattle.

Precursors of volatile components in tomato fruit—II : Enzymatic production of carbonyl compounds

Abstract Crude enzyme preparations from fresh tomatoes in the presence of certain amino acids are capable of producing carbonyl compounds. The activities of the enzyme extracts from field-grown tomatoes were generally higher than those grown in greenhouses. Enzyme activities increased with the maturity of the fruit, whereas the protein content of the extracts tended to decrease. Three amino acids used as substrates gave distinctive responses with the enzyme and the activity in general appears to be associated with the insoluble part of the preparations.

Precursors of volatile components in tomato fruit—I. : Compositional Changes during development

Abstract The composition of tomato fruit at nine different stages of maturity was studied. The dry matter content decreased gradually, whereas the alcohol-soluble material and non-protein nitrogen increased with ripening. Total nitrogen decreased up to the large green stage and then increased during ripening. Starch accumulated until nearly the large green stage and then diminished rapidly. Of the two components of starch, amylose decreased much faster than amylopectin, and the ratios of amylopectin and amylose thus increased during ripening. Among the amino acids, glutamic acid was present in an exceptionally high concentration, and its concentration doubled during ripening. A concomitant decrease in the concentration of several other amino acids was noted. The possibility of amino acids serving as precursors for the synthesis of volatile aroma components in tomato is discussed.

Gas chromatography of the field-, glass- Greenhouse-grown, and artificially ripened tomatoes.: Lycopersicon esculentum mill.

Abstract Fifteen distinct peaks were resolved from red-ripe tomato flavor extract by gas Chromatographic techniques. Except isobutanol, n -hexanol, and n -hexanal, concentrations of the volatile components in the field-grown tomatoes were higher than those in the greenhouse-grown tomatoes. Artificially ripened tomatoes contained less volatile components.

Precursors of volatile components in tomato fruit-III. Enzymatic reaction products

Abstract The volatile components produced by enzyme extracts from tomato fruit using amino acid substrates were analysed by gas and thin-layer chromatography. Alanine, leucine, and valine were among the best substrates. Extracts from red-ripe tomatoes were more active than those from green fruit. The products differed somewhat with each preparation and with the particular substrate used. Propanal was present in most reaction products especially when alanine was used as substrate. With enzymes from red-ripe fruit, alanine gave mainly carbonyl compounds while leucine and valine gave mainly alcohols. Mixed amino acids sometimes resulted in new volatile components. The mechanism appears to involve transamination.

Conversion of l-leucine to certain keto acids by a tomato enzyme preparation

Abstract An enzyme preparation from fresh tomato fruit catalyzed the degradation of l -leucine. The reaction products were separated as their 2,4-dinitrophenylhydrazones and analyzed by TLC. α-Ketoisocaproic acid, the keto acid corresponding to l -leucine, was identified. The conversion was confirmed by studies with l -leucine-U- 14 C as substrate. Enzyme activity was found to occur predominantly in the supernatant fraction and to decrease with ripening of fruit.

Formation of delta‐aminolevulinic acid in etiolated and iron‐stressed barley

Abstract The effects of several Krebs Cycle metabolites and related compounds and iron on the formation of 6‐aminolevulinic acid (ALA) in etiolated and iron‐stressed barley leaves were studied. Citrate, in addition to glutamate and α‐ketoglutarate, was found to be effective in enhancing the accumulation of ALA. Succinate was relatively poorly utilized. Ascorbate showed an inhibitory effect. Whereas added FeSO4 depressed ALA content in the etiolated leaves, it enhanced the level in iron‐stressed tissue. Fluoroacetate at 10 mM exhibited a strong inhibitory effect on ALA formation. The activity of aconitase in iron‐stressed plants was increased by treatment of the leaf tissue with iron.

α-Alanine aminotransferase from tomato fruit.

Abstract The α-alanine aminotransferase, l -alanine:2-oxoglutarate aminotransferase EC 2.6.1.2, has been demonstrated in tomato fruit. The enzyme was found in both the supernatant and the mitochondrial preparations; under the experimental conditions used, activity in the mitochondria decreased with development of fruit. The α-alanine aminotransferase was more active than leucine aminotransferase from the same source.