722 PB 438 FRUIT QUALITY OF STRAWBERRY GUAVA

Fruit quality of strawberry guava, yellow strawberry guava (Psidium cattleianum Sabine) and red strawberry guava (Psidium cattleianum Sabine var. luidium) was investigated. Fruit weight of yellow strawberry guava ranged from 7.9 to 39.2 g, and that of red strawberry guava ranged from 3.6 to 15.9 g. Yellow strawberry guava was round, and red strawberry guava was ovoid, in fruit shape. strawberry guava fruit had many hard seeds. Yellow and red strawberry guava contained 16 to 137 and 5 to 33 seeds per fruit. Seed of red strawberry guava was bigger than that of yellow strawberry guava. Sucrose, glucose, and fructose were contained in strawberry guava fruit. Sucrose, glucose, and fructose contents of yellow strawberry guava fruit were 6.69%, 3.61%, and 6.27%, respectively. Those of red strawberry guava fruit were 9.52%, 2.09%, and 3.39%, respectively. Strawberry guava fruit contained about 1% of titratable acidity. Total ascorbic and dehydro-ascorbic acid contents of yellow strawberry guava fruit were 57.9 mg/100ml and 41.6 mg/100ml, respectively. Those of red strawberry guava were 81.4 mg/100ml and 74.4 mg/100ml, respectively. Fruit quality of strawberry guava was suitable to eat freshly.

Ređuktone und Reduktonate, I Das Redoxpaar Dehydroascorbinsäure-Ascorbinsäure und ihre Anionen / Reductones and Reductonates, I The Redox Pair Dehydroascorbic Acid-Ascorbic Acid and Anions

On the basis of NMR spectroscopy (1H and 13C) it can be shown that in water, dimethylsulfoxide and p-dioxane only the tautomer 1 of L-ascorbic acid is found in a measurable amount. Upon formation of the mono-anion la deprotonation occurs on the hydroxyl group attached to C-3; in addition the hydroxyl group on C-2 is deprotonated in case of the di-anion 1b. Both anions do not open the lactone ring.After oxidation with iodine in aqueous solution only the dimer of dehydroascorbic acid is detected. This is hydrolized with a half-life of three hours to the monomeric dehydro ascorbic acid dihydrate 7. In dimethylsulfoxide the oxidation rate is decreased, and therefore the formation of the monomeric non-hydratized dehydroascorbic acid 10 can be monitored. This undergoes ringclosure relatively fast to give the half-ketal 13, the reaction of which via 14 leads to the optical active dimeric dehydroascorbic acid 6. The L-ascorbic acid acetonide 15 is oxidised by iodine to 16 which undergoes racemization via the enol 17 to give 18. This forms an equilibrium with compound 19.