| Popis: |
Considering the numerous beneficial effects on human health ascribed to phenolic compounds studies were performed to investigate the modification of the amount of phenols (total phenols, flavonoids and nonflavonoids) and composition (quercetin, kaempferol and specific phenolic acids) in apricot nectar cocktail after using the fruit semi-products for nectar production (frozen apricot and apple purees and orange concentrate). The content of HMF, total sugars, reducing sugars and sucrose were determined as well. Because the semi-products were obtained from the raw material of unknown chemical composition, the same parameters were determined in fresh apricot, apple and orange fruits, which were not used for semi-product preparation. The purpose of this analysis was to establish the phenol content and composition in fresh fruits and to compare them with those in semi-products used for investigation. Total phenols, flavonoids and nonflavonoids were determined by the Folin-Ciocalteu procedure and a profile of individual flavonoids, phenolic acids and HMF were analyzed by HPLC with Diode-Array detection. Luff Schoorl method was used for total sugars, reducing sugars and sucrose determinations. Other determinations included dry matter by drying at 105 oC and pH. Fresh fruits and semi-products (except for apricot puree) had more reducing sugars than sucrose. It was not so in nectar cocktail because of sucrose addition. Reducing sugars and phenolic compounds are responsible for browning reactions. Total phenols were significantly different in fresh fruits as compared to semi-products and apricot nectar cocktail. Fresh apple had the highest (608.04 mg/100 g dry matter) level of total phenol contents. The major phenolic compounds were present as nonflavonoids (phenolic acids). The content of flavonoids in all fruits was present in low amounts. The highest amount was found in fresh apricots (73.62 mg/100g of dry matter) and the lowest in the fresh oranges (19.31 mg/100g of dry matter). Generally, during the fruit processing in semi-products the total phenol contents after preservation by freezing and evaporation decreased in apple puree and orange concentrate, but not in apricot puree. The reason was probably the presence of carotenoide pigments known as inhibitors of phenol degradation and the use of freezing for the preservation of apricot puree. Nonflavonoid compounds were more stable than flavonoids. In apricot nectar cocktail relatively high level of total phenols (147.53 mg/100g of dry matter) was detected, among them 138.25 mg/100g of dry matter nonflavonoids and 9.28 mg/100g of dry matter flavonoids were found. Nonflavonoids in fresh fruits, semi-products and apricot nectar cocktail consist mainly of chlorogenic, caffeic, p-coumaric and ferulic acids. Chlorogenic acid was the major phenolic acid in all investigated samples. The highest concentration was found in apple and apple puree. Gallic acid was found only in fresh apricot in small amounts and the HMF was detected in all semi-products, with the highest level in apple puree. The major flavonoid found in all samples was quercetin with the highest concentration in fresh apricot. In orange concentrate quercetin was present only in traces. Kaempferol was detected in fresh apricot and in apricot puree, but in apricot juice it was present only in traces. |
