No abstract

Chemical composition and antioxidant activity of juice from immature and mature acerola and of concentrated juice from immature acerola were determined. Tartaric, malic and citric acids and a high content of ascorbic acid were found in all the juices. Vitamin C contents were 4.80, 1.90 and 0.97 g/100 g for the concentrated immature, the immature, and the mature acerola juices respectively. The total phenol contents decreased during ripening, from 3.8 mg of catechin/g for immature acerola juice to 1.4 mg of catechin/g for mature acerola juice. The concentrated immature juice had a content of 9.2 mg of catechin/g of juice. Catechin, gallic acid, coumaric acid, syringic acid, caffeic acid and ferrulic acid were detected in immature acerola juice by HPLC analysis whereas mature acerola juice showed only one predominant peak with a retention time similar to that of ferrulic acid. The concentrated juice from immature acerola reduced the oxidation of methyl linoleate by 57.2% while the juice from immature acerola reduced the oxidation by 28.1%. These results stated that the antioxidant potential of the acerola juice depended on its content of phenolic compounds and the vitamin C.

Kinetic studies on the degradation of vitamin C and nonenzymatic browning of green West Indian cherry juice and synthetic ascorbic acid, encapsulated in maltodextrin DE20 and a mixture of this with gum arabic, were carried out at different temperatures (15, 25, 35 and 45 • C). Vitamin C degradation followed the first-order and nonenzymatic browning a zero-order kinetic model. At higher storage temperatures the formulation containing a mixture of maltodextrin and gum arabic (3:1) was the most effective for vitamin C protection. An increase in storage temperature showed a greater impact on the degradation of synthetic vitamin C than on that of the green West Indian cherry juice. These differences could be due to the presence of phenolic compounds with antioxidant activity, protecting the vitamin C.

Passion fruit juice, pure and sucrose sweetened (1:1, w:v), was frozen and stored for 8 months in freezers. The effect of storage time and sucrose addition on physicochemical properties of the juices was evaluated, in the fresh juice, and then every two months in the stored samples. Concentration of soluble solids, organic acids, total and reducing sugars and ascorbic acid, as well as pH were not affected by storage time. Initially sucrose addition modified the juice color, but not during storage time, while the natural juice became more yellow during storage. β -carotene content decreased as a function of storage time, 51.3 % in the pure juice and 29.7 % in the sweetened juice.
Suco de maracujá, puro ou previamente adoçado com sacarose, 1:1 (p:v), foi congelado e armazenado por 8 meses em congeladores com temperatura de -18°C. O efeito de tempo de armazenamento e adição de sacarose sobre propriedades físico-químicas foi avalida inicialmente no suco fresco e a cada dois meses nas amostras congeladas. Concentrações de sólidos solúveis, ácidos orgânicos, açúcares totais e redutores e ácido ascórbico, assim como pH, não foram afetados por tempo de armazenamento. Inicialmente a adição de sacarose alterou a cor do suco, mas esta se manteve durante o armazenamento, enquanto o suco natural alterou a cor para amarelo durante o armazenamento. Concentração de β-caroteno diminuiu em função do tempo de armazenamento, 51,3% no suco puro e 29,7% no suco previamente adoçado

sugestões e trocas de idéias.A todos os funcionários do DEPAN, em especial ao Chico, Beth, Eliana e Gustavo, pela colaboração e amizade.