ABSTRACT Understanding the role of photosynthesis in the holoparasitic genus Cuscuta may give insights into the biology and evolution of these plants. We hypothesised that light irradiance on the node of C. racemosa is important for sustaining the growth of the new shoot through photosynthesis. We blocked light irradiance on the node of detached twigs of C. racemosa for one week and measured twig fresh and dry weight, shoot length and photosynthetic pigment content. Even though fresh and dry weight did not differ between non-irradiated and irradiated twigs, the shoots of non-irradiated nodes were significantly shorter. The non-irradiated plants showed higher amounts of chlorophyll a, b, and lycopene, and a lower concentration of β-carotene. Furthermore, the chlorophyll a/b ratio was lower than that of the control (irradiated) plants. Beyond corroborating our hypothesis, our results suggest that, when light is blocked on the node of C. racemosa, the holoparasite responds in a way similar to that of autotrophic plants under shaded conditions. Our findings suggest a new and previously unacknowledged role for the node of C. racemosa, which would be supporting shoot elongation through photosynthesis.

Resumo O Brasil apresenta grande variedade de frutas nativas que têm despertado interesse comercial, a exemplo do araçá. Nesse sentido, muitas pesquisas têm buscado alternativas que permitam a disponibilidade do fruto pós-colheita, considerando que a perecibilidade é um fator limitante para sua comercialização. O processo de congelamento é uma alternativa importante no sentido de disponibilizar esses frutos por mais tempo no mercado. O uso de ácido L-ascórbico é um potente agente protetivo na estabilidade de compostos bioativos em polpas de frutas. O estudo teve como objetivo avaliar compostos potencialmente bioativos, presentes em polpas de araçás-vermelho e amarelo adicionadas de ácido L-ascórbico (1 % m/m) e verificar sua ação na retenção destes compostos em sua atividade antioxidante durante o armazenamento congelado (-20 ± 2ºC). Nas polpas, foram analisados: atividade antioxidante pela captura dos radicais DPPH° e ABTS°, fenóis, antocianinas e carotenoides totais. O ácido L-ascórbico influencia positivamente na retenção dos compostos bioativos (fenóis totais, antocianinas totais e carotenoides totais) em polpas de araçás-vermelho e amarelo, durante 120 dias de armazenamento congelado (-20 ± 2ºC).

Abstract Brazil presents a great variety of native fruits, which have aroused commercial interest, such as the strawberry guava. In this sense, many researches have looked for alternatives that allow postharvest availability of fruits, considering that perishability is a limiting factor for its commercialization. The freezing process is an important alternative in the sense of making these fruits available for longer on the market. The use of L-ascorbic acid is a potent protective agent in the stability of bioactive compounds in fruit pulps. The objective of this study was to evaluate potentially bioactive compounds present in red and yellow strawberry guava pulps added with L-ascorbic acid (1% m / m) and verify its effect on retention of these compounds and in its antioxidant activity during the frozen storage (-20 ± 2ºC). In the pulps were analyzed: antioxidant activity by the capture of the DPPH° and ABTS° radicals, phenols, anthocyanins and total carotenoids. L-ascorbic acid positively influences the retention of bioactive compounds (total phenols, total anthocyanins and total carotenoids) in red and yellow strawberry guava pulps during 120 days of frozen storage (-20 ± 2 ºC).

RESUMO Objetivou-se elaborar geleias de araçá vermelho do tipo convencional (com adição de sacarose) e sem adição de açúcares e avaliar a composição físico-química e teores de compostos bioativos presentes nas mesmas. Foram elaboradas quatro formulações de geleias: convencional com adição de sacarose (F1); com adição de aspartame (F2); com adição de sacarina e ciclamato (F3); com adição de acessulfame e sucralose (F4). Foram realizadas análises físico-químicas de pH, acidez total titulável, sólidos solúveis totais, cinzas, proteínas, lipídios, umidade, carboidratos, valor calórico, luminosidade, tonalidade de cor, fenóis totais, antocianinas totais, carotenoides totais, ácido ascórbico e atividade antioxidante pela captura dos radicais DPPH e ABTS. As geleias convencional e sem adição de açúcares não diferiram para fenóis totais, antocianinas totais e ácido ascórbico. Contudo, o processamento exerceu influência significativa (p=0,05) sobre carotenóides totais e atividade antioxidante. É viável a utilização de araçá vermelho para elaboração de geleias convencional e sem adição de açúcar. Os produtos, contudo, apresentam diferença significativa quanto aos teores de carotenóides, sendo os maiores teores destes e maior atividade antioxidante nas geleias processadas sem adição de açúcares.

ABSTRACT This study aimed to prepare jellies of conventional type of red strawberry guava (with added sucrose) and no added sugar and evaluate the physical and chemical composition and content of bioactive compounds in them. Four jellies formulations were prepared: conventional with addition of sucrose (F1), aspartame (F2), saccharin and cyclamate (F3), acesulfame and sucralose (F4). Physicochemical analysis of pH were carried out, as well as analysis of titratable acidity, total soluble solids, ashes, proteins, lipids, moisture, carbohydrates, calories, lightness, color tone, total phenols, anthocyanins, carotenoids, ascorbic acid and antioxidant activity, by the capture of DPPH and ABTS radicals. Conventional and no added sugars jellies did not differ for total phenols, total anthocyanins and ascorbic acid. However, processing exerted significant influence (p=0.05) on total carotenoids and antioxidant activity. It is feasible to use red strawberry guava for the preparation of conventional and no added sugar jellies. The products, however, show a significant difference in carotenoids content, with the highest content of these and higher antioxidant activity in processed jellies without sugars addition.