Avaliação da estabilidade da capacidade antioxidante e de parâmetros físico-químicos de néctares de frutas caseiros / Assessment of the antioxidant capacity and of the physicalchemicals parameters stability in homemade fruit nectars

Este estudo avaliou a capacidade antioxidante e os indicadores físico-químicos de néctares caseiros de laranja, manga e maracujá, mantidos sob refrigeração (5 ± 2 o C) por 24 horas. Os néctares foram preparados em laboratório e mantidos sob refrigeração, simulando as condições domésticas. As análises foram realizadas após o preparo (T0) e durante o acondicionamento sob refrigeração (1 h, 4 h e 24 h). Os sólidos solúveis, pH e cor foram determinados respectivamente por refratometria, potenciometria e colorimetria. Carotenoides e ácido ascórbico foram analisados por cromatografia líquida de alta eficiência; a concentração de compostos fenólicos foi determinada utilizando-se o reagente de Folin Ciocalteau e a atividade antioxidante pelo teste do DPPH. Ácido ascórbico, β-caroteno e compostos fenólicos foram identificados em todos os néctares. Foram encontrados α-caroteno e β-criptoxantina no néctar de laranja e licopeno no néctar de manga. Durante 24 horas de refrigeração, os compostos analisados e a atividade antioxidante mantiveram-se estáveis. De forma geral, os parâmetros físico-químicos também se mantiveram estáveis durante o período avaliado. Em conclusão, sob as condições utilizadas no presente estudo, os néctares não apresentaram alteração da capacidade antioxidante, podendo ser considerados fontes de carotenoides e vitamina C, mesmo se consumidos após 24 horas de preparo.

The objective of the study was to evaluate the antioxidant capacity and the physical-chemical indicators of homemade nectars of orange, mango and passion fruit, kept under refrigeration (5 ± 2 °C) for 24 hours. The nectars were prepared in laboratory and kept under refrigeration simulating the domestic conditions. The samples analyses were performed after their preparations (T0) and during the refrigerated storage (1 h, 4 h and 24 h). Soluble solids, pH and color were determined by refractometry, colorimetry and potentiometry, respectively. Carotenoids and ascorbic acid were analyzed by high performance liquid chromatography, the concentration of phenolic compounds were determined by using Folin Ciocalteau reagent, and the antioxidant activity by the DPPH test. Ascorbic acid, β-carotene and phenolic compounds were identified in all of the analyzed nectars samples. The α-carotene and β-cryptoxanthin were found in orange nectar and the lycopene in mango nectar samples. During the refrigeration for 24 hours, the analyzed compounds and the antioxidant activity remained stable. In general, the physical-chemicals parameters also remained stable during the storage for 24 hours. In conclusion, under the conditions used in this study, the nectars might be considered as antioxidant sources, even if consumed after being prepared 24 hours before.

Phenolic profiles of nectar and honey of Quillaja saponaria Mol. (Quillajaceae) as potential chemical markers

Quillaja saponaria Mol. (Quillajaceae) is one of the most important melliferous species in Chile, mainly as a source of monofloral honey. Honey made by A. mellifera presents biological activity against pathogens and antioxidant capacity associated with the presence of phenolic compounds deriving from the nectar, as a result of bee honey foraging. The aim of this study was to identify and quantify the phenolic compounds from the floral nectar of Q. saponaria and the honey made in apiaries in the central zone, and compare the composition of the chromatographic profiles of nectar and honey to known phenolic compounds. The results obtained by HPLC-DAD (high-performance liquid chromatography with diode-array detection) showed a similar profile of phenolic compounds, in which gallic acid, myricetin, rutin, quercetin and naringenin were identified. The phenolic compounds detected could be used as a reference for future studies for determining potential chemical markers of this honey, complementing the present identification of honeys by determining their botanical origin. The identification of bioindicators of the floral origins for honey of this species could provide added value to honey commercialization by certifying the botanical origin of their chemical features and biological attributes.

Effect of processing and storage time on the vitamin C and lycopene contents of nectar of pink guava (Psidium guajava L.) / Efecto del procesamiento y tiempo de almacenamiento en el contenido de vitamina C y licopeno en néctar de guayaba rosada (Psidium guajava L.)

In this study, the effect of processing and storage time on the vitamin C and lycopene contents was evaluated. Guavas were washed, cut in quarters, blanched, pulped and the pulp pasteurized. The pulp was used for the production of nectar: guava pulp, sugar and water were mixed in 5:3:12 proportions, and the mixture was pasteurized, poured while hot into 125 mL glass jars, and cooled rapidly to 25°C. The production of nectar from fresh guava reduced vitamin C, lycopene and titratable acidity, by contrast soluble solid and pH increased significant. Vitamin C content from 168.9 to 62.3 mg/(100 g fresh weight), and lycopene content from 3.55 to 1.35 mg/(100 g fresh weight) (p < 0.001 in both cases. After 240 days at 10.0 ± 2°C, no further statistically significant change in lycopene and soluble solid content was observed (p > 0.05). Storage time did affect vitamin C, pH, and titratable acidity content, vitamin C content fell by 89.3% to 6.67 mg/(100 g fresh weight) (p < 0.001). Based on this study, guava nectar storage at 10 ° C retained 46% of the content of vitamin C for 120 days.

En este estudio, el efecto del procesamiento y el tiempo de almacenamiento en el contenido de vitamina C y licopeno fueron evaluados. Las guayabas fueron lavadas, cortadas en cuartos, escaldadas, despulpadas y la pulpa pasteurizada. La pulpa se utilizó en la producción del néctar: pulpa de guayaba, azúcar y agua se mezclaron en la proporción de 5:3:12, y la mezcla se pasteurizo, vertido en caliente en frascos de vidrio 125 ml, y se enfrío rápidamente a 25°C. La producción de néctar de guayaba fresca reduce la vitamina C, licopeno y la acidez titulable, en contraste los sólidos solubles y el pH se incrementan significativamente. El contenido de vitamina C de 168,9 a 62,3 mg/100 g de peso fresco, y el contenido de licopeno de 3,55 a 1,35 mg/100 de peso fresco (p < 0,001 en ambos casos). Después de 240 días a 10,0 ± 2ºC no se observó cambios estadísticamente significativos en el contenido del licopeno (p > 0,05). El tiempo de almacenamiento afectó el contenido de vitamina C, el pH y acidez titulable, el contenido de vitamina C se redujo en un 89,3% a 6,67 mg/100 g de peso fresco (p < 0,001). En base a este estudio, el almacenamiento de néctar de guayaba a 10°C, conserva el 46% del contenido de vitamina C durante 120 días.