The maturity of two selections of soursop (G1 and G2) from Nayarit, Mexico, was evaluated under environmental conditions at 22°C and refrigeration at 15°C stored for 6 and 8 days, respectively. Maximum CO2and ethylene values were present on the fifth and sixth day. The fruits exposed at 15°C had a significantly lower weight loss (5%) and showed no chilling injury. The firmness of two selections decreased more than 90%. The concentration of TSS increased to 5.3 to 15°Brix, and the titratable acidity was higher for fruit stored at 22°C. The highest concentration of phenols was recorded on the fourth day of storage at 22°C. The enzymatic activity of PPO was increased from physiological ripening to consumption ripening for both treatments. The two selections stored at 22°C registered the highest level of PME activity at ripeness. Shelf life was increased by up to 8 days (4 days at 15°C plus 4 days at 22°C) without causing chilling injury or alterations in the ripening process of the fruits. No significant differences were observed between the two selections evaluated; postharvest handling was considered to be similar; however, it would be advisable to evaluate other technologies combined with refrigeration.

Nayarit es el principal productor de guanábana (Annona muricata L.) a nivel mundial; sin embargo, no se reconocen variedades o ecotipos presentes en la entidad, la mayoría de la producción se realiza en árboles a pie franco. Así, se presentan resultados de una investigación preliminar sobre la caracterización de frutos de guanábana (Annona muricata L.) de Tepic, Nayarit. Se seleccionaron 13 árboles de ocho años de edad, de los cuales se cosecharon de cuatro a siete frutos entre junio y julio de 2014. La masa del fruto en la población varió entre 837.8 y 2513 g, la proporción promedio de pulpa, cascara y semilla fue de 71, 20.5 y 8.5%, respectivamente, en la población. Los frutos fueron elípticos en promedio, con un contenido de semillas entre 19 y 311. El color de la epidermis del fruto fue verde opaca y poco luminosa (h= 151.7 - 164.9, C*= 9.4-21.4; L*= 30.2 -45.8), la firmeza fue en promedio de 7.3 N, los sólidos solubles totales entre 7.1 y 14 °Brix, la acidez titulable promedio fue de 0.7 % y el pH de 3.6. El análisis de conglomerados formó 4 grupos. El grupo cuatro presentó el menor número de semillas (41) y mayor cantidad de SST (13.2 oBrix). Las variables masa, dimensiones y color de la cascara ayudaron a la separación de los grupos. Se determinó variabilidad en guanábana con potencial para obtener frutos para el mercado en fresco e industrial; así como para propagación de la especie.

The changes in concentration of vitamin C, enzymatic and antioxidant activity during the ripening of two soursop selections (G1 and G2) at room temperature (22 ºC) and refrigeration (15 ºC) with an HR 85% were evaluated. The content of soluble protein, the activity of catalase (CAT), superoxide dismutase (SOD), peroxidase (POD), the concentration of vitamin C, as well as the antioxidant activity was evaluated by DPPH, ABTS and FRAP methods. The initial soluble protein concentration of the G1 and G2 selections diminished at 22 and 15 °C during ripening. Fruits stored at 22 °C showed the highest CAT activity. The maximum activity of SOD was recorded on the sixth and fourth day in fruits stored at 22 and 15 ºC, respectively. Fruits stored at 22 °C recorded the highest amount of vitamin C. Fruits stored at 22 and 15 ºC showed the highest antioxidant activity on the fourth day. The fruits stored at 15 ºC was able to increase the shelf life up to 8 days without affecting the ripening process. Therefore, the enzymatic and antioxidant activity has an important role in the possible alteration that the fruit might suffer during its fruit ripening.

ResumenEl sistema poscosecha de los frutos de guanábana (Annona muricata L.) aún no está desarrollado completamente, por lo que existen diversos problemas durante el manejo de los frutos. El ablandamiento acelerado, durante el almacenamiento postcosecha, y su comercialización es un problema constante y de suma importancia. Los frutos de guanábana son del tipo climatérico, caracterizándose por su alta tasa de respiración y producción de etileno, aunado a una actividad enzimática alta y su sensibilidad al frío. Los periodos prolongados de almacenamiento aun no son posibles, debido principalmente a la alta susceptibilidad al daño por frio. La información científica al respecto es aun limitada y dispersa y aunque se ha realizado investigación al respecto, ésta ha sido insuficiente. En este documento se hace una recopilación de las investigaciones más importantes, especialmente en las generalidades del fruto, la respiración, producción de etileno, cambios de maduración, actividad enzimática y técnicas de almacenamiento postcosecha para extender la vida de anaquel del fruto. AbstractPostharvest system of the soursop fruits (Annona muricata L.) is not yet fully developed, so there are several problems during fruit handling. Accelerated softening during postharvest storage, and its commercialization is a constant and very important problem. Soursop fruits are of climacteric type, characterized by its high respiration rate and ethylene production, coupled with a high enzymatic activity and its sensitivity to cold. Long storage periods are not yet possible, mainly due to the high susceptibility to cold damage. Scientific information on this subject is still limited and dispersed and although research has been carried out on this subject, it has been insufficient. This paper compiles the most important researches, especially about fruit generalities, respiration, ethylene production, maturation changes, enzymatic activity and postharvest storage techniques to extend the shelf life of the fruit.

Soursop fruit (Annona muricata L.) production is diminished by the attack of pathogens such as Nectria haematococca. However, the fruit–pathogen interaction at the biochemical and molecular levels is still unknown. The objective of this study was to analyze the response of the soursop fruit to the presence of N. haematococca during postharvest storage. Soursop fruits were inoculated with the pathogen and total phenolic compounds, antioxidant capacity by Ferric reducing/antioxidant power (FRAP), 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS•+), and 2,2′-diphenyl-1-picrylhydrazyl radical (DPPH•), as well as enzymatic activity and transcript levels of polyphenol oxidase (PPO) and superoxide dismutase (SOD), were evaluated at 1, 3, and 5 days of storage. The noninoculated fruits were the controls of the experiment. The highest total phenol content was recorded on day one in the inoculated fruits. FRAP, ABTS, and DPPH activity presented the highest values on day three in the control fruits. Inoculated fruits recorded the highest PPO activity on day five and a five-fold induction in the PPO transcript on day three. SOD activity showed a decrease during the days of storage and 10-fold induction of SOD transcript on day three in the inoculated fruits. Principal component analysis showed that total phenols were the variable that contributed the most to the observed variations. Furthermore, a positive correlation between total phenols and SOD activity, PPO expression, and SOD expression, as well as between DPPH and FRAP, was recorded. The results showed a differential response in antioxidant capacity, enzymatic activity, and gene expression during the interaction of soursop fruits–N. haematococca at postharvest storage.

The soursop fruit (Annona muricata L.) is a crop of significant economic value for Nayarit, which is characterized by having a bittersweet taste, making it attractive to the consumer. However, the soursop has rapid maturation which causes a short shelf life. Several postharvest management techniques have been applied to reduce its metabolic processes, such as refrigeration, use of 1-methylcyclopropene (1-MCP), and controlled and modified atmospheres. In recent years, polysaccharide-based coatings have been applied to fruits. Therefore, the objective of this investigation was to evaluate the physicochemical and biochemical changes, as well as the antioxidant activity of soursop fruits with a mucilage-based coating (2%), stored at 22°C and 15°C with a 90% RH. Weight loss, firmness, color, soluble solids, acidity, pH, phenols, flavonoids, vitamin C, and antioxidant activity were evaluated. The results obtained in the coated fruits stored at 15°C showed lower weight loss (6.4%), lower firmness (29.7 N), higher TSS concentration (10.4°Bx), and lower acidity (0.38%) compared with the uncoated fruits. The total phenolic content decreased in coated fruits stored at 22°C (54.3 mg EGA/100 g FW). The highest antioxidant activity (DPPH method) was recorded in fruits coated and stored at 15°C with an average value of 257.9 mg EAA/100 g FW. Moreover, a high concentration of vitamin C was observed in fruits coated and stored at 15°C and 22°C (20.5 and 17.5 mg EAA/100 g FW), concluding that the coating based on roselle mucilage (2%) in combination with a temperature of 15°C prevents weight loss, decreases titratable acidity, and increases the content of phenols and vitamin C. Furthermore, an increase in the shelf life up to eight days and in the antioxidant activity at the maturity of consumption was observed in the fruits coated with 2% roselle mucilage stored at 15°C.

Fruit and vegetable products are susceptible to the attack of fungi during postharvest handling. Chemical fungicides are the most commonly used technique to control fungal diseases. However, an alternative product is the use of plant extracts, which have been reported in in vitro and in vivo conditions. The objective of this investigation was to identify one of the main pathogens of mango and soursop fruits using morphological and molecular tools as well as to evaluate the in vitro inhibitory effect of papaya and soursop leaf and seed extracts. Two pathogens were isolated and identified by their morphological and molecular characteristics from mango and soursop fruits. We obtained extracts from leaves and seeds of soursop and papaya using five solvents of increasing polarity (hexane, acetone, ethanol, methanol, and water) through the ultrasound-assisted extraction technique at a frequency of 35 kHz and 160 W for 14 min. In vitro evaluations of the extracts were performed using the Kirby–Bauer technique. The extracts with the highest percentage of inhibition were analyzed qualitatively and quantitatively using standardized techniques of colorimetry and spectrophotometry. Furthermore, we determined the content of total phenols, flavonoids, alkaloids, terpenoids, anthraquinones, coumarins, and saponins. As a result, we identified the pathogens as Colletotrichum fructicola and Nectria haematococca. Aqueous extracts (water as a solvent) showed a higher percentage of inhibition of both pathogens compared with the other extracts. Furthermore, the aqueous extract of papaya leaf was the most effective among all extracts. The aqueous papaya leaf extract exhibited a percentage of inhibition of 49.86% for C. fructicola and 47.89% for N. haematococca. The aqueous extracts of papaya leaf and seed (AqEPL and AqEPS) presented the greatest amount of metabolites (except anthraquinones and coumarins). The aqueous soursop leaf extract (AqESL) presented the greatest amount of phenols, tannins, and flavonoids (219.14 ± 8.52 mg GAE/L, 159.84 ± 10 mg GAE/g dm and 0.13 ± 1.12 × 10−4, respectively). The aqueous soursop seed extract (AqESS) had the highest saponin content with 1.2 ± 0.1 mg QSES/g dm and the papaya leaf accusative extract (AqEPL) had the highest alkaloid content (6.413 ± 1 × 10−3 mg AE/g dm) compared with the other extracts. The AqESS had a lower content of secondary metabolites (sterols, alkaloids, and saponins), while AqESL showed no presence of alkaloids and coumarins.

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