Physiological and Physicochemical Behavior of Soursop Fruits Refrigerated with 1-Methylcyclopropene

Transcriptome Analysis of Soursop (Annona muricata L.) Fruit under Postharvest Storage Identifies Genes Families Involved in Ripening

Soursop (Annona muricata L.) is climacteric fruit with a short ripening period and postharvest shelf life, leading to a rapid softening. In this study, transcriptome analysis of soursop fruits was performed to identify key gene families involved in ripening under postharvest storage conditions (Day 0, Day 3 stored at 28 ± 2 °C, Day 6 at 28 ± 2 °C, Day 3 at 15 ± 2 °C, Day 6 at 15 ± 2 °C, Day 9 at 15 ± 2 °C). The transcriptome analysis showed 224,074 transcripts assembled clustering into 95, 832 unigenes, of which 21, 494 had ORF. RNA-seq analysis showed the highest number of differentially expressed genes on Day 9 at 15 ± 2 °C with 9291 genes (4772 up-regulated and 4519 down-regulated), recording the highest logarithmic fold change in pectin-related genes. Enrichment analysis presented significantly represented GO terms and KEGG pathways associated with molecular function, metabolic process, catalytic activity, biological process terms, as well as biosynthesis of secondary metabolites, plant hormone signal, starch, and sucrose metabolism, plant–pathogen interaction, plant–hormone signal transduction, and MAPK-signaling pathways, among others. Network analysis revealed that pectinesterase genes directly regulate the loss of firmness in fruits stored at 15 ± 2 °C.

Edible Coating Based on Roselle (Hibiscus sabdariffa L.) Mucilage Applied to Soursop Fruits in 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.

Cold Storage of Two Selections of Soursop (Annona muricataL.) in Nayarit, Mexico

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.

Effect of the application of 1-methylcyclopropene and wax emulsions on proximate analysis and some antioxidants of soursop (Annona muricata L.)

The effect of the application of 1-methylcyclopropene (1-MCP) and wax emulsions, alone or combined, on composition analysis, vitamin C, polyphenols, and antioxidant capacity of soursop was evaluated. Fruits were stored as follows: at 25°C (control), and at 16°C: fruits sprayed with candelilla or flava emulsions, fruits treated with 1500 nL/L of 1-MCP (20°C, 12 h), and fruits treated with 1-MCP and then sprayed with emulsions. Fruits were allowed to ripen and the edible part was used for analysis. Only fruits stored at 16°C without 1-MCP showed visible symptoms of chilling injury. Fruits treated with 1-MCP combined with flava emulsion maintained in greater extent their vitamin C content, dietary fiber, total phenolics content, and antioxidant activity. The combination of 1-MCP and emulsions can be utilized in postharvest handling of soursop because this combination can preserve its nutritional composition and antioxidant activity.