Study of Different Agents that Improve Firmness of Guava Fruits during Ripening

Guava (Psidium guajava L.) is a climacteric fruit that is mainly consumed fresh. However, it is a highly perishable fruit, which ripens quickly (5 to 7 days at room temperature) with accelerated firmness loss and quality changes. In addition, the over production in the last months of the year causes drop of price and market saturation. For this reason it is important to look for postharvest alternatives in order to maintain the fruit firmness which could help to increase its commercialization in faraway markets. Applications of calcium as well as the use of inhibitors of ethylene action (1-MCP) in postharvest have managed to maintain firmness and fruit quality, due their ability to strengthen the bonds between the polysaccharides of the cell wall maintains the stability of the membrane against the hydrolytic enzyme action, reduces the water absorption and delays the senescence. Nevertheless there has been no success in maintaining fruit quality for its exportation. Therefore the objective of this work was to evaluate different firmness agents based on calcium during storage of guava fruits cv. 'Media China'. Guavas were treated in pre-harvest with KelatexCa+B® and Ca‑Metalosate® and in post-harvest were treated with CaCl₂ (0,1,2 and 3%) at vacuum and atmospheric pressure, Ca-Metalosate®, Mg-Metalosate® and their combination (0.08 M, respectively) and XP-Amino (0,1,2 and 3%) and stored at 10 ºC for 8 days. Fruits were analyzed at day 0 and 8. Weight loss (WL), total soluble solids (TSS), titratable acidity (AT), firmness (F), and visual quality (VQ) were measured. TSS and AT showed no significant differences between treatments. In pre-harvest fruit treated with Ca-Metalosate® presented the best firmness (46N±15), whereas in post-harvest fruit treated with 3% CaCl₂ (40N±12) was the best_, while fruit treated with KelatexCa+B and 3% XP-Amino had the lowest firmness ((24±6) and (26±12), respectively). The results showed that fruit treated in pre-harvest presented the best firmness, showing no significant difference with control (39N±13), although the visual quality and subjective firmness were better. Suggesting that, the application of pre-harvest calcium could maintain firmness and quality of guava fruits. Therefore it is necessary to conduct further studies maintaining our target on applications of calcium on pre-harvest.