Influence of orchard factors on apple harvest quality and postharvest performance

Abstract

Focusing on both preharvest and postharvest elements, this study investigates how crop load affects apple growth, development, and quality. A worldwide important fruit crop, apples have been grown for over two thousand years, with more than 10,000 types known. Several elements affect apple quality, including environmental factors, genetic factors, and orchard management techniques. The impacts of crop load were investigated on both physiological and metabolomic features, hence stressing its significance as a main factor of ultimate apple fruit quality. The study underlines how apple quality is affected by preharvest variables and how suitable postharvest handling can maintain this quality over storage, hence encouraging more apple consumption. Current regulation and consumer demand provide high economic value for fruits with superior sensory and nutritional qualities. Improvement of apple fruit quality is impossible postharvest. Hence, optimum apple quality at harvest and during postharvest and subsequent, consumer satisfaction, is achievable through understanding the influence of preharvest factors. A large-scale study on the effect of crop load on 'Gala' fruit growth and development and on harvest internal quality and maturity was performed. Hand thinning was used to achieve three crop load treatments: heavy load (978 fruit/tree), commercial load (598 fruit/tree), and light load (380 fruit/tree) that were compared to unthinned trees (1614 fruit/tree). Parameters studied were yield, fruit size during growth and development and at harvest, fruit red overcolor blush, starch index, flesh firmness (FF), soluble solids concentration (SSC), dry matter content (DMC), index of absorbance difference (IAD), return bloom and fruit set (next season). Non-destructive models that utilize visual to near infrared spectroscopy (Vis-NIRS) were used to predict internal quality in terms of DMC, SSC and IAD. Apple thinning decreased fruit yield, increased fruit size, DMC, and SSC, improved fruit red overcolor blush and advanced fruit maturity based on IAD. However, it did not affect the starch index and FF. Vis-NIRS technology accurately estimated DMC and SSC at 729-935nm, and maturity based IAD. Additionally, IAD did not correlate with FF but described better fruit physiological maturity. Non-destructive technologies that predict internal fruit quality and maturity are powerful tools that provide a better understanding of the effect of pre-harvest factors on apple fruit quality. In terms of postharvest performance, fruits coming from distinct crop load management treatments were treated or not with 1-methylcyclopropene (1-MCP, 1000 μl 1-1, 24 h, 0o C) an ethylene action inhibitor and known for its effect on prolonging apple fruit quality. Following pre-storage treatment or not with 1-MCP apples coming from heavy, commercial, light crop loads and unthinned trees were cold stored (0oC, 95%, RH) for up to 3 or 7 months. After cold storage fruits were transferred at room temperature (20oC, 90% RH) to simulate retail market conditions and apple ripening was characterized immediately at 0, 4 and 8 days. Collectively, crop load and 1-MCP significantly affected apple fruit storage performance. Fruit coming from lighter crop loads had increased levels of SSC during postharvest ripening due to higher DMC and expressed significantly lower softening rates during storage potentially because of increased carbohydrates pool (DMC and SSC) that potentially correlate with delayed deterioration. Treatment with the 1-MCP through inhibition in respiration and ethylene production blocked fruit ripening, retained higher DMC and SSC levels, and delayed softening and loss of titratable acidity (TA) during postharvest compared to untreated fruits. These results are of high importance for the apple industry as they demonstrate that proper preharvest management could lead to robust postharvest performance.