Abstract

Sweet cherry becomes a very important crop for Chilean fruit industry being the most planted specie during the last 10 years. Introduction of self fertile cultivars, improvement of storage life though generalized use of modified atmosphere packaging and the lack of competition from other Southern Hemisphere´s countries are the main facts that explain this situation. Although sweet cherry deteriorates rapidly during storage, fruit darkening, stem water loss and decay are reduced significantly with cooling and fruit packaging under modified atmosphere bags. These technologies have allowed Chilean sweet cherry to achieve long distance market by vessel at more reduced cost than airfreight and access high demanding market as Asian countries. Nevertheless fruit pitting and bruising are considered the main causes of sweet cherry rejection and repacking in markets. High risk of decay characterizes this damaged tissue that reduces fruit quality prize and long term business. Impact and compression damage are the main causes of pitting and bruising symptoms. The damage occurs at harvest, fruit transportation and during fruit packaging; but symptoms are not visible until 10 days of storage at 0°C. Consequently the damaged fruits appear in the market because there not be sorting in the packing line and can not be reduced by the modified atmosphere packaging. Fruit sensitivity to mechanical damage is very cultivar depending. Bing is considered one of the most tolerant, in comparison with the most planted cultivar Sweetheart considered very sensitive. Not only there is high variation on fruit sensitivity among cultivars but also from different orchards and seasons in the same cultivar. Commercial effort to reduce pitting and bruising has been focused on improvement of cultural practices for better fruit handling, identification of main points of damage, reduction on dropping height and removing rough surface in the packing line. However little effort has been concentrated to understand the parameters associated to fruit sensitivity to mechanical damage and how they can be modified with the agricultural practices or how to segregate the fruit sensitivity to this damage at harvest. The main hypothesis behind this research is that Rheological properties of the fruit tissue (elasticity, plasticity, force to bioyield) and/or biological (maturity, turgor, pectin) and/or mineral fruit concentration should explain fruit susceptibility to pitting and bruising among varieties and variation produced in the same variety. Preharvest practices can be evaluated in term of these rheological, biological and mineral parameters to focus on improvement of mechanical resistance and fruit segregation at harvest. The general objective of this research is to determine the rheological and biological parameters associated with the sensitivity of the sweet cherry to mechanical damage. The specific goals associated are: 1. Determine biological characteristic produced during preharvest management of sweet cherry that affects fruit sensitivity to mechanical damage. 2. Evaluate the most relevant rheological properties of fruit tissue associated with sensitivity to mechanical damage. 3. Characterize the parameters of fruit maturation associated with fruit sensitivity to mechanical damage. 4. Determine the values of biological parameters to allow segregation of fruit tissue to mechanical damage sensitivity. Therefore at the end of this research growers can focus in the agronomic practices associated to improve cherry tolerance to pitting and bruising and exporter will be able to segregate fruit sensitivity in relation to rheological and biological parameters evaluated at harvest.