changes in physical and biochemical traits in native summer-ripening apple cultivars during cold storage

research was carried out in 2007 on 7 native summer-ripening apple cultivars grown in kamal abad karaj research station. the 16 year-old plants were grafted onto seed rootstocks. the cultivars were ghandak-e-kashan, golab-e-isfahan, golab-e-kohanz, mashad, assali, ghermez-e-rezaieh and a new cultivar--koli-e-mahallat (syn. escr). the aim of the study was to identify changes in qualitative and quantitative traits occurring during cold storage of summer-ripening apples to determine their genetic potential. the fruits were harvested in two stages. the period of cold storage was predetermined to minimize cold storage time for early cultivars and was set at 4, 8, and 16 weeks based on ripening class. the testing intervals were weekly, bi-weekly and 4-weekly testing, respectively. the temperature and relative humidity of the cold storage room were fixed at 0° ± 0.5° c and 80% ± 10%, respectively. physical and biochemical traits under investigation included weight, firmness, total soluble solids (tss), titrable acids (ta), ph and flavor index (defined as the ratio of tss/ta). the results showed that cultivar and harvest time had significant differences. the least loss of fruit weight was observed in koli-e-mahallat at the end of cold storage of the first harvest samples. however, for the second harvest, it was recorded in all the cultivars except golab-e-isfahan. the greatest firmness registered in golab-e-isfahan at the end of cold storage and in ghandak-e-kashan and ghermez-e-rezaieh for the second harvest. at the end of cold storage, the highest tss (>12%) was recorded for golab-e-kohanz; highest ph (<4) and ta values (>40%) for mashad. assali and golab-e-kohanz had the highest flavor index (tss/ta>60%) at the end of cold storage for the first harvest. koli-e-mahallat, assali, golab-e-isfahan and golab-e-kohanz had the highest values for the second harvest.