Studies on Physico-chemical Changes During Fruit Growth, Maturity and Storage of Kiwifruit (Actinidia deliciosa Chev.) Grown in Kashmir Valley.

The present investigation was carried out in the Division of Pomology, Sher-e-Kashmir University of Agricultural Sciences & Technology of Kashmir during 2006 & 2007. To study the physico-chemical changes during growth and development of two kiwifruit cultivars Allison and Hayward, the fruits were collected at 15 days interval from 30 to 195 days after full bloom (DAFB) and the first sampling commenced one month after 80% full bloom. On the basis of fruit size and weight a double sigmoid growth curve was observed in cv. Hayward and Allison. The L/D ratio was found to be highest during Stage II at 90 and 105 DAFB for Allison and Hayward respectively. With respect to firmness, both cultivars had higher firmness during initial sampling dates which declined gradually but significantly with advancement of sampling period while as titrable acidity was quite low during early stages of fruit growth and increased significantly to its peak value at 135 DAFB and 150 DAFB for cv. Allison and Hayward, respectively after which a gradual decline was observed. Total soluble solids (TSS) increased significantly at slower rate till 105 DAFB in Allison and 90 DAFB in Hayward fruits, thereafter the rate of increase in TSS suddenly picked up in both the cultivars. However a gradual increase was recorded in total sugar, reducing sugar and non reducing sugar from 30 to 195 DAFB in both cultivars. Sugar/acid ratio was quite high initially but gradually declined up to 105 DAFB in Allison and 90 DAFB in Hayward followed by an increasing trend thereafter, while as the ascorbic acid content increased at a steady rate till 150 DAFB in Hayward and Allison and decreased gradually afterwards. With respect to the mineral nutrients the nitrogen content increased significantly with the initial period of growth and declined to rise again as the fruit entered into stage III while as the phosphorous and potassium contents of the developing kiwifruit increased significantly in the early stage of fruit growth till 75 DAFB and then registered a gradual decline later. However a slight increase in phosphorous was again recorded at 120 DAFB. The fruit calcium and magnesium content were significantly higher during the initial period of growth and declined and tended to level off towards the end of sampling period. To determine optimum picking maturity date and to study the storage behaviour of fruits in relation to harvest time after 10, 20, 30 and 40 days of ambient storage, two kiwifruit cultivars were harvested at weekly intervals commencing approximately one week before to three weeks after the anticipated harvest date (i.e. 4th November). The study revealed that fruit size, fruit weight, L/D ratio, organoleptic ratings, titrable acidity, non-reducing sugar, sugar/acid ratio and ascorbic acid showed non-significant variation at different harvesting dates and cannot be taken as reliable indices of maturity. However, fruit firmness, total soluble solids, total sugar and reducing sugar can be taken as reliable indices of maturity in kiwifruit as they varied significantly at different harvest dates. The optimum maturity date in Allison and Hayward was attained around 28th October and 4th November which correspond to 176 and 174 DAFB in Allison and 180 and 177 DAFB in Hayward during 2006 & 2007, respectively. After 40 days of storage, fruits harvested around 28th October and 4th November maintained the best quality and exhibited the lowest physiological loss in weight (5.83 and 5.61%), titrable acidity (0.97 and 1.04%), best eating firmness (1.42 and 1.47kg/cm2) and retained the higher values of organoleptic rating (3.95 and 3.95 points), total soluble solids (15.17 and 16.67%), total sugar (10.71 and 11.51%), reducing sugar (9.52 and 10.21%) and non-reducing sugar (1.17 and 1.23%) at 30 days of storage in Allison and at 40 days of storage period in cultivar Hayward, respectively while earlier or later pickings resulted in marked reduction of these quality parameters