Enhancement of Post Harvest Quality and Stability of Dhakki Dates using Advanced Technology

Abstract

Date palm (Phoenix dactylifera L.) has been cultivated since time immemorial and the dates are the largest dried fruit produce in the world. Now in Pakistan, the date fruit has become one of our important cash crops, and Pakistan is the 5th leading country for dates production and export. However the date crop in general and the Dhakki date in particular, are facing certain problems like fall of monsoon season coincided with date ripening season, want of preservation methods like appropriate date storage and transportation facilities and lack of expertises. Since dhakki date is a high quality fruit its demand for local consumption as well as for the exports is ever increasing. However, its sale quality is uneven due to lack of advance processing techniques, and further the fresh dates deteriorate rapidly on storage if not properly managed. The study was undertaken with the aim to improve commercial quality of Dhakki date to increase its production. Initially the survey was conducted to estimate the amount of produce, find causes of quality deterioration and to assess the extent of damage to produce. The attention was focused to examine determinants affecting ripening/curing of Dhakki dates, optimization of the post harvest process(es), evaluating the stability of the processed dates taking advantage from the advances made in this field exploiting the potentials of Drive/Hurdle technology, and UV and Microwave radiations. The survey revealed that many wild groves and germplasms of Date palm varieties were available in D.I.Khan. However, some prominent and commercial varieties are Shakki, Zaidi-I, Khudrawi, Basra, Shakri, Azadi, Gulistan, Shamran, Hillawi, and Zaidi-II. All commercial varieties are generally cultivated in the Chasma Right Bank Canal irrigated areas. There are very few commercial Date palm growers in D.I Khan, however the number is increasing. Several localities including village Dhakki were selected for conducting trials and collecting samples. Samples were brought in the laboratory of the Department of Food Science & Technology, Faculty of Agriculture for investigation. Extra efforts over two years period of a short duration were focused to examine the root causes and nature of quality degradation after the harvest and during storage of the dates. The following appropriate measures are suggested in order to up-grade the local technology:- 1. High quality date fruits shall be selected for processing as the quality over and above the fresh commodity can’t be improved ay any after processing technology. 2. Fruits of an optimum maturity stage at late “Doka” or “Dong” are required. This is one of the most important factors responsible to achieve better yield of quality product. The fruits are cleaned and well washed before further processing. 3. Ripening is enhanced and superior quality produce can be accomplished by chilling the fruits over night before curing and drying. 4. Balancing of fruits for 5 min at 70 C in clean water preferably containing NaCL (0.1%) and NaOH (1.0%) or acetic acid, accelerates ripening. Instead of bleaching, an application of physical injury to fruits also favours ripening. 5. Sun drying may be performed under cleaned and hygenic conditions using solar driers. OR the fruits can be dried by keeping on clean mats completely enclosed in a hood of transparent plastic sheet with proper ventilation. 6. By the isothermic studies, it is predicted that the processed Dhakki dates be dried to a level until to attain water activity in the range of 0.62 to 0.65 A, at which microbial, biochemical and chemical deteriorative changes are minimum. The produce can maintain its high quality over a long period of one year by keeping the processed fruits at a room temperature with 0.62 to 0.65 Aw, and packaged sealed in cellophane sheets or using materials which help maintaining water activity constant. 7. An acceptable quality of chhohara from the unfertile and otherwise waste fruits can be obtained by boiling the fruits in water for 35 min until change in the colour occurs. The taste is much improved if 1-2% sugar or 5% waste date pulp is added to the boiling water. 8. Microwaves are potentially capable for ripening/curing of fruits and maintaining original fruit size without causing deformation in appearance of the product provided the intensity of radiation is precisely caliberated. By proper use of microwave radiation of medium intensity (480 watts) for about a minute, picking of fruits even before reaching the optimum maturity level becomes possible, while keeping the desirable qualities of the dates intact. Hence the problem caused by monsoon rain might be resolved by the use of microwave radiation. Microwave treatment also improves yield. Solar drying further furnishes shine. It is envisaged that the post havest quality as well as storage stability of Dhakki dates be much improved advance technology based on the present experimentation and findings are adopted by the date growers, processors and allied personnels.