Saleem, Shahzada Arshad (2005) ASPECTS OF RIPENING OF DHAKKI DATES (PHOENIX DACTYLIFERA L.) AND POST HARVEST STABILITY EMPLOYING HURDLE TECHNOLOGY. PhD thesis, Gomal University, D.I. Khan.
A research project was initiated at the Food Science and Technology Department, Faculty of Agriculture, Gomal University, Dera Ismail Khan, NWFP, Pakistan; to provide appropriate measures to reduce post harvest wastage through advance research, and to develop cheap and easily adaptable technology suiting our country's requirement. 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 methodology and appropriate storage and transportation facilities and lack of expertise. Since Dhakki date is a high quality fruit its demand for local consumption as well as for the export is ever increasing. However, its sale quality is uneven due to poor quality using conventional processing techniques. Further the fresh dates deteriorate rapidly on storage if not properly managed. The research study was undertaken with the aim to search out new avenues in order to cut down post harvest losses, boost up quality, increase yield and post-harvest stability, utilize surplus fruits to convert into the value added product, and to streamline flow of the production of Dhakki dates. In order to achieve objectives the following studies were carried out. The influence of water activity and storage atmosphere were studied. Absorption isotherm was constructed by relating equilibrium moisture content with water activity in the range of 0.12 to 0.97 aw. Further the dates were equilibrated at 0.52, 0.58 or 0.75 aw and packed into tin containers and flushed with nitrogen, oxygen or air prior to storage for 4 months. The stability of the date is evaluated by follow-up changes in moisture content, NEB, pH, titratable acidity and soluble solids content. The samples were also checked for slime appearance. The deterioration continued during the storage and the changes increase on increasing water activity of the samples, however were affected by the storage atmosphere. Samples kept at water activity of 0.58 aw retained characteristic date color and flavor, and the deteriorative changes were significantly reduced under the nitrogen atmosphere. In order to maintain desired quality characteristics for extended period it is desirable to store the dates at its own water activity of 0.62 aw under the nitrogen. Aspects of ripening and curing of Dhakki dates were examined by conducting experiments using hot water treatments, chemical means (sodium chloride & acetic acid), microwave radiation and freeze technology. Suitability of Dhakki dates was also evaluated for chhohara formation. The hot water treatment with 70.oC performed better than those with 35 oC and 93 oC, and resulted into a much better product with acceptable quality indices. The quality of the product is improved further appreciably and the yield boosted up from the level of 55 % to more than 70 % by optimizing treatment time to 3 min. Sodium chloride and acetic acid promoted ripening, however, sodium chloride appeared more effective producing 75 % greater yield than the control, and salt at 2 % was found as optimum for achieving quality product. Microwave radiation showed a great positive impact on the ripening qualities such as fruit length, width, and weight. A significant retention in fruit size appeared given radiation of medium intensity (480 W), and the fruits exposed for 50 sec attained almost original fresh fruit size and appeared attractive for being bigger and smooth in shape, and juicy as compared to the other treated fruits at lower intensities and to the control samples. Moreover, the Mw radiation boosted up the date forming process seven times, reducing the curing period sharply from 288 hr for the control samples to 40 hr for the samples that were Mw radiated for 50 s at 480W. In conjunction with microwave radiation the stage of maturity of the dates also offered a positive response to the ripening process thereby enhancing yield of the product substantially and maturity levels at the late Doka stage with hardness level of 180-200 mmHg.cm-2 believed the attractive maturity range for the ripening. Moreover, the radiation at 480W facilitated early harvesting of dates prior to attaining to optimum maturity stage thereby saving at least two weeks hanging of the dates on the tree, and hence the damage by monsoon rain is expected to be reduced whilst the desirable qualities of the dates held intact. The impact of reduced temperature for storage of Doka was evaluated. The Doka harvested at mature and astringent stage was stored at 10, 0 and -15oC for a year and the quality in terms of hardness index, appearance of mold growth, acceptability and rate of the curing! drying, yield, quality, and storage stability of the product was examined. The chilled Doka was also given pot. alkali treatment prior to curing! drying at 40 oC The Doka converts into the ripened Dong soon after thawing, and sustains freezing effectively, yet causes stiff skin patchy product on curing/drying The feature is skillfully mended by giving potash alkali treatment resulting into a product with much improved quality, enhanced yield and stability to storage at 40 oC The process envisages high potential in streamlining flow of a superb quality product. Although Dhakki variety is well known for yielding quality dates having great demand within and outside the country, however, to get more return and save surplus produce from various detrimental factors the suitability of Dhakki dates has been explored for chhohara formation. The chhohara prepared out of the fruits with maturity of 350-300 mmHg.cm-2 hardness and given 25 minutes boil was found to possess bigger size and bulky weight, and confers superior organoleptic qualities, and shows high potential for commercial exploitation.
|Item Type:||Thesis (PhD)|
|Uncontrolled Keywords:||dhakki dates (phoenix dactylifera l.), hurdle technology, date crop, post harvest losses, date palm, freeze technology|
|Subjects:||Arts & Humanities (b)|
|Deposited By:||Mr. Muhammad Asif|
|Deposited On:||25 Nov 2006|
|Last Modified:||22 Jan 2009 20:43|
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