Studies on the Ripening Aspects and Fruit Quality of Date Palm (Phoenix dactylifera L.) Cvs. "Hillawi and Khadrawi

Date palm is an important fruit crop in the world as well as in Pakistan. It provides a rich and quick energy source to humans and also plays a significant role in the social and economic life of the people living in dry areas. Monsoon rains at the time of fruit harvesting or ripening are very harmful and heavy fruit losses occur resulting rotting, fruit drop and uneven fruit ripening. Unfortunately, in Pakistan serious losses occur due to these rains at the time of fruit harvesting/ripening. The research work reported in this manuscript was conducted in the Experimental Fruit Orchard Square Number 9 and Post Graduate Agricultural Research Station (PARS) (Latitude 31o-26´ N, Longitude 73o-06´ E and Altitude 184.4 m), Institute of Horticultural Sciences, University of Agriculture Faisalabad, Punjab Province, Pakistan. In the field studies, effectiveness of ethephon application (foliar and injection) and strands thinning practices on ripening acceleration and fruit quality of date palm were investigated and found that ethephon application with spray showed superiority over injection method to accelerate the maturity and ripening processes of date fruits in both Hillawi and Khadrawi cultivars. Fruit sprayed with ethephon (4 ml/L and 2 ml/L) at final kimri and early khalal stages reached at rutab stage 13 and 6 days earlier and showed uniform fruit ripening indexes of 60.46 and 44.85% and rutab fruit yield (6.29 and 4.37 kg ) per bunch with good fruit quality composition than the untreated fruits. Second field experiment was conducted to explore the role of strands thinning on maturity enhancement and fruit quality. Strands thinning practices were carried out with following intensities (no thinning, 20% RCS (removal of central strands), 30% RCS, 20% STT (shortening of terminal tips), 30% STT, 20% RCS + 20% STT and 30% RCS + 30% STT) at early kimri stage (4 weeks after pollination). It was observed that strands thinning practices improved quality characteristics than the fruit those were untreated (without thinning) in both cultivars. Strands thinning intensity @ 30% RCS alone resulted in 10 days earlier maturity and higher rutab yield of 5.22 kg per bunch and more uniformly ripe fruit (76.28%) at rutab stage. The total soluble solids, ascorbic acid, sugars (glucose, fructose and sucrose), total phenolic, total flavonoids and total antioxidants were significantly improved while titratable acidity and total tannin contents were decreased in thinned fruits. In post-harvest experiments, hot water exposures for 3 and 5 min at 65oC in Hillawi and Khadrawi cultivars reduce the fruit ripening period up to 6 days and produced uniformly ripened fruit (73.33 and 81.66%) with better quality and higher acceptability of organoleptic scores marked by the panellists as compared to \ud untreated fruit. Acetic acid @ 3% showed higher uniform ripening index of 64.24% with higher total soluble solids, sugars, total phenolic, total flavonoids, total antioxidants and organoleptic properties after incubation at 40±1oC for 72 h. In the last study different sun drying techniques were used for the curing of soft Hillawi dates. Among different sundrying techniques, SDT4 (DSE with removal in baskets and covered during night) proved good regarding the fruit quality composition such as TSS, acidity, total sugar, reducing sugar, total phenolics, total antioxidants, total flavonoids with lower amounts of total tannin contents. In conclusion, a spray application of ethephon @ 4 ml/L at final kimri stage, strands thinning @ 30% RCS alone at early kimri stage, hot water treatments at khalal stage (3 min for Hillawi and 5 min for Khadrawi) and acetic acid @ 3% at khalal stage showed better results to accelerate the fruit ripening period and produced higher index of uniformly ripe fruits with good fruit quality composition in both date palm cultivars. Among different sun-drying techniques in fruits harvested at rutab stage, SDT4 (DSE with removal in baskets and covered during night) proved good regarding the fruit quality composition in Hillawi date palm cultivar. Uniformity in ripening gave extra benefits and higher economic returns were achieved by adopting these technologies and it provided higher economic return