| Abstract: |
In 2009 and 2010 seasons, Washington navel (WO) and Valencia orange (VO) fruits were prepared for exportation on Jan. 1st and March 15th, respectively in Belbeis Packing House, Sharkia Governorate. The following 10 stages were adopted: 1- exclusion of decayed and injured fruits ; 2- primary grading to exclude very small fruits ; 3- washing by water (pH 11.8- 12.1) + 0.5% sodium orthophenyl phenate at 30-32˚C; 4- rinsing by water shower followed by disinfection by Guazatin (1.25 / l) + Brifos-k (0.625 / l )/ 250 l of water; 5- primary draying by hot air (48-50˚C); 6-manual discard of fruits with insect or mechanical injuries. ;7-waxing by a mixture of water-wax + TBZ(1.5/l) + Imazalil (0.4/ l) / 200l ; 8- final draying at 48˚C; 9- final grading (grades I & II); 10- packing in carton boxes comprised 80 and 100 fruits of WO and VO cvs., respectively.The fruits were then immediately brought to Postharvest Laboratory, Dept. of Hort. Fac. of Agric., Zagazig Univ. Fruits of each cv. received stickers showing sequential numbers and the fresh weight of each fruit. The fruits were then re-packed in smaller carton boxes, each contained 30 fruits. Each variety was represented by 12 boxes, i.e. 360 fruits. Further 15 fruits (5 fruits × 3 replicates) were used to determine fruit physical and chemical characteristics before the onset of cold storage. The 12 boxes of each cultivar were stored at 3±1˚C and 90± 5% RH for 12 weeks. During this period six samples, each comprised 60 fruits, were taken out of cold storage (CS) room at biweekly intervals to disclose the changes in physical and chemical properties of the fruits. At each date (2, 4, 6,8,10 &12 weeks of CS), 15 fruits of each sample were taken directly after getting out of storage room to study the effect of CS period. The other 45 fruits were held under 20˚C to simulate the conditions of marketing period [the shelf life period (Sh L P)]. The Sh L P continued for 15 days during which 3 samples [one sample at each 5 days, i.e. 5, 10, 15 days] were taken to study the physical and chemical changes in the fruits; each sample comprised 15 fruits (5 fruits×3 replicates).In conclusion, the fruits revealed the following behavior:1. With the advance of shelf life period, significant increments were observed in fresh weight losses and TSS/acid ratio of both cvs. in the two seasons. Meanwhile, significant reductions were observed in peal firmness, pulp firmness, juice percentage, panel test index, TSS%, total acidity % and vit.C. content. Other tested parameters (fruit decay and chilling injury) indicated insignificant response to shelf life period.2. The longer cold storage periods (10 & 12 weeks) resulted in higher fresh weight losses and TSS/acid ratio. On the other hand, the longer cold storage period prior to shelf life caused significant reduction in panel test index, total acidity and vit.C. content as well as pulp firmness and juice percentage. The fruit decay %, chilling injury % and peel firmness as well as, juice percentage and TSS of Washington navel orange did not affected by cold storage period.3. The 18 combinations of each cv. in both seasons reflected nearly the same features as the main factors.
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