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Abstract This study was conducted during two successful seasons of 2013 and 2014 to improve fruit quality of Early sweet grapes (Vitis vinifera L.,) as affected by Arabic gum, potassium silicate and modified atmosphere packing (MAP). Early sweet grapes were harvest from a private vineyard in Cairo Alexandria desert read, Giza Governorate, Egypt. The grapevines cultivar Early sweet were five years old, grown in sandy soil under drip irrigation system and planted at 1.5 X 3.0 meter. Cultural practices were done according to general field recommendation including fertilization, pruning as well as pest diseases control. Clusters were picked in early morning at the ripening stage in middle of June during both seasons. Ripening stage (TSS ≈ 14 – 15 %) and acidity (0.4 – 0.5 %), complete yellow color of berries skin and clusters hand harvest. Healthy clusters free from physiological and pathological were chosen. Moreover, uniformity clusters size, color and firmness were observed. Clusters were harvested in carton bags, and then immediately transported from the orchard to the postharvest laboratory at the Department of Horticulture, Ain Shames University and treated on the same day. Clusters were washed with tap water containing color x 1% (0.05% sodium hypochlorite) and air dried, then divided into groups and treated with following treatments. The used treatments were 1. Clusters treated with 1.5 % potassium silicate (PS) were wrapped using heat shrinkable films (SH) (PS + SH). 2. Clusters treated with 1.5 % potassium silicate (PS) were packaged in modified atmosphere packaging (MAP) by using 40 mu (PS + MAP 40 mu). 3. Clusters treated with 1.5 % potassium silicate (PS) were packaged in modified atmosphere packaging (MAP) by using 80 mu (PS + MAP 80 mu). 4. Clusters treated with Gum Arabic (GA) (25% w/v) were wrapped using heat shrinkable film (SH) (GA + SH). 5. Clusters treated with Gum Arabic (GA) (25% w/v) were packaged in modified atmosphere packaging (MAP) by using 40 mu (GA + MAP 40 mu) 6. Clusters treated with Gum Arabic (GA) (25% w/v) were packaged in modified atmosphere packaging (MAP) by using 80 mu (GA + MAP 80 mu) 7. Control clusters: untreated clusters.Treated clusters were rapidly and carefully were placed in three perforated carton boxes (30×40×20 cm) for each treatment. Each box contained 2 kg clusters was replicated three times and the experiment was repeated twice (2013 and 2014 seasons). Boxes of all treatments were subjected randomly to one of the pervious treatments and stored at 1. Refrigerator at O ± 1 Co with 90 ± 5% RH for 28 days. 2. Refrigerator at 7 ± 1 Co with 90 ± 5% RH for 28 days 1. Effect of different treatments on physical properties of Early sweet grape under cold storage 1.1 Weight loss percentage It is clear that weight loss increased gradually during the storage period of Early sweet grape stored at 0 and 7oC. The highest weight loss for clusters dipped in potassium silicate (PS) or in Gum Arabic (GA) plus wrapped by perforated polyethylene (PPE) bags 80 mu with no significant between them. On the other hand the least values of weight loss were for the clusters dipped in potassium silicate or dipped in Gum Arabic plus wrapped by shrink film (SH). At the end of storage period the control gave the highest significant percentage of weight loss. 1.2 Berry Decay Percentage Decay percentage was increased considerably with prolonged storage period in all treatments in both storage degrees for two seasons. All treatments significantly reduced the decay of Early sweet grape than the control treatment during both season and both storage temperature. The lowest values for decay percentage were obtained as a result of dipping clusters in Gum Arabic (GA) or potassium silicate (PS) plus warped by heat shrink (SH). 1.3 Berry Shatter Percentage Berry shatter percentage was gradually increased by storage period advanced for two storage degrees in both seasons. Thus, clusters dipped in Gum Arabic or potassium silicate and warped by heat shrink significantly reduced berry shatter % than the control with no significant deference between them at the end of storage period. Potassium silicate with heat shrink treatment (PS + SH) had the lowest significant percentage of shatter percentage at both degree storage during both seasons at the end storage period. Dipped in potassium silicate or Gum Arabic and wrapped by PPE 80 mu, untreated clusters gave the highest percentages of shattering with no significant differences among them. 1.4 Discarded Berries Percentage Discarded berries percentage was gradually increased by storage period advanced. Dipping Early sweet grape in potassium silicate (PS) and wrapped with shrink film (SH) significantly reduced the percentage of discarded berries percentage in two seasons at both degree storage than the other treatments or the control. Meanwhile, clusters were dipped in Gum Arabic plus covered by shrink film (GA + SH) was given near value to potassium silicate (PS). 1.5 Bunch Freshness The color changing of bunches were acceptable and the browning of stem, rachis increased during storage. However, it was maximum in case of control fruits compared to all another treatments. Dipping in Gum Arabic or potassium silicate and warped with heat shrink and control was highly significant. This indicating that antifungal action of gum Arabic and potassium silicate and another material tested in warp. 1.6 Berry Firmness The average firmness decreased as the storage period increased reaching its lowest values at the end of storage in both storage degrees during two seasons. The highest significant value of berry firmness obtained from dipping in potassium silicate or Gum Arabic with covering by polyolefin heat shrink flowed by dipped in potassium silicate with covered by polyethylene bags 40 mu in descending order as compared with the control treatment and Gum Arabic with polyethylene bags 80 mu in both seasons which gave the lowest significant values. 1.7 Berry adherence strength The higher berry adherence found in grapes dipping in Gum Arabic plus wrapped by shrink film (GA + SH) so also potassium silicate with shrink film (PS + SH). Berry adherence strength was gradually reduced by storage period advanced till 28 days. Potassium silicate with shrink film (PS+SH) reduced berry adherence strength from harvest day to end storage in both degrees for two seasons. The highest level suggested for control nearly using Gum Arabic with perforated polyethylene 80 mu (GA + PPE 80 mu) with no significant value. 2. Effect of different treatments on chemical properties of Early sweet grape on cold storage 2.1 Total Soluble Solids PERCINTAGE (T.S.S%) Total soluble solids content of stored fruits gradually increased with extend of storage period during both seasons under study. On the end of storage days, the untreated clusters and treated clusters with potassium silicate and gum Arabic plus profited polyethylene 40 and 80 mu give the lowest values of T.S.S without significant different between them. On the contrary potassium silicate with heat shrink (PS + SH) to reach the highest value to Gum Arabic with heat shrink (GA + SH) as compared with the control treatment. 2.2 Total Acidity Percentage After 7 days storage no significant differences were noticed between different treatments and both storage temperature. The significant differences appeared after 14 days, Gum Arabic treatment plus heat shrink achieved the least percentage of acidity during both season under study respectively. 2.3 Total Soluble Solids / Acid ratio: Maximum value for dipped on gum Arabic with heat shrink (GA + SH) while the lowest value were suggested to dipped on Gum Arabic and covered with profited polyethylene 80 mu (GA + PPE 80 mu) at 0Co in first season while storage under 7Co maturity index were in the same trend with change in values for each treatment. 2.4 Respiration Rate Noticeable decrease in values of rates of respiration at end of cold storage period compared with the initial respiration rate values at harvest day in all postharvest treatments during the two seasons of investigation. Dipping in Gum Arabic (GA)or potassium silicate (PS) and wrapped by shrink film (SH) tend to have the effective role in reducing the rate of respiration of grape clusters. 3. Effect of different treatments on Early sweet grape at market temperature for 7 days after cold storage 3.1 Effect of different treatments of physical properties on Early sweet grape at market temperature for 7 days after cold storage The best treatment for dipped in potassium silicate (PS) or Gum Arabic (GA) and wrapped by shrink film (SH) (PS + SH) or (GA+ SH) tend to have a good quality and appearance with no significant difference between them, they have a significant decreased weight loss, decay, shatter and total loss berries percentages compared with all treatments so also berry firmness and berry adherence which suggested highest significant value compared with all treatments. On the other hand untreated treatment (control) and dipped in Gum Arabic and covered by profited polyethylene 80 mu (GA + PPE 80 mu) were the worst results with no significant different between them as compared with all treatments. This is true for the two seasons of the study 3.2 Effect of different treatments of chemical properties on Early sweet grapes at market temperature for 7 days after cold storage Total soluble solids (T.S.S), acidity percentages, T.S.S / acid ratio and respiration rate were affected with long storage and marketing duration. T.S.S% and T.S.S / acid ratio values were converging to increase after week of marketing while acidity values were decreased for dipping in potassium silicate (PS) or Gum Arabic (GA) and wrapped by shrink film (SH) (PS + SH) or (GA + SH). While worst treatment for dipped in Gum Arabic and covering by profited polyethylene 80 mu it was nearly with value of control treatment with no significant between them so it assisted on TSS, acidity and TSS / acid ratio. When subjected respiration rate (gm CO2/Kg/h) we find that no differences between all treatments. This is true for the two seasons of the study. |