الفهرس 
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Abstract
The aim of the present work was the keeping quality of orange and sweet pepper fruits throw coating them with different emulsions containing polysaccharide (chitosan and pectin) combined with some aromatic compound (lemongrass oil ,thyme oil and funnel oil) and lactic acid bacteria. The results of this study showed the following.
1- The GC-MS results showed that, the major compound in Lemon grass oil was Gerarial (48.73%) followed by Neral (37.58%), the major compound in Thyme oil was Thymol (28.57%) followed by ϒ-Terpinene (16.49 %) and the major compound in Fennel oil was Methyl chavicol (82.12%) followed by Limonene (9.48%).
2- The surface tension of pure distilled water at 200 C was estimated to be 72 mN/m but the surface tensions value of tap water at 250 C recorded 68.3 mN/m. Dissolving pectin or chitosan in water reduced the surfaces tension of the suspension to the level of 54.5 and 55.5 mN/m respectivly. On other side, emulsions of pectin or chitosan with lemon grass oil recorded further lowering of surface tension value to the level 51.7 to 52 mN/m respectivly.
3- The chitosan and pectin with the emulsion of three spice essential oils showed considerable inhibitory potential against pathogenic bacteria. It was observed that chitosan has high antagonistic effect in comparing to pectin against tested culture (E.coli ,Staphylococcus aureus and Salmonella typhimurium). Lemongrass oil gave antagonistic effect on tested bacteria ranged from 0.8 to 2.033 cm with pectin and from 0.667 to 2.267 cm with chitosan. Whereas the thyme in coating agent recorded the antagonistic effect ranged from 0.67 to 2.84 cm with pectin and from 0.4 to 3.2 cm with chitosan. The lowest antagonistic effect was recorded by fennel oil with pectin or chitosan as coating emulsions. The results show that the most efficient coating treatments were CHL and PL at 5%, which gave a broad effect on tested culture. The lemongrass oil was more effective than thyme and funnel oil on microbiological growth. Emulsion of lemon grass oil or fennel incorporated in pectin appeared the highest values of inhibition zone at 5% and 2.5% against Pencillium spp. giving (1.8, 1.967)cm and (1.367, 1.467)cm in respective order. However, in presence of chitosan, the growth of Pencillium spp. were recorded at 5% of emulsion of lemon grass (1.967cm) and fennel (1.633 cm) oil. Individual chitosan or pectin treatment gave the lowest effect against all tested cultures comparing to the other treatments. The results show that the most efficient coating treatments were CHL and PL, which gave a broad effect on tested cultures.
4- Study the effect of coating formulation on the preservation of orange fruits showed that, the bacterial count on orange was 3.9log CFU/g at zero time and this count was gradually decreased during storage period with all coating treatments. The control treatment, (orange sample without any coating) recorded the highest count (9.4 log CFU/g) after 90 days of storage period followed by pectin treatment, Wherease the orange sample treated by pectin with emulsion of lemongrass oil or chitosan with or without emulsion of lemongrass oil recorded the lowest viable count. Immediately, before the application of the formulation, the count of yeast and mold was 1.7 log CFU/g. The mold and yeast count increased gradually during storage period reached to 7.44 log CFU/g with control sample (without coating) but in the case of CH and CHL at 5%, the count of yeast and mold was ranged between 6.24 to 6.52 log CFU/g during 90 days. It was observed that Salmonella typhimurium was not detect with CH and CHL (5%). The lowest values of Salmonella typhimurium was achieved by PL treatment giving 1.3 log CFU/g. The most effect treatment was CHL followed by PL comparing to control treatment. At the end of storage, the survival of Staphylococcus aureus showed a significant decrease when applied with coating- forming agents
5- The untreated control orange fruits recorded 25.6%weight loss at the end of storage period (90 days). However, they were totally infected and covered with mold cells after 18 and 36 days of storage. Coating the fruits with pectin or chitosan as well as their emulsion with lemongrass oil drastically reduced the weight loss to only 3 and 4.98% at the end of cold storage period.
6- Decay rate could be expressed as percentage of the infected fruits during storage. Control treated fruits show higher decay rate reaching 15% after 90 days of storage. On other side, coating the fruits with pectin or chitosan and their emulsion with lemongrass oil reduced the decay rate to the level of 3% to 6%. The results show that chitosan emulsion was an efficient treatment in reducing the fungal infection and rotting of the orange fruits.
7- Firmness is a major characteristic for the quality of orange fruits during storage period. Untreated control samples were rapidly decayed and their peels were softened during storage. The firmness value was decreased by 40% after 18 days of storage and this decrease in firmness was continued until reaching only 10.95 N at the end of storage period (90 days). All coating treatments reduced the firmness deterioration, since the loss in firmness was only 8.5% after 18 days of storage. The final loss in firmness of pectin or chitosan coated samples was 31% while the loss in control sample reached 82% at the end of cold storage. Final firmness losses in orange samples coated with pectin and chitosan emulsions was 35.3 and 19.8%, respectively.
8- PH value of the fresh fruits was 3.76. During storage, control and uncoated fruits recorded the highest pH-value (4.48 and4.49) after 90 days of storage period. On other side, orange fruits coated with pectin, pectin emulsion, chitosan and chitosan emulsion recorded the lowest change in pH-values, since the recorded values were in the range of 4.2 to 4.29 at the end of storage period (90 days).
9- The respiration rate at zero time recorded 19.7 to 19.78 mgCO2 /kg.h. Coating slightly reduced the respiration intensity of the tested fruits. The respiration rate of control fruits was still high (15.52 mg CO2 /kg. h) even after 90 days of storage period. On the other side, all coated fruits samples recorded lower respiration rate, which also further decreased with the progress of storage period. Orange fruits coated with the chitosan or chitosan emulsion recorded the lowest respiration rate (10.3 to 10.44 mgCO2 /kg. h) at the end of storage.
10- The surface color of the orange fruits is important parameters. The lightness (L- value) of the fresh orange sample was 63.2 and this value was slightly increased during the first month of storage period and reached an average value 61.5 for the treated samples, while untreated control sample showed (L-value) of 58.9, being lower than, the treated orange sample. The redness (a-value) recorded a score of 19.48 for tested orange fruits at zero time. Control untreated orange fruits, as well as those coated by pectin solutions showed a gradualy increase in (a- values) during the 90 days storage periods. On the other side, these samples coated with chitosan or chitosan and pectin emulsions showed almost stable (a- values) during the cold storage periods. All fresh orange fruits showed a well developed yellow color, since the (b-value) recorded 66.6. The uncoated control orange sample maintained this color shade until the end of storage period. On the other side, Navel orange sample coated with chitosan emulsion showed some loss in yellowness towards the end of cold storage period (after 54 days). chroma (c-value) showed similar behavior to those of a and b color scores. The Hue-value of fresh orange fruits was 73.7˚which is close to the full yellowness Hue of 90˚. In principle, the control and treated sample maintained this Hue value until the end of storage period (90 days).
11- The color index (CI) of orange fruits at zero time recorded a value of 4.63. During storage, the color index of untreated control sample was increased until 54 days and then decreased. All treated fruits showed also, in principle, an increase in the CI-scores until 72 days of storage, especially those coated with pectin solutions or chitosan emulsion, at the end of storage period (90 days).
12- The Total Solible Solid (TSS) value of the fresh orange fruits was 14.20 brix. During cold storage, the TSS value of the control (uncoated fruits) was increased to 18.10˚ Brix at the end of the storage period (90 days). TSS values were also increased in the coated fruits but with lower intensity than that of control sample. Coated sample, especially these coated with chitosan or chitosan emulsion showed the lowest change in TSS value during storage period.
13- The Titratable Acidty (TA) content of control untreated orange fruits was reduced by more than 50% at the end of storage period, while coated fruit sample showed lower losses during the storage period, especially these coated with chitosan emulsion, which showed the lowest level of only 10.5% at the end of storage period.
14- The TSS/ acid ratio of the control fruits was 51.7, while those coated with pectin, chitosan or their emulsions recorded lower TSS/acid ratio in the range of 21.6 to 27.6. Coating reduced the moisture losses, keeping acidity from sharing respiration process. The high sweetness degree of the control orange samples could be referred to the high loss in weight (moisture content), the higher concentration ratio of the remaining soluble solids and the intensive use of acids in respiration process.
15- Ascorbic acid content in the fresh orange fruit was 35.8 mg/100g pulp. Control uncoated orange fruits loosed about 80% of their vitamin C content after 90 days of cold storage. Coating the fruits with pectin or chitosan emulsion reduced the losses to about 34%, especially those fruits coated with chitosan emulsion.
16- The pigment concentrations in the pulp of fresh orange fruits were 0.087, 0.189 and 0.69 mg/L, respectively for chlorophyll a, chlorophyll b and total carotenoids. The level of chlorophyll a and b decreased, with some fluctuation, during the cold storage period accompanied with gradual increase in content of total carotenoids. In principle, chlorophyll a and b disappeared completely at the end of cold storage (90 days). The concentration of carotenoid was increased by 1.56 to 2.83 folds at the end of cold storage. On other side, the concentration of carotenoid was increased by 1.56 to 2.83 mg/L folds at the end of storage period. The accumulation and biosynthesis of carotenoids has been observed during fruit storage and cold storage turn this change slowly than those stored under atmospheric condition.
17- Chitosan with emulsion recorded the highest degrees of sensory attributs ( texture, color and aroma) in all storage periods compared to treatment (C) which recorded the lowest degree of texture, aroma and color in all storage periods.
18- The effect of coating formulation on the preservation of sweet pepper fruits was studied. The promising treatments of pectin ,chitosan , pectin with emulsion of lemon grass oil, pectin with Lactobacillus acidophilus ,chitosan with emulsion of lemon grass oil and Lactobacillus acidophilus only, were applied to protect and control postharvest decay pathogens during storage. The results indicated that the pectin and chitosan with or without emulsion of oils decreased the total bacterial counts during storage period (28 days) comparing to control treatment at 10˚C.The results show that total bacteria was higher in control than in all other treatments. During 14 days of storage period, total bacterial count was reduced as affected by coating with the chitosan, pectin, emulsion of lemon grass oil and lactic acid bacteria single or in combined treatment compared with the control treatment (untreated). The corresponding data were 4.78, 4.76, 4.76, 4.72, 4.67 and 4.73 log CFU/g with pectin, pectin + emulsion of lemon grass oil, chitosan, chitosan + emulsion of lemon grass oil, pectin with Lactobacillus acidophilus and Lactobacillus acidophilus only compared to control. During storage period, the count of mold and yeast ranged from 4.26 to 7.35 log CFU/g with control treatment, wherease it was ranged from 3.86 to 5.8 log CFU/g and 3.84 to 5.86 log CFU/g with pectin and pectin + emulsion of lemon grass, respectively. In respect to chitosan and LAB treatment, the mold and yeast count were ranged from 3.74 to 5.44& 3.69 to 5.2 & 3.72 to 5.25 and 3.72 to 5.36 log CFU/g for chitosan, chitosan + lemon grass oil , Lactobacillus acidophilus + pectin and Lactobacillus acidophilus only respectively. At the end of storage period the count of Staphylococcus aureus, E. coli and Salmonella typhimurium were 5.3, 2.01 and 1.93 log CFU/g in control treatment, wherease the pectin , pectin + emulsion of lemon grass , chitosan and chitosan + emulsion of lemon grass treatments recorded 1.96, 1.88, 1.8 , 1.7 log CFU/g for Staphylococcus aureus 1.85, 1.69, 1.58 , 1.6 log CFU/g for E. coli and 1.81, 1.77, 1.61 , 1.55 log CFU/g for Salmonella typhimurium in respective order. The LAB treatment gave recorded 1.69, 1.62, 1.6 log CFU/g with Lactobacillus acidophilus treatment and 1.8, 1.69, 1.78 log CFU/g with pectin + Lactobacillus acidophilus treatment for Staphylococcus,E.coli and Salmonella, respectively.
19- Throughout storage, the weight loss of uncoated sweet pepper fruit was significantly greater than that of coated fruit. After 28 days of storage, uncoated peppers showed 17.4% weight loss, whereas the losses of samples coated with chitosan/emulsion and pectin/emulsion were 5.6% and 5.9% respectively.
20- The results showed the incidence of decay were 10, 7 and 4% for C, P, PL samples, respectively, after 7 days of storage. Decay rate was greater in the uncoated sample compared to the coated fruits. The percentage of decay was 30% for control treated fruits, and all treated samples were ranged from 8.1 to 25.2%, and the best treatments were CHL which reduced the decay to 8.1% after 28 days from storage at 10°C.
21- The firmness value of pepper was 50.7 N (control treatment), and it was gradually dropped over time. For the control uncoated pepper sample, the firmness reached 34.51 N representing about 31.2% loss of original firmness at the end of storage period. In addition, samples treated with lactic acid culture only (CLa) showed about 20.5% loss in firmness. Wheares all other coated samples showed losses in firmness in the range of 12.5% to 2.9% after 28 days.
22- The respiration rate of control pepper fruit was still high (20.46 mg CO2/kg.h) even after 28 days of storage. On other side, all coated fruits samples recorded lower respiration rate, which also decreased with the progress of storage period. Pepper fruits coated with the chitosan or chitosan emulsion recorded the lowest respiration rate (13.42 and 11.78 mg CO2 /kg. h) at the end of cold storage.
23- The redness values were increased towards the red- orange color shade during storage. For control sample, a-value was 42.68 after 28 days of cold storage. For coated samples, a value, ranged from 33.59 to 39.47 at the end of cold storage period. The lowest change in the a- value was recorded for pepper sample coated with chitosan emulsion. The yellowness b- value of the pepper sample was 25.5 at zero time and this value was decreased to the range 8.53 - 20.05 at the end of cold storage period. The highest loss in b –value was recorded in the control sample (8.53). While the lowest value was recorded in coated sample by chitosan and chitosan emulsion being 19.21, 20.05 respectively. The lightness of the control pepper sample .L- value was 35.1 at zero time. However tested pepper sample showed lower lightness value ranging between 13.68 to 27.15 at the end of storage period. The highest loss in L-value was recorded for the control sample (13.68) during the cold storage, while the lowest loss was recorded for chitosan emulsion (27.15). chroma values of the fresh fruits was 33.75 and it was increased to the level of 39.11 to 43.52 at the end of cold storage. The Hue- value is an important color parameter because it indicate the type of govering color. Fresh pepper samples showed Hue value of 49.08 , which is an indicator for red- orange color type. Control sample showed the highest darkness in color with the Hue of only 11.3˚ at the end of cold storage period, while pepper fruits sample coated with chitosan emulsion kept the red – orange color type with a Hue value 30.83˚ at the end of cold storage.
24- Results revealed that the fruits treated with CHL retained the highest amount total solible solids (TSS) (7.8ºB) followed by PLa (7.6ºB), CH (7.1ºB), PL (6.9ºB), P (6.8ºB) and CLa (6.2ºB), respectively. On the other hand, minimum TSS content (4.9ºB) was recorded in control fruits, which were significantly lower than other treatments.
25- The ascorbic acid content had shown a decreasing trend in all the samples during storage at 10 ˚C. Higher reduction was noted in the ascorbic acid content of control samples (uncoated) during storage from 115.85 to 40.73 mg/100gm. The coated pepper retained ascorbic acid content compared to the control, where ascorbic acid values were recorded for the treatments being 85.3, 97.58, 104.55 ,108.6, 106.86, and 84.24 for P, PL, CH,CHL, PLa, and CLa, respectively at the end of storage period.
26- There was no significant difference in total carotenoids contents during the cold storage. The differences were significant between control samples compared with treated sample. Peppers treated with CHL had the highest carotenoids content (9.1 mg/100g), followed by CH, PLa, PL, CLa and C giving 8.68, 8.61, 7.98, 7.36, 7.15 and 6.9 mg/100g, respectively.
27- The untreated pepper fruits samples recorded the highest decrease in flavonoid content in all storage periods (from 76.95 to 41.9 mg catechin Eq./100 g). The decomposition of flavonoids can be attributed to the action of the enzyme peroxidase and the treated samples P, CLa, PL, CH, PLa and CHL recorded the lowest reduction in flavonoid content (63.35, 64.9, 70.9, 71.2, 71.9 and 72.3mg catechin Eq./100 g), respectively at the end of storage period.
28- A decrease in antioxidant activity was observed in all peppers samples with aging during storage. The control samples showed the high decrease in the antioxidant activity after 28 days of storage where it decreased from 59.9 %to 19.5 %.
29- Due to the early ripening of pepper fruit, the control samples showed an initial phenolic content of the fresh pepper fruits was 151.12 mg/100g during storage, phenolic cotent rose in all pepper samples. The conversion of flavonoids to secondary phenolic compounds is responsible for the rise in phenolics.
30- Sensory evalution showed that flavor degrees for the C and CLa treatments recorded the lowest flavor scores after 28 days.At the end of cold storage period, it was observed that there was a decrease in the flavor degrees for the control treated samples comparing to 7th day except CH and CHL treatments, which were not affected.