الفهرس 
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Abstract
Nowadays, there is an increasing demand to the consumption br of natural cloudy fruit juice either fresh or chilled and not -#102;-#114;-#111;-#109; br concentrate (NFC). Also, the consumers prefer the natural juice additives br which give not only good sensory attributes but also contain effective br antioxidant compounds. The main quality criteria in cloudy fruit juices br are the cloud stability which provides freshness, flavour and aroma. br Clouding agents (Cas) are usually added to fruit juices or fruit beverages br to increase turbidity and provide a natural pleasant appearance. Synthetic br Cas are very stable, but consumers prefers those natural products. In br addition, the legislation is becoming more and more restrictive on the br utilization of synthetic products as food additives. Several studies were br carried out to utilize some fruit juice processing wastes and by-products br as clouding stabilizers. These by-products -#102;-#114;-#111;-#109; fruit juice processing br represent a major problem as wastes and nowadays clean technology in br food industry is preferred. They may be promising sources of compounds br which can be used due to their favorable stabilizing or antioxidant br properties. br Therefore, the main objective of this investigation was to br evaluate a natural Cas -#102;-#114;-#111;-#109; apple pomace and orange peel prepared by br either fermentation or manufacturing of phenol concentrate. The br evaluation parameters were cloud stability, degree pectin methyl esterase br inhibition, viscosity, antiradical activities and phenolic degradation, nonenzymatic br browning, sensory evaluation as well as volatile constituents. br Part I- Effect of flavour stabilizers on cloudy apple juice (CAJ) br quality br 1-Cloud stability br 1-1-The effect of traditional flavour stabilizers (Xanthan, CMC, β- br cyclodextrin, pectin and arabic gum) as well as apple pomace phenol br concentrate (APPC) and fermented apple pomace (FAP) on cloud br stability of apple juice was measured by spectrophotometer at 660 nm. br The effect of added compounds on cloud stability increased with br increased concentration. br 1-2-CMC is more effective for stabilizing cloudiness when added to a br natural cloudy apple juice compared to xanthan. The addition of br clouding agents significantly increase the cloud stability of CAJ as br compared to the control sample (P ≤ 0.05), the best results were in the br treatment of fermented apple pomace at 4 and 25 0 C. br 1-3-The cloud stability of all samples showed a significant reduction br (P≤0.05). While arabic gum was the least effective cloud stabilizer br (57.3%) at level of 0.5 g/100 ml juice at the end of storage for two br weeks at 4 0 C, -#119;-#104;-#101;-#114;-#101;as the fermented apple pomace was the most br effective one (86.4%) at the same level. br 2-Pectin methyl esterase (PME) inhibition br 2-1-PME inhibition during storage at refrigerator was more effective than br that at room temperature. Xanthan was the best inhibitor among the br traditional flavour stabilizers -#119;-#104;-#101;-#114;-#101; it gives an inhibitory effect at br level 0.05 g/100 ml juice 80.4% and 72.9% after storage at 4 and 25 br 0C, respectively. br 2-2-Enzyme inhibition values by fermented apple pomace and apple br pomace phenol concentrate were 81.4% and 80.4%, respectively, at br the end of storage at 4 0C for two weeks. On the other hand, the br inhibition values at 25 0C were 71.9% and 72.9%, respectively. br 3-Rheological properties br 3-1-The apparent viscosity was measured at shear rates -#102;-#114;-#111;-#109; 1.0 to 437.4 br S-1 for CAJ samples treated with different clouding agents and br compared to untreated sample as control. The juice viscosity values br gradually reduced with increasing shear rate till reached their minimal br values at shear rate 437.4 S-1. br 3-2- The flow behaviour index (n) of all fresh, stored and treated samples br were less than 1.0 giving a value ranged -#102;-#114;-#111;-#109; 0.0486 to 0.097; a br pattern indicating their strong non-Newtonion pseudoplastic br behaviour. Also, noticeable reduction in consistency (K) was found br to occur in both control and treated samples during storage of 4 days br at 25 0C. br 3-3-The apparent viscosity of CAJ treated with apple pomace phenol br concentrate as well as fermented apple pomace products proved the br minimum values in comparison to other treatments. While, the br addition of clouding agents increased the viscosity of treated CAJ br significantly (P≤0.05) as compared to the control sample, maximum br increase of viscosity was observed in that treatment of xanthan. br 4-Antioxidant activity and phenoilc degradation br 4-1-Antioxidant activity of CAJ samples treated with traditional and br prepared flavour stabilizers were carried out by DPPH0 and br compared with commercial apple juice samples. br 4-2-The maximum antioxidant activity in sample treated with apple br pomace phenol concentrate during storage at refrigerator and at br room temperature were 68.7% and 78.8%, respectively. br 4-3- The minimum EC50 was obtained in those treatments of apple br pomace phenol concentrate and fermented apple pomace which br were 197.9, 456.3 μL, respectively, after two weeks storage at 4 0C br and 213.3, 223.5 μL, respectively, after four days storage at the br room temperature. br 4-4-The traditional flavour stabilizers showed EC50 as following arabic br gum (1059.5 ul), Β-cyclodextrin (1315.2 μL), pectin (1628.4 μL), br CMC (2746 μL), xanthan (2743 μl) at the end of storage at br refrigerator. While, the commercial apple juice samples showed the br least EC50 values at both storage temperatures, 2759, 1943 μL at 4 br 0C and 3219, 2853 μL at 25 0C. br 4-5-Radical scavenging activity measured by using Electron Spin br Resonance (ESR) of sample treated with apple pomace phenol br concentrate demonstrated significantly (P≤0.05) the strongest br activity of radical scavenging (95.7%) followed by fermented apple br pomace (90.8%), B-cyclodextrin (88.4%), pectin (87.4%), xanthan br (70.2%) and arabic gum (62.8%) -#119;-#104;-#101;-#114;-#101;as CMC showed the least br scavenging activity (50.6%). br 4-6-As the time and temperature of storage increased significantly br (P≤0.05) increase in phenolic degradation had occurred. Good br correlation was found between phenolic degradation and antioxidant br activity. br 4-7-A total of 10 phenolic compounds were identified in cloudy apple br juice, the obtained results showed that chlorogenic acid was the br predominant phenolic compound. br 4-8-It was observed that apple pomace phenol concentrate had total br phenol concentration as determined by HPLC as it was 300.2 br (mg/L) and found to be higher than fermented apple pomace which br was 234.4 (mg/L). br 5-Non-enzymatic browning (NEB) br 5-1-Absorbance at 420 nm has been exploited to determine NEB of br cloudy apple juice treated with different flavour stabilizers. br 5-2- Data showed that apple juice samples treated with apple pomace br phenol concentrate and fermented apple pomace show less br browning indices when compared to other treatments at the three br levels studied. br 5-3- Glucose, fructose and sucrose are the main three sugars found in br apple juice samples. A remarkable increase in browning indices br with prolonged storage time and temperature has occurred, coupled br with a reversible relationship with added compounds concentrations. br 5-4-Samples treated with apple phenol concentrate and fermented apple br pomace proved that have had the highest level of sugar, being, 25.2 br and 23.73 (g/L), respectively. br 5-5-Hydroxymethylfurfural (HMF) content was determined at the end of br storage at 4 0C using HPLC and the least values were elucidated in br the treatments of apple pomace phenol concentrate (0.09 μg/L), br followed by fermented apple pomace (0.16 μg/L), -#119;-#104;-#101;-#114;-#101; the highest br value was found in the treatment of arabic gum (12.4 μg/L) and the br other treatments were descendingly arranged as following; xanthan br (0.86 μg/L), B-cyclodextrin (0.67 μg/L), pectin (0.31 μg/L) and br CMC (0.28 μg/L). br 6-Sensory evaluation and volatile constituents br 6-1-Sensory evaluation was done to compare between fresh and treated br cloudy apple juices -#119;-#104;-#101;-#114;-#101; there were remarkable differences between br both and in between the treated ones -#119;-#104;-#101;-#114;-#101; the odour, taste, br appearance and overall acceptability were concerned. br 6-2-The results have indicated that the highest overall acceptability score br were obtained in samples treated with apple pomace phenol br concentrate and fermented apple pomace. br 6-3-Twenty-three volatile compounds were detected by the GC-MS and br FID, the relative concentrations of volatile compounds were br calculated by comparing the peak area of the compound to their br similar on the standard curve of ethyl butanoate. br 6-4-The detectable volatile compounds classified into five groups, 17 br esters, 2 aldehydes, 2 alcohols, 1 monoterpene hydrocarbons and 1 br ketone. The esters and alcohols are accounting for 70.5 % and 12.4 % br of total volatiles, respectively. While, ethyl butanoate is considered to br be the major component of the ester fraction being 2.83 for fresh br sample but after storage for two weeks it was drastically reduced to br 0.27 μg/L . br 6-5-Juice samples treated with apple pomace phenol concentrate and br fermented apple pomace gave the highest esters content when br compared to other treated samples. On the other hand, ethyl butanoate br and ethyl-2-methyl butanoate had the highest aroma values up to 942 br and 306666, respectively, in this sample treated with apple pomace br phenol concentrate. br Part II- Effect of flavour stabilizers on orange juice quality br 1-Cloud stability br 1-1-The addition of hydrocolloids and orange peel phenol concentrate br (OPPC) as well as fermented orange peel (FOP) showed similar br trend mentioned in apple treatments. br 1-2-Treatment with fermented orange peel and orange peel phenol br concentrate showed no significant (P≤ 0.05) difference compared br with xanthan especially at concentration (0.05 g/100 mL juice) and br storage at 4 0C and at concentration (0.03 g/100 mL juice) and br storage at 25 0C. br 2-Pectin methyl esterase (PME) inhibition br 2-1-The data showed that the inhibition values of PME reached to 79.8% br and 72.4% when orange juice was treated with fermented orange br peel and orange peel phenol concentrate, respectively, after storage br for two weeks at 4 0C. br 2-2-The inhibition values were as high as 80.6% and 72.2% under the br same aforementioned treatments after 4 days storage at 25 0C. br 3-Rheological properties br 3-1-The flow behaviour index (n) of all control and treated orange juice br samples were less than 1.0, a pattern which indicated their strong br non-Newtonian pseudoplastic. (K) Values obtained were 100.28 and br 83.51 Pa.S of control samples stored 14 days at 4 0C and 4 days at br 25 0C, respectively. br 3-2- The sample treated with orange peel concentrate indicated slightly br higher (K) value than sample treated with fermented orange peel br being 135.14 Pa.S for the former and 128.94 Pa.S for the latter after br 4 days of storage at 4 0C. However, both samples had 127.33 and br 116.88 Pa.S, respectively, after 4 days storage at 25 0C. The values br of consistency coefficient (k) ranged -#102;-#114;-#111;-#109; 123.86 for pectin at zero br time on the first level (0.1g/100 ml juice) up to 152.9 Pa.S for br recorded xanthan at the same conditions. The increase in the br consistency coefficient was the highest with the addition of xanthan br and CMC. br 3-3-The results showed that the sample without hydrocolloid has the br lowest viscosity 2.53 cP and that the samples with orange peel br phenol concentrate or fermented orange peel exhibited slight br increase in viscosity, being, 3.65 and 3.51 cP, respectively, br compared to arabic gum and Β-cyclodextrin samples which had br values of 3.79 and 3.76 cP, respectively. br 4-Antioxidant activity and phenoilc degradation br 4-1-The percentage of antioxidant activity was significantly increased as a br function of increasing concentration of clouding agents. A br reversible relation between antioxidant activity of clouding agents br and storage period and temperatures. Among all treatments studied, br orange peel phenol concentrate had the highest antioxidant activity br using DPPH0 (70.8%), followed by fermented orange peel (69.3%), br when storage was carried out at refrigeration. br 4-2-The minimum EC50 was obtained in that treatments of orange peel br phenol concentrate after two weeks storage at 4 0C and four days br storage at 25 0C, respectively. br 4-3-The highest radical scavenging activities using ESR were br descendingly arranged as orange juice treated with orange peel br phenol concentrate and fermented orange peel (97.4 and 93.8%, br respectively) then B-cyclodextrin (73.5%), pectin (71.9%) and br CMC (69.7%) as well as xanthan (68.4%), -#119;-#104;-#101;-#114;-#101;as arabic gum br showed the least efficiency (62.5%). br 4-4-The phenolic degradation showed a significant decrease during the 14 br days under the applied experimental conditions. After 4 days of br storage at 4 and 25 0C the phenolic degradation in control samples br decreased by 32.3 % and 39.4 %, respectively. At the end of br storage, both treatments of orange peel phenol concentrate and br fermented orange peel of juices showed a significant decrease br (P≤0.05) in phenolic degradation. br 4-5-A total of 13 phenolic compounds were identified and quantified in br treated orange juice, the obtained results showed that both hesperdin br and cinnamic acid were the major phenolic compounds in orange br juice. br 4-6- Samples treated with orange peel phenol concentrate and fermented br orange peel contained higher contents of ascorbic acid, were 43.4 br and 41.2 mg/L after two weeks of storage. Commercial orange juice br samples had least concentration of phenoilcs determined by HPLC br -#119;-#104;-#101;-#114;-#101; the maximum concentration was 28.26 mg/L, the least br treatment of flavour stabilizers under investigation had 88.08 mg/L br in the treatment of CMC. br 5-Non-enzymatic browning br 5-1-The browning indices were significantly increased as a function of br increasing storage time and temperature. The three major sugars br namely fructose, glucose and sucrose are usually found in a ratio of br 1:1:2. br 5-2- According to the obtained data the lowest value of HMF obtained in br the treatment of orange peel phenol concentrate followed by br fermented orange peel was (0.054 and 0.64 μg/L, respectively) br while the highest value was obtained in the treatment of arabic gum br treatment 13.83 (μg/L), xanthan (2.39 μg/L), Β-cyclodextrin (1.83 br μg/L), pectin (1.72 μg/L) and CMC (1.53 μg/L). br 6-Sensory evaluation and volatile constituents br 6-1-The sensory evaluation of the treated orange juice samples revealed br that a significant increase (P≤0.05) in sensory attributes of the br sample treated with orange peel phenol concentrate (OPPC) and br fermented orange peel (FOP) compared to the control and the br hydrocolloids under investigation especially those concerned with br the taste. br 6-2-Twenty-five volatile compounds have been identified after separation br on DB-5 column as important in the flavour of orange juice. These br compounds are recorded together with their linear Kovat indices br (LKI) and Odour threshold values (OTVs) in orange juice. br 6-3-The maximum aroma values were found in esters of fresh sample of br ethyl butanoate, hexyl acetate and ethyl hexanoate which were 304, br 164 and 16 respectively. br 6-4-Samples treated with orange peel phenol concentrate and fermented br orange peel appeared highest value of esters and aldehydes br especially (nonanal). br Part III- Effect of microwave heating on cloudy apple and orange br juices quality br 1-Chemical composition of cloudy apple and orange juices br 1-1-Apple and orange juices had pH of 2.63 and 3.97, respectively, br titratable acidity value in apple juice was 0.85 and in orange was br 0.93%. Non-enzymatic browning was higher in apple juice (0.226) br than orange juice (0.213), an opposite trend was observed for total br soluble solids were 10.3 and 11.5% in apple and orange juice, br respectively. While the orange juice yield was 48.0 mL/100g br -#119;-#104;-#101;-#114;-#101;as apple gives 65 ml/100g. br 2-Cloud stability br 2-1-The treatment at 90 0C had more cloud stability than at 70 0C -#119;-#104;-#101;-#114;-#101; br no significant difference was found between both temperatures at br zero time. After 2 months of storage at 25 0C there is significant br difference (P ≤ 0.05) between two temperatures. br 2-2-Relative turbidity (T%) values for cloudy apple juice heated at 90 0C br were found to be 80.3% and 70.2% after two months storage at 4 br and 25 0C, respectively, -#119;-#104;-#101;-#114;-#101; orange juice exhibited 75.6% and br 68.8% under the same conditions. br 3-Polyphenoloxidase (PPO) and pectin methyl esterase (PME) br inhibition br 3-1-The results indicated that by heating juices at temperatures 70 and 90 br 0C it was possible to inactivate the PPO (approximately complete br inhibition) and the PME enzymes. -#119;-#104;-#101;-#114;-#101;, the inhibition values of br PPO in orange juice at the end of storage at 4 0C were 93.8%, br 96.8%, after microwave heating at 70 and 90 0C, respectively. br 3-2- Concerning PME inhibition values in orange juice were 82.7%, br 90.2% which heated at 70 and 90 0C and storage for two months at 4 br 0C. br 4-Microbiological analysis br 4-1-Effects of microwave heating at 70 and 90 0C on the total aerobic br plate counts and the yeast and mold counts of cloudy apple and br orange juices stored at 4 0C for 60 days were carried out using nutrient br agar and potato dextrose media, respectively. br 4-2-The total plate counts after microwave heating treatment for cloudy br juice samples at 70 and 90 0C were 2.3X102 , 1.6X102 (cfu/ml), br respectively, and in orange juice samples at the same storage br temperature were 3.7 X102 , 3.3 X102 (cfu/ml), respectively after two br months at 4 0C. br 4-3-The mold and yeast in apple juice at 70 and 90 0C were 3X102, 2.3 br X102 (cfu/ml) respectively. Orange juice samples contain 6.6X102 , br 6.3X102 under the same conditions. br 5-Phenoilc degradation and antioxidant activity br 5-1-During the storage time at 4 0C no significant changes were observed br in phenolic degradation during microwave heating. On the other br hand, there is significant (P≤0.05) decrease in phenolic degradation br in juice samples stored at 25 0C. br 5-2-The antioxidant activities decreased with increasing microwave br heating temperatures. For instance, after being heating cloudy apple br juice at 70 and 90 0C, the DPPH0 scavenging activity of apple juice br was decreased -#102;-#114;-#111;-#109; 76.5% at zero time to 64.3% at the end of br storage at 4 0C and -#102;-#114;-#111;-#109; 66.8% to 58.3%, respectively. The br decreasing values in orange juice heated at 70 and 90 0C were -#102;-#114;-#111;-#109; br 89.6%, 78.5% at zero time into 71.6%, 60.2%, respectively, after br two months of storage at 4 0C. br 6-Volatile constituents br 6-1-Volatile compounds were identified and quantified in the headspace br of cloudy apple and orange juices. The concentrations of volatile br compounds in headspace gas were shown as peak area to standard br curve of ethyl butanoate. br 6-2-Twenty-six and twenty-five volatile constituents were identified in br cloudy apple and orange juice, respectively. While, the volatile br constituents in cloudy apple juice included 4 alcohols, 18 esters, 2 br aldehydes and 2 hydrocarbons. The majority of the identified br compounds (twenty-five) in orange juice were reported previously br as constituents of orange juice included 7 aldehydes, 8 esters, 3 br alcohols, 3 ketones and 4 hydrocarbons compounds as major class br of constituents. br 6-3-The concentrations of esters such as butyl acetate, hexyl acetate, butyl br hexanoate, and hexyl hexanoate in headspace of cloudy apple juice br were unaffected widely by microwave heating. br 6-4- It was found that methanol and ethanol were the most common br alcohols in both fresh and treated orange samples. Hydrocarbon br terpenes namely limonene, myrcene, α-pinene, and p-cymene are br the four terpene hydrocarbons found in processed orange juices br under investigation. br In conclusion: In the present investigation, we elucidate several br hydrocolloids which are used in fruit juices as clouding agents to provide br both desirable appearance and mouth feel properties, however no br previous study revealed the exploitation of natural antioxidant extracted br -#102;-#114;-#111;-#109; (apple pomace and orange peel) and used also as natural flavour br stabilizers to extend the shelf-life of fresh juice, therefore, as far as the br authors are aware the present study is the first trial to obtain such target. br Also, -#102;-#114;-#111;-#109; the technological point of view it is recommended to use such br by-products with the increasing demand for natural food additives and br clean technology.