الفهرس | Only 14 pages are availabe for public view |
Abstract This study was carried out on 12 agro-industrial waste samples. They were as follows : potato peel, eggplant peel, prickly pear peel, pomegranate peel, banana peel, mango peel, orange peel, peanut skin, pea pod, faba bean (broad bean) hull, chickpea hull and guava leaves. The main objectives of this study were: 1. to determine the total phenolic compounds, identify and the quantity of the main phenolic compounds. 2. to study their activities as antioxidants and showing their capabilities to prevent deterioration of sunflower oil heated at 60 oC for 24 days in a continuative tool. 3. to evaluate the proximate chemical analyses of the agro-industrial wastes under the study. Data in this study revealed that: A. Proximate chemical composition: 1. The chemical analyses of the waste samples showed that the peanut skin had the highest value of dry matter 95% followed by chickpea hull 91.6% then broad bean (Faba bean) hull 90% whereas the lowest one was found in banana peel 9%. 1*5 *7 2. Pea pod was having the highest value of protein (15.1%) followed by peanut skin (13.5%) then eggplant peel (11.6%) whilst guava leaves contained the lowest value (2.2%) . 3. Peanut skin had (6.2%) fat followed by banana peel 4.8% then orange peel 3% whereas potato peel had the lowest value (0.2%). 4. The ash in the waste samples under this study ranged between 2.25% to 16.3%. The highest value was determined in banana peel 16.3 % followed by prickly pear peel then chickpea hull. The lowest ash content was recorded for peanut skin 2.25%. 5. The crude fiber was differed significantly and ranged between 46% in banana peel to 25.6% in potato peel. 6. The highest value of carbohydrates by difference was found in pomegranate peel 62.9% followed by potato peel 60.6% till reached to the lowest value in banana peel 27.4% . B. Total phenolic compounds: 1. The phenolic compounds were extracted from waste samples under this study using three solvents, methanol, ethanol and acetone; the study revealed that the best solvent was methanol followed by ethanol then acetone. 2. In methanolic extracts peanut skin had the highest total phenolic content (78.36 mg GAE/g DW) followed by mango peel (77.22), pomegranate peel (66.6), guava leaves (52.23), orange peel (50.53) and faba bean hull (38.73), while, eggplant peel had the lowest total phenolic content (4.45 mg equivalent GAE /g DW). 1*5 *8 3. Ethanolic as well as acetonic extracts followed similar trend except that the lowest amount of phenolics was recorded in pea pod, and chickpea hull (4.28 and 5.05 mg equivalent GAE/g DW, respectively). C. Identification and determination of phenolic compounds: 1. Twelve phenolic compounds were identified in most of the agroindustrial waste samples. 2. The numbers and quantities of the phenolic compounds were varied in the different waste samples under study. 3. Comparison among the wastes revealed that: 3.1- Homogentistic acid followed by catechin and Ferulic acid were present in high concentrations, while vanillic acid followed by pcoumaric were present in low concentrations in potato peel. 3.2 - Chlorogenic acid followed by Homogentistic and catechin were present in high concentrations, while ferulic acid followed by pcoumaric were present in low contents in eggplant peel. 3.3 - Homogentistic acid followed by salicylic and catechin were present in high concentrations, while ferulic acid followed by p-coumaric was present in low contents in prickly pear peel. 3.4 - Homogentistic acid followed by catechin and protocatechuic acid were present in high concentrations, while vanillic acid followed by p-coumaric were present in low contents in pomegranate peel. 3.5 - Catechin followed by ellagic acid and chlorogenic acid were present in high concentrations, while Me – protocatechuic acid 1*5 *9 followed by caffeic acid were present in low contents in banana peel . 3.6 - Chlorogenic acid followed by salicylic acid and catechin were present in high concentrations , while ferulic acid followed by gallic acid were present in low contents in mango peels . 3.7 - Ferulic acid followed by Me – protocatechuic acid and gallic acid were present in high concentrations, while caffeic acid followed by vanillic acid were present in low contents in orange peel. 3.8 - Catechin followed by protocatechuic acid and Me-protocatechuic acid were present in high concentrations , while vanillic and pcoumaric acids were present in low contents in pesnut hull . 3.9 - Ellagic acid followed by homogentisic acid and catechin were present in high concentrations, while ferulic acid followed by pcoumaric acid were present in low contents in pea pod. 3.10 - Salicyle acid followed by caffeic acid and ellagic acid were present in high concentrations, while gallic acid followed by p-coummaric were present in low contents in faba bean hull. 3.11 - Caffeic acid followed by Me –protocatechuic acid and catechin as well as gallic acid were present in high concentrations, while ferulic acid followed by p- coumaric acid as well as vanillic acid were present in low contents in chickpea hull . 3.12 - Chlorogenic acid followed by catechin and salicylic acid were present in high concentrations, while p-coumaric followed by vanillic acid were present in low contents in guava leaves. 1*6 *0 D. Antioxidant activity: 1. The effect of waste sample methanol extracts as antioxidants was estimated with DPPH. Free radical scavenging method. 2. The study showed that the highest value was recorded to guava leaves (66.9%) followed by prickly pear peel (60.81%) then orange peel (53.06%) whereas the lowest value was in eggplant peel 21.32%. E. Oxidation stability of sunflower oil: 1. The oxidation stability of sunflower oil heated at 60oC for 3, 6, 11, 15, 18, 21 and 24 days continuously was studied by adding the different extracts understudy as natural antioxidants at concentration of 200 ppm. BHA was applied at the same concentration. 2. The following parameters were determined on time: Peroxide value, Panisidine, TBA, FFA% and the Totox values. 3. There were gradually increases in the all parameters mentioned above. But it was observed the positive effect of the waste samples as natural antioxidants in reducing the deterioration of sunflower oil under storage condtions. 4. The effect on PV The inhibition % in PV for oil treated with wastes extract ranged between 59-77%. The efficacy of waste extracts and BHA to decrease PVs in oil could be arranging as follows: 1*6 *1 BHA > prickly pear peel ≥ guava leaves > faba bean hull ≥ orange peel > mango peel ≥ pomegranate peel > chickpea hull > potato peel > peanut skin > pea pod > banana peel > eggplant peel > control. 5. The effect on AV The AV of oil with waste extracts was significantly different than control sample (P <0.01). Significant differences were also observed between oils with different wastes at almost all the intervals and the stabilization effect was varied from 56-73% relative to control. The effectiveness of waste extract as natural antioxidants compared to synthetic one along with the control can be arranged in the following descending order: Guava leaves > prickly pear peel > BHA > orange peel > faba bean hull > mango peel > pomegranate peel > chickpea hull ≥ potato peel > pea pod ≥ peanut skin > banana peel > eggplant peel > control 6. The effect on TBAVs The TBAVs in oil with waste extracts were significantly lower than control oil. Significant differences were observed among the oil with waste samples at all intervals. The inhibition of TBA formation was ranged between 46 to 81% relative to control. The efficacy of waste extracts to reduce TBA can be arranged in the following descending order: Guava leaves > BHA > prickly pear peel > mango peel ≥ orange peel ≥ faba bean hull > pomegranate peel > chickpea hull > potato peel > banana peel > pea pod > peanut skin > eggplant peel > control. 1*6 *2 7. The effect on FFA% The efficacy of wastes and BHA to reduce FFA values could be arranged in ascending order as follows: BHA > guava leaves > orange peel > faba bean hull ≥ prickly pear peel > mango peel > pomegranate peel > potato peel > chickpea hull > peanut skin ≥ pea pod > banana peel > eggplant peel > control. 8. The effect on Totox value: Oil mixed with waste extracts and BHA reduced significantly totox value than control. Totox values of oil mixed with prickly pear peel extract followed by guava leaves extract were closet to oil with BHA. The efficiency of waste extract and BHA to reduce totox value could be arranged ascendingly as follows: BHA ≥ prickly pear peel ≥ guava leaves > faba bean hull > orange peel > mango peel > pomegranate peel > chick pea hull > potato peel > peanut skin > pea pod ≥ banana peel > eggplant peel > control. In conclusions, from economic, environmental and health view points, adding value to agro-industrial wastes is always appreciated. Such wastes contain potentially valuable compounds that could be isolated and used to make high-value foods. Based on the results of the current study agro-industrial wastes could be used as a source of crude fiber and phenolic compounds. Extracting the wastes with methanol produced extracts with high phenolic contents which had fair to good antioxidant activity as confirmed by DPPH assay. The phenolic profiles were determined by HPLC and were found to be complex mixtures of hydroxylcinnamic acids, hydroxylbenzoic acids, flavonoid 1*6 *3 and others. Variation in total phenolic content, DPPH radial scavenging activity and individual compounds were noticed between waste samples. In this concern, knowledge on total phenolic content, antioxidant activities and individual phenolics of pea pod and chickepea hull could be the first attempted to report here. The addition of phenolic compound extracted from the wastes in this study; as natural antioxidants; and BHA; as standard antioxidant; at 200 ppm resulted in retardation of oxidative deterioration of sunflower oil during storage under accelerated storage conditions. Guava leaves and prickly peer phenolic extracts were comparable to BHA in protection of sunflower oil against oxidative rancidity. Therefore, it could be recommended them as well as other waste phenolic extracts but at higher concentrations to use as sources of natural antioxidants to be used in oils and fatty foods instead of BHA which might be had toxic and carcinogenic effects on human health as reported in scientific literature. |