الفهرس 
Bioactive compoundsOnly 14 pages are availabe for public view
Abstract
The aims of this study were to examine the influence of extraction media and conditions on extractability of bioactive compounds from some fruit and vegetable peels . The antioxidant and antimicrobial activities of different peels extracted were also evaluated. In addition the potential application of the most effective peels extracts as source of natural antioxidant and antimicrobial agents were investigated in some food products. The obtained results can be summarized as follows 5.1.Chemical composition of the selected fruit and vegetable peels Peels of pomegranate, mango , prickly-pear , cantaloupe and pea represented 52.4, 15.2, 50.7, 28.6 and 52% of the total weight of the fruits respectively. Pea peel (PeP) contained the highest moisture content (72.45%) and the lowest carbohydrate content (12.24%) , while cantaloupe peel (CaP) showed the highest contents of protein (18.02%) and carbohydrate (40.57%) and the lowest content of fat (1.14%) . On the other hand, pomegranate peel (PoP) recorded the highest fat content (6.05%), and prickly pear (PrP) showed the lowest content of protein (9.45%) and ash (0.54). 5.2. Extraction and evaluation of bioactive compounds from fruit and vegetable peels. 5.2.1. Extraction yield Results showed that the extraction yield % of different peels extracts using solvents with different polarity was presented in the following order PoP> MaP>PrP>PeP≈CaP Depending on the solvent system, it appears that ethanolic extracts significantly showed the highest yield % from PoP , MaP and PrP (50.37, 40.57 and 33.86 % resp.) , while water extract exhibited the most yield from CaP and PeP (20.21 and 25.05%). 5.2.2. Total phenolic and flavoniod contents of different peels extracts Total phenolic (TP) and flavonoids (TF) contents of different peels extracts were significantly (P<0.05) differed depending on the peel source and solvent system. Ethanolic extracts of PoP, MaP and PrP significantly recorded higher TP content (93.77, 181.65 and 61.62 mg GAE /g respect.) than other tested extracts. Oppositly, water extract of CaP and PeP significantly extracted more TP contents (33.64 and 48.45 mg GAE /g) when compared with other tested solvents. However, ethanolic extracts of PoP and MaP had the highest amount of TF (17.57 and 14.71 mg catachine/g), while it was the mixture of ethanol, methanol and ethyl acetate in the case PrP (1.25 mg catachine/g). On the contarary, water was found to be the better solvent for extracting TF from CaP and PeP (8.82 and 7.08 mg catachine /g). 5.2.3. Antioxidant activity of different peels extracts Results showed that among all tested solvents, ethanolic extracts of PoP, MaP and PrP significantly exhibited the strongest antioxidant activity measured by ABTS , FRAP and DPPH assays, being 243.05, 357.9 & 257.38 mg Trolox /g PoP , 315.5 ,319.5 &343.02 mg Trolox /g MaP and 199.98 ,222.08 and 209.70 mg Trolox /g PrP respectively. On the other hand aqueous extracts of CaP and PeP had significantly high antioxidant activity by ABTS ,FRAP and DPPH with 182.5 , 215.3 and 200.4 mg Trolox /g CaP and 164.9 , 211.4 and 195.2 mg Trolox /g PeP resp. In conclusion, the antioxidant capacity of different peels extracts was showed the following descending order mango > Pomegranate > Prickly pear (ethanolic extract)> Cantaloupe ≈ Pea (water extract ). 5.2.4. Correlation between antioxidant activity, total phenolic and flavonoid contents A strong linear relationships could be observed between the total phenolics content and antioxidant capacity of different peel extracts (R2= 0.85 ,0.89 and 0.82 for ABTS , FRAP and DPPH values resp.).Also there was a positive linear correlation between the total flavonoids and antioxidant capacity of the peel extracts (R2= 0.71 ,0.82 and 0.61 for ABTS, FRAP and DPPH values resp.) 5.2.5. Effect of extraction time and temperature on antioxidant activity of different peel extracts Results showed that both extraction time (1, 2 and 4h) and temperature (25,40 , 80°C) have significant effect on antioxidant activity values of different peel extracts. It can be seen that extraction temperature had significant (P<0.05) negative effect and extraction time was shown to have a significant positive effect (with the exception of 80°C) on ABTS values of different peels extracts, Based on these results, moderate extraction temperature of 25 ⁰C for 4h was selected to yield high bioactive compounds from different peels extracts in this study. 5.2.6. HPLC analysis of phenolic compounds of different peel extracts Phenolic compounds of ethanolic extracts of PoP, MaP and PrP and aqueous extracts of CaP and PeP were subjected to HPLC analysis to investigate the types of phenolic compounds responsible for their antioxidant and antimicrobial activity.Results showed that gallic acid was identified as the major compounds in MaP (95.04%) and PoP(65.73%) extracts, while it was rutin the case of PrP (83.87%), CaP (64.33%) and PeP (55.4%) extracts. Also, it is clearly noticed that MaP extract exhibited the highest amount of gallic acid (11739.35µg /g) followed by PoP extract (7818.80µg /g) and CaP extract (123.33 µg /g) and it was not detected in the water extract of PrP and PeP. On the other hand, CaP extract contained the most amount of rutin (2007.17µg /g) followed by PrP and PeP extracts (1263.04 and 309.234µg /g resp.) 5.2.7. Antimicrobial activity of different peels extracts The antimicrobial activity of different concentrations of ethanolic extracts of PoP, MaP and PrP and water extracts of CaP and PeP were tested against 6 strains of microorganism . Results showed that ethanolic extract of PoP, MaP and PrP and water extract of PeP at different concentrations were effective against different tested microorganisms, while water extract of CaP was not effective against S.aureus and S. entertidis. Also, the inhibitory of each peel extract was considerably increased by increasing their concentrations . However, at the highest level of PoP extracts (250µg /ml) mean inhibition zones produced were between 16.01 mm (A.niger) and 22.18 mm (S . entertidis) .For instant , the mean inhibition zones of 250µg /ml of MaP were between a low of 13.92 mm for S . entertidis and a high of 24.55 mm for E.coli . Results also revealed that E.coli, B.cereus and C. albicans were the most sensitive microorganismis to the tested peels extracts, with a greater sensitivity to ethanolic extract of MaP ,PoP and PrP than water extract of CaP and PeP. Based on these results, it is possible to conclude that the ethanolic extract of mango and pomegranate peels to had a stronger activity against different tested microorganisms than other investigated extracts. 5.3. Application of different peels extracts in some food products 5.3.1 Production of cup cake For studing the effect of the natural antioxidants and antimicrobial on the quality of cake, Pomegranate (PoP) ,Mango (MaP) , Prickly- pear (PrP), Cantaloupe (CaP) and Pea (PeP) peels extracts were added at different concentrations during the processing of cup cake. 5.3.1.1 Changes of peroxide value (PV), Acid value (AV) and Thibarbitoric acid (TBA): The cup cake after baking stored at room temperature (25 ±5⁰C) for 7, 14 and 21 days. PV,AV and TBA values increased continuosly in all cake samples during storage periods. The increment rate in the values were decreased with increasing of pomegranate (PoP) ,Mango (MaP) , Prickly- pear (PrP), Cantaloupe (CaP) and Pea (PeP) extracts from 400 to 800 ppm. The increases were considerably higher in control cup cake sample compared to other samples in which synthetic antioxidant , butylated hydroxy toluene (BHT) or natural antioxidants incorporated .Also,it is observed that AV of oil samples containing CaP extract at 800 ppm or BHT at 200ppm had the leaset AV in comparison with other samples or control.Addition of PoP , MaP , PrP , CaP and PeP extracts at different levels (400,600 and 800 ppm) reduced TBA values compared to the control sample throughout the storage period. 5.3.1.2. Microbiological quality of cup cake A little reduction of total bacterial counts was occurred among the cake samples containing PoP , MaP ,PrP ,CaP and PeP extracts or the sample containing sorbate potassium compared to the control ,but the control cup cake sample showed the higher counts during storage period . On the other hand, the bacterial counts were not detected in cup cake samples containing 800ppm of PoP or MaP peel extracts at fourteenth days storage.Also from the data, molds and yeast in cup cake samples were not detected in all samples as initial time of storage, also were not detected in cake samples containing 600 or 800 ppm of PoP extract at 7,14 and 21 days of storage. 5.3.1.3. Sensory evaluation of cup cake Regarding taste acceptance, most of tested samples were acceptable for the panelists, except the samples containing higher concentrations of PoP, MaP, Prp, CaP and PeP extracts. On the other hand ,there was no significant differences between control cake samples and cake samples containing synthetic antimicrobial (sorbate potassium) or PoP, MaP, PrP, CaP and PeP extracts at levels 400,600 and 800 ppm in both appearance ,flavor and color , except the cup cake containing 800 ppm Cap peel extract was significantly different as compared with the other samples. Generally it could be concluded that ,bioactive compounds extracted from PoP , MaP ,PrP ,CaP and PeP showed strong antioxidants activity and effective antimicrobial properties when compared with the synthetic antioxidant or antimicrobial during storage cake for 21 days. 5.3.2 Thermal stability of sun flower oil by using deep frying: The effect of PoP, MaP, PrP, CaP and PeP extracts on the stability of sunflower oil during deep frying (180± 5◦C/ 10 min) were studied as a measureof PV, AV and TBA values. Generally (Pv, Av and TBA ) values of control sample was very high than other samples under investigation during the three cycle of frying. PV of control sample increased from 1.8 at zero time to 18 mg peroxide /kg oil for the third frying cycle. Also TBA increased from 0.8 to 3.2 mg manolaldhyde/kg and AV from 1.6 to 3.0 mg FF / Kg oil for control sample after thierd frying. from the obtained data , PV show a little decrease by increasing the levels of extracted from 300 to 700 ppm, PV decreased from 3.0 to 1.9 and from 2.1 to 1.5 mq peroxide/ Kg oil for the first frying cycle when added PoP and MaP peel extracts , respectively. The same trend was also noticed for second and third frying cycle . On the other hand , an increase in acid value was observed in all the samples . The increase was higher in the control sample than sample containing BHT or PoP, MaP, PrP, CaP and PeP extracts at different levels. Also, AV show a little decrease by increasing the level of extracted from 300 to 700 ppm . TBA content in stripped sunflower oil samples containing different concentration of PoP , MaP ,PrP ,CaP and PeP extracts were low than the control and the sample containing the reference antioxidant (BHT). Generally, natural antioxidants from PoP, MaP, PrP, CaP and PeP extracts exhibited strong antioxidant activity during frying and the level of stabilization is even superior to that BHT. Therefore it can be concluded that pomegranate, mango peel extracts can be used to stabilize sunflower oil against oxidation.