الفهرس 
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Abstract
In recent years, the demand for natural antioxidants has been increased mainly because of the adverse effects of synthetic antioxidants, which have been confirmed for their toxicological and carcinogenic effects. Thus, most of the recent investigations have been directed towards the identification of natural antioxidants from various plant sources, which will offer increased consumer acceptability, decreased potential health risks, and can often achieve the same degree of oxidation prevention as Synthetic antioxidants.
Finding good combinations of natural antioxidants and antimicrobials from plant origins has been a hot topic in recent years. Researchers and food industry all share this approach because it reflects consumer preferences. Replacing synthetic antioxidants with natural ones is an excellent idea but requires further investigation. Several factors can affect the antioxidant and antimicrobial activity of these natural plant extracts in the meat system. For example, the concentration and interaction of natural antioxidant or antimicrobial agents with other compounds, pro-oxidant, free radical, and oxygen availability in the meat system will affect their activity.
Therefore, the aim of this study was to evaluate two plants aqueous extracts (oregano, green tea, and their mix) for their phenolic, flavonoid, antioxidant, and antimicrobial potentials. Furthermore, the mix of these two plant extracts with or without ascorbic acid was applied to Sausage with different concentrations (0.25% and 0.5%) compared with negative control and positive controls (BHT, Ascorbic acid). Their impact on shelf life was assessed through chemical, physio-chemical and microbiological analysis through a storage period of 21 days and at 4 °C, to recommend the most appropriate concentration as a natural preservative replacing the artificial preservative (BHT).
The obtained results can be summarized as follow:
The mean values for phenolic content were (101.52, 324.71 and 367.00 mg GAE /g sample) respectively for (oregano, green tea and their mix). The extracts mix showed the highest phenolic content.
The mean values for flavonoid content were (49.96, 105.97 and 122.20 mg catechol/g sample) respectively for (oregano, green tea and their mix). The extracts mix showed the highest flavonoid content.
Results of antioxidant activity represented in the IC50 in DPPH assay and EC50 in reducing power assay which was (21.49, 16.31 and 14.97 μg/ml) and (45.05, 27.93 and 25.71 mg/ml) respectively for (oregano, green tea and their mix). The extracts mix showed the highest antioxidant potentials, while IC50 value for ABTS was (33.42, 17.74 and 13.13 μg/ml) respectively for (oregano, green tea and their mix).
The mix show a remarkable antimicrobial activity with MIC of 12.5, 25, 50, 75mg/ml with the pathogenic strains (E.coli ATCC25922, klebsila pneumonia ATCC700603, Salmonella typhimurium ATCC13311, Staph aureus ATCC25923 and Bacillus cereus ATCC10876) which was higher than the antimicrobial potentials of each extract alone.
So, in conclusion the results showed that the mix has the highest antioxidant and antimicrobial potentials which implies a strong synergistic effect between the two plant extracts. So, the aqueous extract mix was applied as natural preservative in meat products at two concentrations (0.25% and 0.5%) with and without ascorbic acid and compared with negative control and positive controls (BHT, Ascorbic acid) and the pH value, WHC, TBARS, DNPH and microbial load was evaluated through a storage period of 21 days and at 4 °C.
During storage the treatment with aqueous extract mix on Sausage samples showed results superior to that of the synthetic antioxidant with a lower significant change on pH value The pH of negative control was found to be 5.04±0.02 while the pH value of positive control with BHT and Ascorbic acid was found to be 4.89±0.01and 4.50±0.00 respectively the PH value for treatments mix (0.2 and 0.5 %with ascorbic and without) was (4.70, 4.66, 4.42 and 4.38) respectively at zero time with significant different (p<0.05) the reduced acidity of the treated sausage samples could be due to the acidic nature of the ascorbic acid, but during the 21 days of storage there was a significant differences found through the storage periods which reached final pH values of 7.11±0.00 for negative control and 7.06±0.02 and 6.58±0.00 for BHT and Ascorbic acid positive control respectively while the PH value for treatments mix (0.2 and 0.5 %with ascorbic and without) was (6.89, 6.82, 6.11 and 5.95) respectively.
While water holding capacity at zero day there was no significant difference (p<0.05) in WHC between the sausage samples but through the 21days of storage the WHC decreased significantly in the negative control, positive control and mix 0.2 and 0.5% without ascorbic acid the results changed from (95.86, 95.82, 95.83, 95.98 and 96.01%) respectively at zero day to (92.29, 93.01, 93.08, 92.72 and 93.48 %) respectively at 21 days of storage, while in mix 0.2 and 0.5% with ascorbic acid the results changed between day zero and day 21 of storage they changed from (95.99 and 96.08%) respectively at zero day to (94.01 and 94.38%) respectively at 21 days of storage.
While for lipid oxidation TBARs value at zero day there was no significant difference (p<0.05) in TBARS value between the sausage samples but through the 21 days of storage the TBARS value increased significantly in the negative control, two positive controls (BHT and Ascorbic acid) and mix 0.2, 0.5% with and without ascorbic acid the results changed from (0.10, 0.09,0.09, 0.10, 0.08, 0.08,0.09 Mg MDA\ Kg) respectively at zero day to (2.25, 0.78, 0.78, 0.90, 0.74, 0.61, and 0.57 Mg MDA\ Kg) respectively at 21 days of storage
While for protein oxidation the DNBH value At zero day there was no significant difference (p<0.05) in carbonyl contents value between the sausage samples but through the 21 days of storage the carbonyl contents value increased significantly in the negative control, two positive controls (BHT and Ascorbic acid) and mix 0.2, 0.5% with and without ascorbic acid the results changed from (0.83, 0.85,0.86, 0.86, 0.87, 0.83, 0.85 nmol/mg protein) respectively at zero day to (13.15, 11.23, 11.21, 12.99, 9.36, 8.68, and 7.66 nmol/mg protein) respectively at 21 days of storage.
While the TVB-N value at zero day there was significant difference (p<0.05) in TVB-N value between the sausage samples showing the results of negative control, two positive controls (BHT and Ascorbic acid) and mix 0.2, 0.5% with and without ascorbic acid (2.61, 2.83, 2.80, 2.75, 2.74, 2.65, and 2.72 mg/100 g) respectively and at 21 days of storage it increases reaching (27.32, 20.21, 20.14, 25.18, 19.71, 17.63, and 12.87 mg/100 g) respectively.
While for the total bacterial count at zero day there was no significant difference (p<0.05) in bacterial count between the sausage samples but through the 21 days of storage the bacterial count increased significantly in the negative control, two positive controls (BHT and Ascorbic acid) and mix 0.2, 0.5% with and without ascorbic acid results changed from (7x10, 8x10, 5x10, 4x10, 3x10, 3x10 and 2x10 Cfu/g Cfu/g) respectively at zero day to (1.1X108, 2.6X106, 2.2X106, 2X107, 2X105, 1X106 and 1.1X104Cfu/g) respectively at 21 days of storage.
Whereas total coliform count at zero day there was no significant difference (p<0.05) in coliform count between the sausage samples but through the 21 days of storage the coliform count increased significantly in the negative control, two positive controls (BHT and Ascorbic acid) and mix 0.2, 0.5% with and without ascorbic acid results changed from (2x10, 1x10, 3x10, 1x10, 2x10, 1x10 and 1x10 Cfu/g) respectively at zero day but through the 21 days of storage the coliform count increased significantly reaching to (2x10, 1x10, 3x10, 1x10, 2x10, 1x10and 1x10 Cfu/g) respectively at zero day to (1.8X104, 1.9X103, 1.1X103, 2.8X103, 1X103, 1.9X102 and 1x102Cfu/g) respectively at 21 days of storage .
whereas total yeast and mould count at zero day there was no significant difference (p<0.05) in total yeast and mould count between the sausage samples but through the 21 days of storage the count increased significantly in all sausage samples at zero day there was no yeast or mould count but at day 9 in negative control group the count had a result of 2x10 Cfu/g, while the BHT, ascorbic acid goup, mix 0.2%,mix 0.5% show the results of (1.5X102, 1.6X102, 1.1X102 , 1X10 Cfu/g) respectively at 21 days of storage, but the plant extract mix 0.5% with ascorbic acid was able to stabilize this count till day 21 of storage to (1x10 Cfu/g), which show considerable antifungal effect.
The sensory scores of treated sausage and controls are presented in Table (25). The sausage treated with plant extract mix or without extract (PC and NC) gained no a significant difference (P >0.05) in all sensory criteria including appearance, taste, color, flavor, taste and overall acceptability after processing, but there was a significant difference in the overall grade with the highest score for the control negative group and BHT group 7.82 and 7.77 respectively, which considered appositive results as the treatment were acceptable to the consumer.
These findings show that this plant extract mix at the level of 0.5% with and without Ascorbic acid is very effective against lipid and protein oxidation, and a powerful antimicrobial in different meat products and is a promising natural antioxidant and antimicrobial replacing the synthetic preservatives in meat processing. These biological activities could be attributed to phenols present in these plants. Further research is needed for the isolation and identification of individual phenolic compounds in addition to In-Vivo studies that can introduce better understanding of their mechanism of action.