الفهرس 
Skim milk powderOnly 14 pages are availabe for public view
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Abstract
Antioxidants are substances or nutrients in our foods which can prevent or slow the oxidative damage to our body. When our body cells use oxygen, they naturally produce free radicals (by-products) which can cause cells damage. Antioxidants act as ”free radical scavengers” and hence prevention and repair damage done by these free radicals. Health problems such as heart disease, diabetes, cancer are all contributed by oxidative damage.
Phenolic compounds are secondary metabolites synthesized by plants. They posses strong antioxidant activities acting as free radical scavengers, electron or hydrogen donors and strong metal chelators, preventing lipid peroxidation, DNA damage etc. Yoghurt with added antioxidants from natural sources appears to be a convenient food format to satisfy consumer interest in original yoghurt nutrients, beneficial effects of starter cultures, and health benefits of added antioxidants.
from the above-mention, this study planned to prepare low fat stirred yoghurt through supplemented with natural sources of antioxidants such as pomegranate peel and milk thistle seeds. WPC was used for raising the nutritional value of the final product. The previous ingredients were added to reconstituted skim milk powder (12% TS) for manufacturing low fat stirred yoghurt and kept at 5+1oC for 15 days. So, this study includes the following parts:
Pomegranate peel (PP)
There are increasing interests in applying fruit processing wastes as functional food ingredients since they are rich source of dietary fibre, and most of the beneficial bioactive compounds are remained in those by-products. Additionally, waste products like pomegranate peel from processing of agricultural commodities could offer practical and economic sources of natural active antioxidants which could replace the synthetic ones. Pomegranate peel has been shown to possess preventive and attenuating activities against numerous chronic and health/life threatening maladies such as cancer, type 2 diabetes, atherosclerosis and cardiovascular diseases, stomachic, inflammation, fever, bronchitis, diarrhea, dysentery and urinary tract infection.
Hence this work was planned to embody the following: It had been made primary experiments on pomegranate peel which divided into two parts (inside and outside) and whole pomegranate peel and dried by two methods:
3- Oven drying (40oC/48 h.)
4- Solar drying (50o±2C/24h.)
It has been extracted by two types of solvents (water and methanol) and determined the total phenolic content, total flavonoids content and antioxidant activity (DPPH and ABTS) for all extracts.
The obtained results could be summarized as the following:
2- Determination of total phenolic content (TPC)
The TPC of oven drying water extract and methanol extract for PP were 16.34 and 17.78 (mg gallic acid/g) respectively, while it was 14.81 and 14.38 mg gallic acid/g) by using solar energy in the same order.
3. The total flavonoids content (TFC)
The TFC of oven drying water extract and methanol extract for PP were 6.876 and 7.987 (mg gallic acid/g) respectively, while it was 6.864 and 7.969 (mg gallic acid/g) by using solar energy in the same order.7. DPPH-Radical scavenging activity (RSA)
Radical scavenging activity (RSA) of oven drying water extract and methanol extract for PP were 97.214% and 97.94% respectively, while it was 95.045% and 96.924% by using solar energy in the same order.
8. ABTS Radical scavenging activity
ABTS Radical scavenging activity of oven drying water extract and methanol extract for PP were 89.561% and 90.940% respectively, while it was 88.846% and 90.056% by using solar energy in the same order.
9. Chemical composition of whole pomegranate peel (PP)
The whole pomegranate peel (PP) which dried by oven (40oC/48h.) contained 5.2% moisture, 8.2% fat, 29.5% total carbohydrate, 4.1% ash, minerals like K, Na and Fe were 8751, 742 and 39.6 (ppm) respectively.
10. Manufacturing low fat stirred yoghurt supplemented with different conc. of PP extract
In this part different conc. of PP water extract was used (5, 10, 15, 20, 25, 30, and 35%) and supplemented reconstituted skim milk powder (12% TS) with extract and made stirred yoghurt and determined the total phenolic content (TPC), total flavonoids content (TFC), antioxidant activity (DPPH and ABTS), total count of starter bacteria, chemical composition and sensory evaluation of resultant.
e. TPC, TFC and antioxidant activity (DPPH and ABTS)
The mean values of TPC, TFC and antioxidant activity (DPPH and ABTS) increased significantly by increasing the conc. of PPE in yoghurt samples until 25% conc. of PP extract which TPC, TFC and antioxidant activity (DPPH and ABTS) were 8.23, 3.59 mg gallic acid/g respectively while RSA and ABTS were 53.41 and 14.01% respectively, after that any increase in conc. of PPE in yoghurt samples weren‟t significant f. Total counts of starter bacteria (S.thermophilus and L. delbrueckii subsp. bulgaricus)
It’s noticed from results, the total counts of starter S.thermophilus and L. delbrueckii subsp. bulgaricus were slightly decreased with increasing the conc. of PPE in yoghurt samples. S.thermophilus and L. delbrueckii subsp. bulgaricus were 8.80 and 8.32 (log cfu/ml) respectively for 35% PPE compare to control (without PPE) which was 8.85 (log cfu/ml).
g. Chemical composition
There weren‟t significant differences in total solids, protein, fat, lactose, acidity% and pH while ash% increased by increasing PPE in samples.
h. Sensory properties
There weren‟t significantly difference in flavor and consistent until 25% PPE while the appearance and color of control and 5% PPE had highest score followed by other conc. of PPE also there weren‟t significant difference in overall acceptability until 25% conc. of PPE.
It can be concluded from this part
6- The whole pomegranate peel extract (water or methanol extract) had the highest TPC, TFC and antioxidant activity in comparison with inside and outside pomegranate peel extract.
7- Oven drying at (40°C/ 48 h.) for PPs had higher content of TP, TF and antioxidant activity comparably to solar drying.
8- The methanol extract of PP had higher content of TP, TF and antioxidant activity than water extract but water is considered as an environmental friendly solvent and very effective for antioxidant extraction from pomegranate.9- The best conc. of PP was 25% for adding to reconstituted skim milk powder for manufacturing low fat yoghurt in TPC, TFC and antioxidant activity.
10- There were insignificant difference of addition PPE (25%) on the chemical composition and sensory properties of yoghurt samples.
Whey protein concentrate (WPC)
Whey protein concentrate is used for raising the nutrition value of the final product which had many health benefits components by adding different conc. of it (0.25, 0.50, 0.75, 1.00, 1.25 and 1.50 g/100ml) to reconstituted skim milk powder for manufacturing low fat stirred yoghurt.
5- Determination of TPC and antioxidant activity
With increasing WPC conc. increased TPC and antioxidant activity in yoghurt samples until 0.5 (g/100ml) WPC. Total phenolic content (TPC), RSA and ABTS were 3.89 (mg gallic acid/g), 34.93 and 3.40% respectively. Any conc. of WPC added resulted in decrease in TPC and antioxidant activity.
6- Total count of starter bacteria (S.thermophilus and L. delbrueckii subsp. bulgaricus)
Total count of starter bacteria (S.thermophilus and L. delbrueckii subsp. bulgaricus) increased by increasing WPC conc. where S.thermophilus and L. bulgaricus were 9.09 and 8.92 (log cfu/ml) respectively compared to control 8.79 (log cfu/ml).
7- Chemical composition
Total solids, protein, and fat, lactose% increased by increasing WPC while there weren‟t significant differences in titratable acidity and pH values.8- Sensory properties
There were insignificant differences in flavor until 1.00 (g/100ml) of WPC ,while there were significantly differences in body and texture and appearance and color with increasing WPC but there was insignificant difference in overall acceptability until 0.50 (g/100ml) of WPC.
It concluded that:
5. The fortification of low fat stirred yoghurt with 0.5 (g/100ml) WPC had the highest TPC and antioxidant activity (DPPH and ABTS methods).
6. There was insignificant increase on chemical composition values until 0.5 (g/100ml) WPC in yoghurt samples.
7. WPC had stimulation effect on starter bacteria growth.
8. The yoghurt samples fortified with 0.5 (g/100ml) WPC almost had the same scores and had the highest scores in flavor, consistent and appearance compare to other samples.
Milk thistle
Milk thistle or Mary‟s thistle (Silybum marianum L.Gaertn) contains silymarin is the most commonly used for chronic liver disease treatment and strong antioxidant that has been proven to promote liver cell regeneration, reduce blood cholesterol and help prevent cancer.
2. Chemical composition of milk thistle seeds
It contains 8.07% moisture, 23.50% fat, 5.20% ash , 24.20% total carbohydrate and minerals like K, Ca and Na which were 527.924, 424.586, 94.352 (ppm) respectively. Silymarin was 499.75 (mg/g seeds)4- Effect of extraction Temperature on TPC, TFC and antioxidant activity (RSA & ABTS)
It is obvious that, increasing temperature of extraction of MTS increased TPC, TFC and antioxidant activity (RSA and ABTS). Consequently, it is considered 100°C is the best temp. for extraction of milk thistle seeds (MTSE) . TPC and TFC were 15.648 and 4.263 (mg/g) respectively while RSA and ABTS were 89.673 and 94.725% respectively.
5- Manufacturing of low fat stirred yoghurt supplemented with PPE, WPC and different conc. of MTSE and storaged at 5±1o C for 15 days
g. TPC, TFC and antioxidant activity (DPPH and ABTS)
There were marked increases in TPC, TFC and antioxidant activity (DPPH and ABTS) in yoghurt samples supplemented with MTSE, where TPC, TFC and antioxidant activity (DPPH and ABTS) gradually increased by increasing the conc. of MTSE added. During cold storage, TPC, TFC and antioxidant activity (DPPH and ABTS) gradually decreased for all yoghurt samples, but the fortified samples with MTSE still retained more TPC, TFC and antioxidant activity (DPPH and ABTS) along the storage time than control.
h. Determination of the quantity of silymarin (mg/100ml) in fresh low fat stirred yoghurt by HPLC chromatography
The methanolic solutions of low fat stirred yoghurt fortified with 1, 1.5, 2, 2.5, 3, 3.5 and 4% MSTE determined by HPLC as compared to that of standard silymarin . It is clear from data that a little decrease in the amounts of silymarin in yoghurt samples.i. Chemical composition of yoghurt samples
It’s obvious that increasing the concentration of MTSE in yoghurt samples increased in total solids, lactose, fat and protein%, while these were slightly decreased during storage and there was any significant difference during storage in fat% but titratable acidity% decreased with increasing MSTE% and increased during storage while it’s versus in pH.
j. Total counts of S.thermophilus, L. delbrueckii subsp. bulgaricus and mold and yeast
With increasing the MTSE in stirred yoghurt samples S.thermophilus and L. delbrueckii subsp. bulgaricus and molds decreased and this also observed during storage periods. It is noted that there wasn’t any growth or colony of molds in all yoghurt samples with different conc. of MSTE in fresh samples and during storage.
k. Apparent viscosity
There were considerable decreases in the viscosity of yoghurt samples with increasing the conc. of MTSE. Moreover, there were no great differences in the viscosity between different ratios, even control1 (yoghurt without any additives) and control 2 (yoghurt with PPE and WPC) had slightly higher viscosity than the corresponding yoghurt samples with PPE , WPC and MTSE.
l. Sensory evaluation
Yoghurt samples with the different conc. of MTSE were accepted when fresh, while along the cold storage at 5°C for 15 days the sensory scores decreased not only for the MTSE yoghurt but also for the control. The total scores of yoghurt supplemented with MTSE up to 4% and kept at 5°C for 15 days had acceptability.Finally, the results led to modify healthy fermented milk supplemented with PP (by product) to increase antioxidant activity to fight free radicals which responsible and linked to many diseases in the world and WPC to reduce casein consumption (bad for some patients) and milk thistle extract until 4% conc. Natural bioactive compounds in this product may be responsible for its high antiradical activity and play an important role to meet the health. These achieve the multihealthy benefits especially for heptatooxicity (liver damage) persons.