الفهرس 
Bioactive components in yoghurtOnly 14 pages are availabe for public view
 |  | from | 99 |  |  |
| | | from | 99 | | |
Abstract
The objectives of this study were to investigate the possibility of making a good quality yoghurt that made from cow’s milk has supplementation with whey protein isolate and whey protein hydrolysate, study the effect of incorporating bifidobacteria on yoghurt that made from cow’s milk has supplementation with whey protein isolate and whey protein hydrolysate quality, investigate the effect of adding whey proteins on the survival of bifidobacteria and the quality of yoghurt, monitor the survival of bifidobacteria and changes of chemical, microbiological, rheological and organoleptic properties during storage of yoghurt and to study the effect of feeding probiotic yoghurt that made from cow’s milk has supplementation with whey protein isolate and whey protein hydrolysate on type 2 diabetic individuals. This study has been carried out in four parts: Part I: Functional properties of whey protein isolate and hydrolysate: Control of the molecular size of resultant peptides constitutes is an essential step in the development of protein hydrolysate for dietary use. However, the degree of variability in composition, functionality and sensory properties of WPC has greatly limited their use in food industry. In this part functional properties of whey protein isolate and whey protein hydrolysate were studied to evaluate the effect of hydrolysis of whey isolate. Therefore, water absorption, fat absorption, Emulsification capacity and foam capacity and stability. The obtained results could be summarized as follow: 1. Hydrolysis of whey protein caused a pronounced increase (p < 0.05) in water absorption capacity. 2. Whey protein hydrolysate exhibited higher fat absorption (p < 0.05) than whey protein isolate. 3. The emulsification capacity reduced significantly (p < 0.05) by enzyme hydrolysis of whey protein. 4. Whey protein hydrolysate exhibited higher foam capacity (p < 0.05) than whey protein isolate. 5. Foam stability of whey protein isolate were higher than whey protein hydrolysate after standing at room temperature for 15 and 30 min. Part II: Effect of supplementing cow’s milk with whey proteins on the quality of yoghurt: Because of the potential health benefits of whey proteins, it has been concerned in this part to study the effect of supplementing cow’s milk with whey proteins on yoghurt quality. Therefore, cow’s milk 3.0% fat was supplemented with 3.0% non-fat dry milk (Dairy America, California, USA). That milk was divided into 9 batches. One batch was served as control yoghurt. Another four batches were supplemented with 0.75, 1.5, 2.25 and 3.0% whey protein isolate (LACPRODAN DI-9224) (T2, T3, T4 and T5, respectively). The other four batches were supplemented with 0.75, 1.5, 2.25 and 3.0% whey protein hydrolysate (LACPRODAN DI-3065) (T6, T7, T8 and T9, respectively). Whey protein isolate (LACPRODAN DI-9224) and whey protein hydrolysate (LACPRODAN DI-3065) were gratefully obtained from Arla ingredients group, Denmark. Non-fat dry milk, whey protein isolate and whey protein hydrolysate were added to milk and stirred thoroughly, then filtered through cheese cloth. All treatments were heated to 85°C for 20 min, then cooled to 42°C and inoculated with 1.5% Streptococcus thermophilus and 1.5% Lactobacillus delbrueckii subsp. bulgaricus. The inoculated batches were packed in plastic cups and incubated at 42°C for 3.0 – 3.5 hrs. until complete coagulation. All yoghurt treatments were stored in refrigerator (6°C + 1) for 12 days and were sampled when fresh and at 3, 6, 9 and 12 days for chemical, rheological analysis and sensory evaluation. The whole experiment was triplicated. The obtained results could be summarized as follow: 1. Supplementing cow’s milk with whey proteins used to make yoghurt has no significant changes in acidity and there were no significant differences in acidity among yoghurt treatments made with whey protein isolate and corresponding yoghurt treatments those made whey protein by adding whey protein hydrolysate. Acidity of all yoghurt increased as storage progressed. On the other hand, pH values as affected by storage period followed an opposite trends to acidity. 2. Adding whey proteins to cow’s milk yoghurt increased significantly the total solids content. Total solids content of all yoghurt treatments did not change significantly during storage period. 3. Adding whey proteins to cow’s milk yoghurt treatments significantly different in ash and protein contents. Also, protein and ash contents of all yoghurt treatment did not change significantly during storage period. Adding whey protein isolate and hydrolysate increased values of ash and total protein content. 4. Diacetyl and acetyl methyl carbinol (DA + AMC) increased in all yoghurt treatments up to the sixth day of storage then decreased up to the end of storage period. Yoghurt treatments made with adding whey protein hydrolysate contained higher diacetyl and acetyl methyl carbinol content than corresponding yoghurt treatments those made with whey protein isolate. 5. Total volatile fatty acids (TVFA) of all yoghurt treatments increased as storage period progressed. Adding whey proteins hydrolysate caused a significant increase in TVFA more than whey protein isolate, and this increase was proportional to the amount added of whey proteins. 6. Whey syneresis of all yoghurt treatments decreased gradually during storage up to the sixth day of storage period, and then increased as storage period progressed. There were negative correlations between whey syneresis and the rate of adding whey proteins. 7. Supplementation of cow’s milk with either whey protein isolate or whey protein hydrolysate increased the curd tension of yoghurt treatments. Curd tension increased by increasing the rate of adding whey protein. Yoghurt treatments made with whey protein isolate were not significantly different from those of corresponding yoghurt treatments made with whey protein hydrolysate. 8. The type of whey proteins did not affect significantly the scores of organoleptic properties of yoghurt treatments. Total scores of organoleptic properties increased by increasing the rate of supplementation with whey proteins. On the other hand organoleptic scores of all yoghurt treatments did not change significantly (p > 0.05) up to the sixth day of storage period, then decreased as storage period progressed. from these results, it can be concluded that treatments made with adding 3% of whey protein isolate and hydrolysate were the most acceptable treatments and were not different from control yoghurt treatments. Part III: The effect of adding whey proteins on the survival of bifidobacteria and their effect on the quality of probiotic yoghurt: Because of the potential health benefits of bifidobacteria in improving intestinal health and insulin secretion therefore glucose control. It has been concerned in this part to study the effect of replacing normal yoghurt starter partially with bifidobacteria on yoghurt quality and to monitor the viability of bifidobacteria during cold storage. In this part of the study it was concerned to study the effect of adding whey proteins on the survival of bifidobacteria, chemical, rheological and organoleptic properties of probiotic yoghurt that made from cow’s milk supplemented with whey proteins. Five yoghurt treatments were made from 3.0% fat cow’s milk supplemented with 3.0% non-fat dry milk. This milk was divided in to five batches. Control yoghurt was made by inoculating 1.0% normal starter (NS) and 2.0% of Bifidobacterium longum ATCC 15707 (T1). Cow’s milk was supplemented with 3.0% whey protein isolate and whey protein hydrolysate to make the other four treatments. Two of them were made without adding Bifidobacterium longum ATCC 15707. Two yoghurt treatments were made from cow’s milk supplemented with whey protein isolate and hydrolysate and inoculated by 3% normal starter (NS) (T2, T4). The other two treatments were made as described above except that 1.0% normal starter and 2.0% Bifidobacterium longum ATCC 15707 were added individually (T3, T5). All yoghurt treatments were made, stored for 12 days and sampled at 1, 3, 6, 9 and 12 days for sensory evaluation, chemical and rheological analysis and counting bifidobacteria. The experiment was triplicated. The obtained results could be summarized as follow: 1. Counts of bifidobacteria increased in yoghurt treatments up to the 3rd day then decreased, as storage period proceeded. All samples exhibited counts higher than should be present to achieve the health benefits of bifidobacteria. It could be observed that adding whey protein hydrolysate affected significantly the survival of bifidobacteria more than corresponding yoghurt treatments made with adding whey protein isolate. 2. Counts of total bacteria increased during the first 3 days of storage period then decreased as storage period advanced. These counts decreased by incorporating bifidobacteria when compared with corresponding yoghurt treatments made without adding bifidobacteria. 3. Moulds and yeasts were not detected during the first 9 days of storage, then appeared and increased as storage period progressed in all yoghurt treatments. Incorporation of bifidobacteria decreased the counts of mould and yeasts. 4. Adding bifidobacteria decreased whey syneresis in yoghurt treatments that made from cow’s milk supplemented with whey proteins(T3 and T5) when compared with yoghurt treatments those made without adding bifidobacteria. 5. Adding bifidobacteria to yoghurt made from cow’s milk supplemented with whey proteins did not affect significantly curd tension. 6. Incorporating bifidobacteria caused a significant decrease in acidity when compared with corresponding yoghurt treatments made without adding bifidobacteria. 7. Incorporating bifidobacteria did not affect significantly fat, protein, ash and total solids. Neither bifidobacteria nor storage period affected fat, protein, ash and total solids in yoghurt treatments. 8. Diacetyl and acetyl methyl carbinol (DA + AMC) increased in all yoghurt treatments up to the sixth day of storage then decreased up to the end of storage period. Incorporation of bifidobacteria caused a significant increase in DA + AMC. 9. Total volatile fatty acids (TVFA) of all yoghurt treatments increased as storage period progressed. Incorporation of bifidobacteria caused a significant increase in TVFA. 10. Fresh control yoghurt treatments gained the highest scores of organoleptic properties. Scores of treatments made by adding bifidobacteria increased slightly up to the sixth day of storage then decreased slightly. Scores of organoleptic properties of all yoghurt treatments did not change significantly up to the sixth day of storage period then decreased. Part IV: Effect of feeding probiotic yoghurt that made from cow’s milk supplemented with whey protein isolate and whey protein hydrolysate on diabetic subjects: In the fourth experiment 3 yoghurt treatments, one of them is the control was made from cow’s milk supplemented with 3.0% nonfat dry milk inoculated by 3.0% normal starter. The other two treatments were made from cow’s milk supplemented with whey protein isolate and hydrolysate and were inoculated by 1% normal starter (NS) and 2% Bifidobacterium longum ATCC 15707. Resultant yoghurt will be used to feed adult type 2 diabetes mellitus. Grouping subjects: The experiment was carried on 15 patients, which divided into 3 groups each one contains 5 subjects. Each group were asked to made analysis before and after the experiment. 1. The first one included diabetic subjects before consuming ordinary yoghurt. 2. The second one included diabetic subjects after consuming ordinary yoghurt. 3. The third group included diabetic patients before consuming WPI yoghurt. 4. The fourth group included diabetic patients after consuming WPI yoghurt. 5. Fifth group included diabetic patients before consuming WPH yoghurt. 6. Sixth group included diabetic patients after consuming WPH yoghurt. Patients asked to follow the diet and yoghurt for 8 weeks. Stool samples were collected for microbiological analysis. At the end of the experimental period they were asked to give blood and urine samples. Samples were collected then centrifuged for collection the serum then stored at -20°C until analysis. Blood samples which collected to evaluate postprandial insulin were collected and added to anti-coagulated substances E.D.T.A. to evaluate the following indicators: Fasting and postprandial glucose, postprandial insulin, liver enzyme (GOT, GPT), Serum Total Lipids (T.L, T.G, TC, HDLc, LDLc and VLDLc) and Kidney functions (Urea, Creatinine). Statistical Analysis were performed by using computer program statistical package for social science (SPSS) and compared with each other using the suitable tests. The obtained results could be summarized as follow: 1. Microbiological analysis: stool samples were collected to evaluate the bifidobacteria count on all groups before and after trial. All groups fed on probiotic yoghurt had higher numbers than other groups. All groups before trial had low numbers of bifidobacteria. 2. Fasting and postprandial glucose: the highest group was the ordinary yoghurt one, but WPI and WPH yoghurt have the lowest values. All yoghurt treatments has an effect on glucose levels. 3. Postprandial insulin: the lowest concentration was ordinary yoghurt then the WPI and the best one was WPH. 4. Cholesterol: the groups of WPI and WPH yoghurt have the lowest cholesterol level compared with ordinary yoghurt group. 5. Liver Enzymes: - S.GOT: there were no significant differences between groups in GOT before the experiment. But after consuming bifidobacteria yoghurt made with whey protein isolate and hydrolysate, it was observed significant decrease in SGOT values. - S.GPT: ordinary yoghurt was the highest one but the WPI and WPH yoghurt were the lowest one. There were significant decrease when compared with ordinary yoghurt group. 6. Kidney functions: - S. Urea: the values of all treatment groups with bifidobacteria yoghurt made with adding whey protein isolate and hydrolysate were reached to the normal references, and decreased more than ordinary yoghurt group. - S. Creatinine: the Creatinine values were slightly different with significant level and it reached closely to normal references, but whey protein hydrolysate bifidobacteria yoghurt group has a significant decrease in creatinine values. 7. Pre- and post-meal plasma glucose concentration: it was obvious that consuming probiotic yoghurt made with whey proteins results in post-meal glucose control in healthy and diabetic patients when compared with ordinary yoghurt.