الفهرس 
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Abstract
Functional foods have positive effects on consumer health as well as nutritional value. Increasing consumer interest in maintaining health and has led to the development of many new functional dairy products that contain many functional ingredients that reduce cholesterol uptake, can significantly reduce blood pressure and play a role in regulating satiety, metabolic disorders associated with obesity, and antimicrobial effects may occur.
Labneh is one of the most famous dairy products in different parts of the world, especially in the Middle East, where it plays an important role in food systems. Its outstanding food benefits and conservation characteristics have increased its economic importance. Therefore, the aim of this study was to develop and evaluate the quality of the functional labneh using various functional fats and protein sources with the presence of probiotic bacteria. To achieve this aim, the study was designed in four main parts as follows:
Part I: Development and quality assessment of labneh with probiotic cultures
The objective of this part was to assess the quality of labneh with different cultures including YCX-11 (Lb. delbrueckii ssp. bulgaricus and St. thermophilus), ABT–7(Lb. acidophilus, Bb. animalis subsp. lactis and St. thermophilus) and L. casei 431 (Lactobacillus paracasei subsp. paracasei). The physiochemical, rheological and bacteriological quality were assessed in triplicate samples during refrigerated storage for 30 days. The fresh samples were sensory evaluated.
1. Physiochemical properties
The results indicated an obvious increase in total solids during the refrigerated storage).
In comparison to the initial total solids, the maximum increase was identified in labneh manufactured with ABT and L. casei 431cultures.
The maximum total solids after 30 days storage was identified in the labneh manufactured with regular yoghurt and L. casei 431cultures.
Fat in dry matter ratios (F/DM %) were slightly decreased in all treatments during the storage period. The regular labneh (control) showed F/DM % stability during the storage period. The maximum decrease in F/DM % was observed in labneh manufactured with ABT and L. casei 431cultures. Contrary, the protein content %, significantly increased in all treatments during the storage period. the maximum protein content % was identified in labneh manufactured with ABT and L. casei 431cultures after 30-day storage.
Acidity is an important criterion when assessing the shelf life quality of fermented dairy products including labneh. The acidity increased in all labneh treatments throughout the storage period. The acidity increased by around 0.30 % in all treatments.
Contrary to the acidity, the pH values decreased in all labneh during the storage period, especially in the first 15 days. The maximum change in pH values were observed in labneh with L. casei 431 culture
The results indicated that acidity associated with wheying off (moisture loss) in all labneh treatment. Accordingly, the total solids % and protein content % increased and F/DM decreased as a direct effect of moisture loss during the storage period of labneh.
2.Rheological properties
2.1. Viscosity
The viscosity appeared in different labneh treatments were higher than of control labneh. As a general trend, the viscosity increased in all treatments during the refrigerated storage period. The major increase in viscosity was observed in the first 15 days of storage. The highest viscosity appeared in the probiotic ABT labneh, followed by probiotic ABT labneh with additional L. casei 431culture.
2.2. Texture profile analysis
The results indicated a varied increase in hardness among all treatments during the storage period. The major increase was achieved in the first 15 days of storage. Slight additional increases were determined in the second 15 days of storage. The highest hardness value was determined in ABT probiotic labneh, followed when L. casei 431 was used with ABT culture.
The results indicated decreased adhesiveness during the refrigerated storage period. The highest initial and final values were determined in probiotic ABT labneh. When L. casei 431 was used with ABT culture, an obvious decrease in adhesiveness was observed. The adhesiveness values determined in regular labneh (control) is comparable to the same labneh with L. casei 431culture.
The results indicated a slight increase in springiness throughout the storage period, especially, when Lb. paracasei subsp. paracasei was used with probiotic ABT and regular cultures.
It can be noticed that cohesiveness values decreased during the storage period. the major decrease was observed within the first 15 days of storage. Cohesiveness values determined for regular labneh (control) is higher than all other labneh. A slight decrease in cohesiveness values was determined when L. casei 431 culture was used with regular labneh.
The results of gumminess and chewiness indicated a remarkable decrease in all labneh trials throughout the storage period. The highest values were determined for probiotic ABT labneh. It is observed that L. casei 431 culture has a decreasing effect when used with ABT culture. The values determined when L. casei 431 culture is used with regular labneh showed no effect on gumminess.
2. Culture viability
The results indicated a decrease in viability for all bacterial cultures within two logarithmic cycles. All cultures exceeded the minimum count required by yoghurt standards (one million viable cells per gram). The final count of Lb. acidophilus in labneh manufactured with probiotic ABT culture was the minimum among all bacterial cultures. All cultures had initial counts more than 108 – 109 cfu/g and final counts more than 107 -108cfu/ g after 30-day storage, except Lb. acidophilus, which had a final count decreased to 3.43 x10⁶cfu/g in labneh manufactured with probiotic ABT culture. An enhanced viability of Lb. delbrueckii ssp. bulgaricus was observed in labneh manufactured with regular and L. casei 431cultures.
The viability of St. thermophilus slightly increased in treatments with L. casei 431 culture . In the same trend, an obvious enhancement in the viability of Lb. acidophilus was identified in probiotic labneh manufactured with both ABT and L. casei 431cultures. Contrary, a decreased viability of Bifidobacterium animalis subsp. lactis was observed in the same labneh. The initial and final counts of Lb. paracasei subsp. paracasei indicated better growth and viability when used with ABT culture
These results indicated an enhanced viability in probiotic labneh manufactured with ABT and L. casei 431 cultures.
4. Sensory evaluation
The probiotic labneh manufactured with ABT and L. casei 431 cultures gained the highest score for appearance, texture, and flavor with a total score of 95.40 out of 100 points. On the other hand, T1 gained the least score of appearance, texture, and flavor with a total score of 93.20 points. Therefore, the best sensory properties among treatments and control are of T3, where Lb. acidophilus, Bifidobacterium animalis subsp. lactis, St. thermophilus, and Lactobacillus paracasei subsp. paracasei were used.
PART II: Development and quality assessment of labneh with functional vegetable Oils.
The objective of this part was to assess the effect of milk fat substitution with some functional oils, including sesame, olive, and flaxseed oils at different levels (50 or 100 %) on physiochemical, bacteriological, rheological and sensory properties of labneh. The physiochemical, rheological and bacteriological quality were assessed in triplicate samples during refrigerated storage for 30 days. The fresh samples were sensory evaluated.
1. Physiochemical properties
The results indicated that labneh with 100 % flaxseed oil had the highest TS content (27.00%), followed by labneh with 100 % olive oil (25.60%). The least TS was obtained for labneh with 100 % sesame oil (24.40%), which is comparable to control labneh (25.80%).
Similar trends were obtained throughout the rest of the storage period (15 and 30 days).
Also, the results indicated that protein content increased throughout the storage period. Labneh with a substitution level of 100% flaxseed oil had the highest protein content (11.22%), followed by labneh with 50% flaxseed oil (11.20%). The least protein content was determined in labneh with 100% sesame oil and 100% olive oil (11.00%).
Acidity values of labneh with different functional oils increased throughout the storage period. Labneh with 50 % flaxseed oil had the highest acidity value (0.62%), while the least was determined in labneh with 50 % sesame oil at 30 days of storage. Labneh with 50% olive oil had the highest value (0.93%), while Labneh with 100% flaxseed and 50% sesame oils had the least value (0.90%).
Contrary, pH values in labneh decreased throughout the storage
period. Labneh with 100% flaxseed or olive oils had the highest value (4.35), while Labneh with 50 % flaxseed oil had the least value (4.25). At 30 days of storage, labneh with 50% olive oil had the least pH value (3.98).
2. Rheological properties
2.1. Viscosity
Labneh with S50 had the highest value while S100 and F 100 had the least value. The same result after 30 days. The viscosity of labneh was increased during storage.
2.2. Texture profile analysis
Hardness varied but increased among all substitution treatments throughout the refrigerated storage period. Labneh with milk fat substituted totally with olive oil exhibited the highest hardness values, while labneh with the 50 of substitution with flaxseed oil had the least values. The same trends were observed throughout the storage period.
Adhesiveness decreased throughout the refrigerated storage period. the highest value was determined in labneh with 100 % olive oil. The least was observed in labneh with 50 % sesame oil. The same trends were measured throughout the storage period.
Springiness slightly increased throughout the storage period. Labneh with 100% olive oil had the highest value, while labneh with 50% flaxseed oil had the least value. After 30 days, labneh with 100 % flaxseed oil achieved the highest value, while labneh with 50% flaxseed oil observed with the least value.
It can be noticed that cohesiveness values decreased throughout the storage period. Labneh with 100 flaxseed oil had the highest value, while labneh with 50% sesame oil had the least cohesiveness values. After 30 days of refrigerated storage, labneh with 50 % sesame oil had the highest value, while labneh with 50 % olive oil had the least cohesiveness values.
Gumminess and Chewiness decreased during the storage period. Labneh with 100% sesame oil had the least value while labneh with 100 olive oil had the highest value. The same trends continued up to the end of the storage period.
3. Culture viability
In general, the viability decreased throughout the storage period. The results obtained for Lb. delbrueckii ssp. bulgaricus indicated that labneh with 100% olive oil had the highest counts, while labneh with 100% flaxseed oil had the least counts. The same trend continued up to 30 days. The maximum growth and viability for St. thermophilus were determined in labneh with 50% flaxseed oil, while the minimum counts
were determined in Labneh with 50% sesame oil while. Labneh with fully substituted milk fat with sesame oil recorded the least viability for the same microorganism after 30 days of storage.
4. Sensory evaluation
The results indicated that labneh with 50% sesame oil gained
the highest total sensory score (94.75%), while labneh with 100 % flaxseed oil gained the least sensory evaluation score (81.25%). Labneh with 50 sesame oil was much better in flavor, body, texture, and appearance compared to the control labneh
PART III: Development and quality assessment of labneh substituted with functional proteins.
The objective of this part was to assess the effect of milk protein substitution with some functional proteins, including sesame, chickpea, and soybean proteins at different levels (15%, 25%, 35%, 50%) on
physiochemical, bacteriological, rheological and sensory properties of labneh. The physiochemical, rheological and bacteriological quality were assessed in triplicate samples during refrigerated storage for 30 days. The fresh samples were sensory evaluated.
1. Physiochemical properties
In comparison to the initial total solids, the maximum increase was identified in labneh manufactured with chickpea 50% throughout refrigerated storage for 30 days.
Fat in dry matter ratios (F/DM %) were slightly decreased in all treatments during the storage period. The maximum decrease in F/DM % was observed in control labneh.
Contrary, the protein content %, significantly increased in all treatments during the storage period. the maximum protein content was identified in labneh substituted with chickpea 50% after 30 days of storage. The protein contents of various labneh treatments slightly increased, which could be ascribed to moisture loss during storage
Acidity is an important criterion when assessing the shelf life quality of fermented dairy products including labneh. The acidity increased in all labneh treatments throughout the storage period. The acidity increased by around 0.30 % in all treatments.
Contrary to the acidity, the pH values decreased in all labneh during the storage period, especially in the first 15 days. The maximum change in pH values was observed in control and labneh substituted with chickpea 50 %.
The results indicated that acidity associated with wheying off (moisture lose) in all labneh treatment. Accordingly, the total solids % and protein content % increased and F/DM decreased as a direct effect of moisture loses during the storage period of labneh.
The results indicated an increase in total solids during the refrigerated storage (30 days). In comparison to the initial total solids, the maximum increase was identified in labneh substituted with 50% soybean protein (S50). The maximum total solids after 30 days of storage were identified in labneh substituted with 50% soybean protein (S50).
Fat in dry matter ratios (F/DM %) were slightly decreased in all treatments during the storage period. The maximum decrease in F/DM % was observed in labneh substituted with 25 % soybean (S25). Contrary, the protein content %, significantly increased in all treatments during the storage period.
The maximum protein content was identified in labneh substituted with 50 % soybean protein after 30 days of storage.
Acidity is an important criterion when assessing the shelf life quality of fermented dairy products including labneh. The acidity increased in all labneh treatments throughout the storage period.
Contrary to the acidity, the pH values decreased in all labneh during the storage period, especially in the first 15 days. The maximum change in pH values was observed in control and labneh substituted with 25 % soybean protein.
The results indicated that acidity associated with wheying off (moisture loss) in all labneh treatment. Accordingly, the total solids % and protein content % increased and F/DM decreased as a direct effect of moisture loss during the storage period of labneh.
2. Rheological properties
2.1. Viscosity
The viscosity appeared in different treatments of chickpea (C15, C25, C35, and C50) were higher than of control labneh. As a general trend, the viscosity increased in all treatments during the refrigerated storage period. The major increase in viscosity was observed in the first 15 days of storage. The highest viscosity appeared in C50, followed by C35.
Also, the viscosity appeared in different substitutions with soybean protein (S15, S25, S35, and S50) were higher than of control labneh. As a general trend, the viscosity increased in all treatments during the refrigerated storage period. The major increase in viscosity was observed in the first 15 days of storage. The highest viscosity appeared similarly in S35 and S50.
2.2. Texture profile analysis
The results indicated a varied increase in hardness among all treatments during the storage period. The major increase was achieved in the first 15 days of storage. Slight additional increases were determined in the second 15 days of storage. The highest hardness value in labneh substituted with chickpea protein was determined in C15, followed by C25. In labneh substituted with soybean protein,
The highest hardness value was determined in S15, after control labneh.
The results indicated decreased adhesiveness during the refrigerated storage period. The highest initial and final values when
substitution with chickpea protein was determined in C25. In labneh substituted with soybean protein, the highest initial and final values were determined in S35.
The results indicated a slight decrease in springiness throughout the storage period for all treatments except control labneh, which increased. C25 labneh had the highest springiness values after control labneh in case of substitution with chickpea protein. S15 labneh had the highest springiness values among all labneh substituted with soybean protein.
It can be noticed that cohesiveness values decreased during the storage period. The major decrease was observed within the first 15 days of storage. Cohesiveness values determined for regular labneh (control) was higher than all other labneh followed by C25 in case of chickpea and S15 in case of soybean protein substitutions.
The results of gumminess and chewiness indicated a remarkable decrease in all labneh trials throughout the storage period. The highest values were determined for C25 in case of chickpea protein substitution, followed by S35 among labneh substituted with soybean protein.
3. Culture viability
The results indicated a decrease in viability for all bacterial cultures within two logarithmic cycles. All cultures exceeded the minimum count required by yoghurt standards (one million viable cells per gram).
All cultures had initial counts more than 10⁷ – 109 cfu/g. An enhanced viability of Lb. delbrueckii ssp. bulgaricus has observed in labneh substituted with 50 % chickpea protein(C50), which decreased to 8.37x10⁵ cfu/g. In case of substitution with soybean protein, the counts decreased to 7.63 x10⁵ cfu/g. The initial and final counts of Lb. delbrueckii ssp. bulgaricus indicated better growth and viability in C15 and S35. A decreased viability of St. thermophilus was observed in all treatments except C50, which increased slightly during 15 days and decreased after 30 days. The initial and final counts of St. thermophilus indicated better growth and viability in C15 and S50 labneh.
These results indicated an enhanced viability in labneh substituted with functional proteins.
4. Sensory evaluation
C15 and C25 labneh gained the highest score for appearance, texture, and flavor with a total score of 98.60 and 98.20 out of 100 points. On the other hand, C50 gained the least score of appearance, texture, and flavor with a total score of 84.40 points. Therefore, the best sensory properties among labneh substituted with chickpea protein was till C25%.
The results indicated that S15 and S25 labneh gained the highest score for appearance, texture, and flavor with a total score of 97.99 and 97.62 out of 100 points. On the other hand, S50 labneh gained the least score of appearance, texture, and flavor with a total score of 78.66 points. Therefore, the best sensory properties among labneh substituted with soybean protein were till S15 and S25 labneh.
PART IV: Development and quality assessment of Functional Labneh with probiotic cultures, Functional Oils, and Proteins
The objective of this part of the study was to assess the combined effects of bacterial culture, oil and protein substitution on quality properties of labneh. Based on the best results achieved in the previous three parts, two labneh trials were manufactured with ABT and L casei 431 cultures, 50 % of milk fat replaced with sesame oil; and 25 % of milk protein replaced with chickpea protein or soybean protein. The physiochemical, rheological and bacteriological quality were assessed in triplicate samples during refrigerated storage for 30 days. The fresh samples were sensory evaluated.
1. Physiochemical properties
The results indicated an obvious increase in total solids during the refrigerated storage (30 days), which ranged between 26.50 % - 27.33 %. In comparison to the initial total solids, the increases identified in both S.C.P and S.S.P labneh were higher than identified in control labneh.
Fat in dry matter ratios (F/DM %) were slightly decreased in all treatments during the storage period. The regular labneh (control) showed F/DM % stability during the storage period. The maximum decrease in F/DM % was observed in S.S.P labneh. Contrary, the protein content %, slightly increased in all treatments during the storage period. the maximum protein content was identified in control labneh followed by S.C.
The acidity increased in all labneh treatments throughout the storage
period. The maximum increase was observed in S.S.P labneh.
Contrary to the acidity, the pH values decreased in all labneh during the storage period, especially in the first 15 days. The maximum change in pH values was observed in S.S.P followed similarly by control and S.C.P labneh
2. Rheological properties
2.1. Viscosity
The viscosity appeared in different labneh treatments (S.C.P and S.S.P) were higher than of control labneh. As a general trend, the viscosity increased in all treatments during the refrigerated storage period. The major increase in viscosity was observed in the first 15 days of storage. The highest viscosity appeared in S.C.P labneh 4000 pa.s, followed by S.S.P.
The increase in viscosity during cold storage of fermented dairy products including labneh is attributed to the water binding by milk protein and to the exopolysaccharides produced by bacterial cultures. The
the viscosity of labneh was increased during storage.
2.2. Texture profile analysis
The results indicated a varied increase in hardness among all treatments during the storage period. The major increase was achieved in the first 15 days of storage. Slight additional increases were determined in the second 15 days of storage. The highest hardness value was determined in regular labneh (control), followed by labneh substituted with 25 % chickpea protein, 50% sesame oil inoculated with ABT and L. casei 431 probiotic cultures (S.C.P).
The results indicated decreased adhesiveness during the refrigerated storage period. The highest initial and final values were determined in S.C.P. labneh, while S.S.P labneh had the least value.
The results indicated a slight increase in springiness throughout the storage period, especially, in labneh substituted with 25 % soybean protein with 50% sesame oil, with ABT and L. casei 431 probiotic cultures (S.S.P)
It can be noticed that cohesiveness values decreased during the storage period. the major decrease was observed within the first 15 days of storage. Cohesiveness values determined for regular labneh (control) is higher than all other labneh, which was followed by S.C.P. labneh. A slight decrease in cohesiveness values was determined in all treatments.
The results of gumminess and chewiness indicated a remarkable decrease in all labneh trials throughout the storage period. The highest values were determined for S.C.P. labneh. A decreasing effect was
observed in labneh substituted with 25 % chickpea protein and 50% sesame oil, with ABT and L. casei 431 probiotic cultures; and labneh substituted with 25 % soybean protein and 50% sesame oil, with ABT and L. casei 431 probiotic cultures
3. Culture viability
The results indicated a decrease in viability for all bacterial cultures within two logarithmic cycles. All cultures exceeded the minimum count required by yoghurt standards (one million viable cells per gram).
All cultures had initial counts more than 107– 109 cfu/g and final counts more than 106 -107cfu/ g after 30-day storage. An enhanced viability of Lb. delbrueckii ssp. bulgaricus, Lb. acidophilus, Bifidobacterium animalis subsp. lactis sp., St. thermophilus, and Lactobacillus paracasei subsp. paracasei was observed in all treatments.
The viability of St. thermophilus were higher in control labneh than other treatments. The initial and final counts of Bifidobacterium animalis subsp. lactis, Lb. acidophilus and Lactobacillus paracasei subsp. paracasei indicated better growth and viability in labneh substituted with 25 % soybean protein with 50% sesame oil.
4. Sensory evaluation
The results indicated that labneh substituted with 25 % chickpea protein and 50% sesame oil with ABT and L. casei 431 probiotic culture (S.C.P) gained higher score for appearance, texture, and flavor with a total score of 97.70 out of 100 points, than labneh substituted with 25 % soybean protein (S.S.P). On the other hand, S.C.P labneh gained the least score of appearance, texture, and flavor with a total score of 95.20 points. Therefore, the best sensory properties among treatments were gained for S.C.P labneh.
CONCLUSIONS
This study concludes that the use of ABT-7 culture (Lb. acidophilus, Bifidobacterium animalis subsp. lactis, and St. thermophilus) and L. casei 431 culture (Lactobacillus paracasei subsp. paracasei) together to improve the functional properties of labneh, and in particular culture viability during the shelf life period. It is also possible to substitute milk fat with sesame oil by no more than 50% and substitute the protein with chickpea or soybean proteins by no more than 25% to not negatively affect the sensory properties of the product.
Finally, it is recommended to produce a functional labneh by substituting both milk fat and protein with 50% sesame oil and 25% chickpea protein, with the use of a probiotic culture containing Lb. acidophilus, Bifidobacterium animalis subsp. lactis., St. thermophilus, and Lactobacillus paracasei subsp. paracasei.