The Effect of Processing Temperatures on the Microstructure and Firmness of Labneh Made from Cow\u27s Milk by the Traditional Method or by Ultrafiltration

The types of Labneh were made from full-fat cow\u27s milk: (a) traditional Labneh was produced by straining cold yoghurt at 7°C in a cloth bag, and (b) UF Labnehs were produced by ultrafiltration (UF) of warm yoghurt at 35°, 40°, 45°, 50°, and 55°C. The UF Labnehs contained 22.7- 23.9% total solids, 7.8-8.3% protein, and 10.6-11.3% fat as compared to 25.3%, 9.1 %, and 11.9%, respectively, intraditional Labneh. Homogenization of the experimental Labneh samples in an ALM homogenizer using the D-170 or D-280 ,heads made the products smoother than unhomogenized Labnebs. Scanning electron microscopy revealed that the largest and least uniform pores were present in traditional unhomogenized Labneh, where the protein clusters were relatively compact. Homogenization reduced the dimensions of the large pores and opened the structure of the protein clusters. Ultrafiltration of Labneh at elevated temperatures of 35° to 55°C resulted in an increase in the dimensions of the casein particles forming the protein matrix of the Labneh, evidently as the result of extended fermentation. Formation of complex casein particle chains, as observed by transmission electron microscopy, was associated with increased firmness of Labneh samples concentrated at temperatures above 45°C

Microstructure and Firmness of Processed Cheese Manufactured from Cheddar Cheese and Skim Milk Powder Cheese Base

Processed cheese (10 different types) was made from Cheddar cheese and a cheese base produced from reconstituted skim milk powder by blending and melting with commercial emulsifying salts at 9Q\u3c\u3eC. In one experiment, the cheese base was subjected 10 accelerated cheese ripening by added enzyme. The finished products had 50.1- 53.5% total solids, 18.2-19.3% protein, 47.4-49.7% fat in dry matter, and 2.7-3.0% salt in water; pH was 5.3-5.4 after three months of storage at 10 C and 30 C. The experimental cheeses were markedly firmer than the control cheeses. All processed cheeses exhibited a similar pattern of firmness whereby the samples stored at 10 C were firmer than the fresh cheeses and the cheeses stored at 30 C were firmest. Only blends containing a large proportion of a cheese base treated with added enzyme were crumbly and were not satisfactory. Electron microscopy revealed differences in the structures of the raw materials and the processed cheeses. The cheese base, to which a protease was added. had an open structure compared to a compact structure of the untreated cheese base. The microstructures of all the finished processed cheeses stored at 10 C: were similar to each other. Storage of these cheeses for 3 months at 30°C resulted in the development of irregularly shaped fat particles, but differences in their dimensions were statistically not significant

Formation and Degradation of Beta-casomorphins in Dairy Processing

Milk proteins including casein are sources of peptides with bioactivity. One of these peptides is beta-casomorphin (BCM) which belongs to a group of opioid peptides formed from b-casein variants. Beta-casomorphin 7 (BCM7) has been demonstrated to be enzymatically released from the A1 or B b-casein variant. Epidemiological evidence suggests the peptide BCM 7 is a risk factor for development of human diseases, including increased risk of type 1 diabetes and cardiovascular diseases but this has not been thoroughly substantiated by research studies. High performance liquid chromatography coupled to UV-Vis and mass spectrometry detection as well as enzyme–linked immunosorbent assay (ELISA) has been used to analyze BCMs in dairy products. BCMs have been detected in raw cow’s milk and human milk and a variety of commercial cheeses, but their presence has yet to be confirmed in commercial yoghurts. The finding that BCMs are present in cheese suggests they could also form in yoghurt, but be degraded during yoghurt processing. Whether BCMs do form in yoghurt and the amount of BCM forming or degrading at different processing steps needs further investigation and possibly will depend on the heat treatment and fermentation process used, but it remains an intriguing unknown

Rheology and Microstructure of Strained Yoghurt (Labneh) Made From Cow\u27s Milk by Three Different Methods

Labneh is the name for strained yoghurt, i.e., yoghurt made with an elevated solids content, which has originated in the Middle East. For this study , three types of Labneh were made from cow\u27 s milk: (a) Traditional Labneh was produced by straining yoghurt in a cloth bag, (b) UF Labneh was made by ultrafiltration of warm yoghurt , and , (c) UF Retentate Labneh was obtained by culturing homogenised ultrafiltration (UF) milk retentate. A 11 products were passed through a lactic curd homogen is er to smoothen the Labneh curd . Total solids contents of t he products were within the range of 21.0 to 24 . 2%, protein was 6 .8 to 8.2% and fat was 9.2 to 10.5%. Rheological properties such as consistency of traditional Labneh and UF labneh were similar and no syneresis was observed after breaking the coagulum. The coagulum of the UF Retentate labneh was very firm and its texture was crumbly . Syneresis was noticeable after the coagulum had been broken. The best sensory attributes were found with the UF Labneh followed by the traditional labneh whereas the UF Retentate Labneh appeared not to be satisfactory. Electron microscopy revealed that the microstructures of all three labnehs were similar and consisted of casein micelle chains and clusters. Minute fat particles which originated from the homogenization of milk or retentate were embedded in the casein micelle clusters. Smoothening somewhat reduced the dimensions of t he casein particle chains and clusters i n all Labnehs

Rheology and Microstructure of Strained Yoghurt (Labneh) Made From Cow\u27s Milk by Three Different Methods

Labneh is the name for strained yoghurt, i.e., yoghurt made with an elevated solids content, which has originated in the Middle East. For this study , three types of Labneh were made from cow\u27 s milk: (a) Traditional Labneh was produced by straining yoghurt in a cloth bag, (b) UF Labneh was made by ultrafiltration of warm yoghurt , and , (c) UF Retentate Labneh was obtained by culturing homogenised ultrafiltration (UF) milk retentate. A 11 products were passed through a lactic curd homogen is er to smoothen the Labneh curd . Total solids contents of t he products were within the range of 21.0 to 24 . 2%, protein was 6 .8 to 8.2% and fat was 9.2 to 10.5%. Rheological properties such as consistency of traditional Labneh and UF labneh were similar and no syneresis was observed after breaking the coagulum. The coagulum of the UF Retentate labneh was very firm and its texture was crumbly . Syneresis was noticeable after the coagulum had been broken. The best sensory attributes were found with the UF Labneh followed by the traditional labneh whereas the UF Retentate Labneh appeared not to be satisfactory. Electron microscopy revealed that the microstructures of all three labnehs were similar and consisted of casein micelle chains and clusters. Minute fat particles which originated from the homogenization of milk or retentate were embedded in the casein micelle clusters. Smoothening somewhat reduced the dimensions of t he casein particle chains and clusters i n all Labnehs

Microstructure of Set-Style Yoghurt Manufactured from Cow\u27s Milk Fortified by Various Methods

Five different batches of skim milk were prepared and fortified by the addition of skim milk powder (SMP) or sodium caseinate (Na-cn) or by concentration using a vacuum evaporator (EV), ultrafiltration (UF), or reverse osmosis (RO) to contain similar levels of protein (5.0-5.5%). Yoghurts were made by inoculating the milks with one of 3 commercial yoghurt starter cultures and by incubating the mixes at 42°C for 2.5 h. The following factors were found in this study to affect firmness of the yoghurts: (a) Lactic acid production (acidity) - Yoghurts containing 1.02% of lactic acid or more (pH 4.54 or less) were firmer than yoghurts having a lower lactic acid content and a higher pH value. (b) Casein to non-casein protein ratio - Firmer yoghurts were obtai ned at a ratio of 4.62 than at 3.20-3.4D. Microstructure of the yoghurts as examined by electron microscopy was affected by the method of fortification of the milk. SMP-fortified yoghurt had the most dense matrix composed of short micellar chains and small micellar clusters. This was the softest yoghurt. Na-co-fortified yoghurt had the most open matrix consisting of robust casein particle chains and large clusters. This was the firmest yoghurt. Appendages or spikes formed by heatdenatured B-lactoglobulin or by a complex consisting of B-lactoglobulin and K-casein were attached to casein micelles in all the yoghurts except the one fortified by the addition of Na-cn. Void spaces (cavities) around lactic acid bacteria and filaments of mucous or slimy material produced by a ropy bacterial culture and attaching the bacterial cells to the protein matrix were additional microstructural features observed in the yoghurts under study