No abstract

Micellar casein (MC) dispersions were studied at a constant protein concentration of 5 wt % in high NaCl environment. The micellar edifices were characterized as to their morphology, size, and content of proteins in the supernatant after ultracentrifugation. Additionally, changes in secondary structures of the protein upon salt increase were followed by Fourier Transform Infrared Spectroscopy (FTIR). For the first time, the estimations of secondary structural elements (irregular, ß-sheet, α-helix and turn) from Amide III assignments were correlated with results from Amide I. Casein micelles dispersions in water were characterized by Transmission Electron Microscopy (TEM) by a spherical shape and a size between 100 and 200 nm. A salt increase resulted to a destabilization of the micelle and the formation of mini-micelles more or less aggregated. The size of the new edifice was almost similar to the native micelle. These TEM observations were confirmed by a constant casein micelle hydrodynamic diameter determined by Dynamic Light Scattering (DLS) and ranging between 150 and 180 nm. Upon salt increase, FTIR revealed an increase in irregular structures and a concurrent decrease in ß-sheet structures. Secondary structural elements percentages were almost similar from Amide I and Amide III. The use of these multiscale techniques led to a better understanding of the micellar edifice under high salt environment. Around 3% NaCl addition, a good correlation was observed between destabilization of the micellar edifice, modifications of the caseins secondary structure and repartition of caseins between supernatant and pellet after ultracentrifugation.

Rehydration of native micellar casein and native whey isolate protein powders was followed in different ionic environments. Solutions of NaCl and CaCl2 in the concentration range of 0 to 12% (wt%) were used as rehydration media. The rehydration profiles obtained were interpreted in terms of wetting, swelling, and dispersion stages by using a turbidity method. Two behaviors were observed depending on the salt concentration. For native micellar casein powder, a significant change was observed between 3 and 6% NaCl and between 0.75 and 1.5% CaCl2. The first behavior (low salt concentration) presents a typical rehydration profile: quick wetting, swelling, and long dispersion stage. The dispersion stage of the second behavior (high salt concentration) was significantly shortened, indicating a strong modification of the protein backbone. The rehydration of whey protein powder was less influenced by salts. At low salt concentrations, a typical profile for whey powders was observed: wetting with lump formation and no swelling followed by a quick dispersion. At high CaCl2 concentrations, no turbidity stabilization was observed, indicating a possible protein unfolding and denaturation. Additionally, the changes in secondary structures of the 2 proteins upon salt increase were followed by Fourier transform infrared spectroscopy and confirmed the different profiles observed.

Nutraceutical products have gained prominence nowadays owing to their plethora of suggested positive health attributes. Several types of foods have likewise been indicated to provide a wide variety of functional health properties. Especially, functional foods with probiotic properties, such as fermented milks containing lactic acid bacteria and yeast, have generated considerable regard, sourdough bread has received recent attention as wheat fermentation could improve essential mineral bioavailability and provide additional health and nutritional benefits including the provision of probioticmicrobes. Sourdough fermentation is also associated with anti‐fungal and anti‐bacterial properties that can improve bread shelf life and quality including the provision of attractive organoleptic characteristics. In addition, this review succinctly highlights the fermentation of wheat from Pakistani perspective, antinutritional factors, and their pros and cons, allergic compounds in wheat and their degradation by fermentation and various other methods to improve nutritional value and quality that have appeared in the recent research. Practical applications The field of sourdough microbiology and technology is currently limited by the number of comprehensive review articles with study on novel microorganisms known to degrade gluten, with much research focus on phytic acid and gliadin degradation. This review article will broaden the knowledge of food scientist who are working in the field of sourdough bread. This review article also discusses the microbiota responsible for nutraceutical bread production in baking industry. Sourdough technology is mushrooming in many areas of the world due to its myriad health and quality benefits.

No abstract