Analysis of the nature of the composition substances of sour-milk dessert with plant-based fillers

The nature and interaction of the constituent substances that make up the sour-milk dessert with plant-based fillers have been studied by the method of IR spectroscopy. This method is used to study the diverse nature of substances. The spectral range applied was in the range of 500–4,000 s -1. It was found that the intensity of functional groups absorption in the range of 2,500–3,500 s-1 is due to the valence vibrations of NH-, CH and S-H-groups, indicating the presence of free organic acids, aromatic substances. In addition, in the spectra of sour-milk dessert with plant-based fillers, an absorption intensity in the range of 1,470–1,335 s-1 is observed, which indicates the presence of soluble pectin. Proteins characteristics in the samples are observed at absorption in the range of 3,300–3,500 cm -1, which is due to the valence vibrations of the N-H bond in the -NH2 groups. The use of fruits in the form of a freeze-dried powder together with milk protein concentrate in the technology of sour-milk desserts helps reduce the content of free moisture, hence a stable structure. Sour-milk dessert with plant-based fillers is a system consisting of particles of different dispersion, which will affect its physical and chemical properties. In particular, there is a slight coarsening of whey proteins and redistribution between particles in the range of 1–10 nm and 1–100 nm. The use of plant-based fillers in the form of a freeze-dried powder in the technology of sour-milk desserts would not only improve its physical and chemical properties but also could make it possible to enrich the product with minerals. The mineral composition of the sour-milk dessert is marked by the calcium content (122 mg/100 g), potassium (97 mg/100 g), phosphorus (82 mg/100 g), sodium (50 mg/100 g), and sulfur, iron.

Principles of lactose crystallization and rheology of milk protein concentrate

Milk protein concentrate (MPC) is a commercial designation for dairy ingredients with higher protein and lower lactose content than conventional skim milk powder. Lactose in its amorphous form is found in several spray-dried dairy powders. Amorphous lactose is thermodynamically unstable and can mobilize and crystallize over time under adequate temperature and moisture content. Moisture sorption from the air precedes crystallization, enhancing MPC cohesiveness and caking. This increased humidity results in poor rehydration and dispersibility, lower yield during drying, operation problems, difficulties in handling and storage. Moreover, lactose crystallization in MPC can cause Maillard browning reaction and fat oxidation. To avoid this problem, it is necessary to pre-crystallize lactose as alpha-lactose monohydrate, which is non-hygroscopic, before spray drying. Such a procedure is essential in preventing deterioration of MPC resulting from lactose crystallization or chemical reactions. Additionally, the control of this step is important to obtain specified and reproducible powder, in terms of size and crystallization level. There are various reports on the rheology of milk-based products; however, there is a lack of investigation on concentrated systems. Consequently, the objective of the present work is to review basic concepts of lactose crystallization and rheology of milk protein concentrate.

Bioactive Peptides from Liquid Milk Protein Concentrate by Sequential Tryptic and Microbial Hydrolysis

Recently, bioactive peptides as a health-promoting agent have come to the forefront of health research; however, industrial production is limited, possibly due to the lack of the required technological knowledge. The objective of the investigation was to prepare bioactive peptides with hypoallergenic properties from liquid milk protein concentrate (LMPC), through sequential enzymatic and microbial hydrolysis. LMPC was produced from ultra-heat-treated (UHT) skimmed cow’s milk using a nanofiltration membrane. The effect of the concentration of trypsin (0.008–0.032 g·L−1) on the hydrolysis of LMPC was studied. Subsequently, the hydrolysis of tryptic-hydrolyzed LMPC (LMPC-T) with lactic acid bacteria was performed, and the effect of glucose in microbial hydrolysis was studied. Aquaphotomic analysis of the hydrolysis of LMPC was performed using the spectral range of 1300–1600 nm (near-infrared spectra). Changes in antioxidant capacity, anti-angiotensin-converting enzyme activity, and antibacterial activity against Bacillus cereus, Staphylococcus aureus and Listeria monocytogenes were noted after the sequential tryptic and microbial hydrolysis of LMPC. Allergenicity in LMPC was reduced, due to sequential hydrolysis with 0.016 g·L−1 of trypsin and lacteal acid bacteria. According to the aquaphotomic analysis result, there was a dissociation of hydrogen bonds in compounds during the initial period of fermentation and, subsequently, the formation of compounds with hydrogen bonds. The formation of compounds with a hydrogen bond was more noticeable when microbial hydrolysis was performed with glucose. This may support the belief that the results of the present investigation will be useful to scale up the process in the food and biopharmaceutical industries.