Introduction: Identification of reconstituted milk is complicated because conventional heat-treatment markers reflect cumulative time-temperature load and do not always distinguish spray drying from intensive heating of liquid milk. Raman spectroscopy can register changes in protein, carbohydrate, and lipid regions without chemical sample preparation. However, physically and chemically interpretable ratiometric features that allow the spectral response of pasteurized milk to be compared with changes formed during drying and retained after reconstitution remain insufficiently developed.

Objective: To identify ratiometric features in Raman spectra that differ among raw, pasteurized, and reconstituted milk and to assess differences between samples produced from whole milk powder obtained under two drying regimes.

Materials and Methods: A single batch of milk was studied in raw form, after pasteurization at 76, 88, and 98 °C, after drying under regimes characterized by outlet-air temperatures of ≤70 and approximately 95 °C, and after reconstitution to a calculated total-solids content of 12.1%. Spectra were recorded using an M532 Raman microscope at 532 nm and analyzed from the integrated areas of bands at 1004, 1070, 1265, 1440, and 1660 cm^-1. The S₁₆₆₀/S₁₂₆₅, S₁₀₇₀/S₁₂₆₅, S₁₀₇₀/S₁₄₄₀, and S₁₀₇₀/S₁₀₀₄ ratios were calculated. Three technical measurements were performed for each sample.

Results: In the reconstituted samples, the integral area of the phenylalanine band, S₁₀₀₄, was 2.7 and 4.6 times higher than that in the raw milk. Conversely, the empirical index S₁₀₇₀/S₁₀₀₄ in the reconstituted milk decreased significantly to values of 2.17 and 2.56 (compared to 7.58 in the raw milk). The area of the S₁₄₄₀ band decreased by approximately 45 and 31%. The S₁₀₇₀/S₁₄₄₀ index increased from 0.21 in the raw milk to 0.30 and 0.48 in the reconstituted samples.

Conclusions: The model series revealed ratiometric features sensitive to the combined effects of drying, reconstitution, and heat-treatment regime. The observed values should be regarded as preliminary ranges rather than diagnostic thresholds. Validation using independent batches is required, with control of raw-milk composition, homogenization, storage, and between-day measurement variability.

Introduction: The intensification of dairy farming requires precise nutritional management, including the use of yeast-based feed additives to stabilize rumen fermentation and support the immune status of dairy cows. However, empirical evidence on the effects of different yeast components remains fragmented: live yeasts are predominantly studied in the context of rumen physiology, whereas inactivated forms are investigated primarily from the perspective of systemic immunomodulation. The absence of a unified typology that differentiates yeast products according to their mechanisms of action and conditions of efficacy precludes the formulation of evidence-based recommendations for their use.

Purpose: To systematize current scientific literature on the effects of various yeast components on the physiological and productive parameters of lactating dairy cows.

Materials and Methods: The literature search was conducted in Scopus, Web of Science, PubMed, Google Scholar, Elibrary for the period 2015–2025. From 703 initial records, 64 original articles were selected according to PRISMA-ScR guidelines.

Results: The share of publications on postbiotic forms increased from 33% (2015–2020) to 48% (2021–2025). Live yeast was shown to be effective as a rumen fermentation modulator and an adaptogen under heat stress, whereas fermentation products (postbiotics) exhibit systemic immunomodulatory and antioxidant effects, particularly important during the transition period.

Conclusions: A trend towards the use of postbiotics and personalised feeding strategies has been identified. Promising research directions include direct comparative studies of all component types, integration of ruminal and immunological outcomes, dosage standardisation, and large-scale industrial trials.