Effect of addition of different dairy ingredients on the quality of yogurt

Description

Research Hypothesis: Yogurt flavor depends on both starter cultures and dairy base composition. Different ingredients alter flavor precursors (amino acids, fatty acids), directing microbial metabolism to produce distinct key flavor compounds and sensory profiles. Data & Methods: Flavor differences were characterized using sensory evaluation, E-nose, GC×GC-O-MS (for OAVs and concentrations of 19 key odorants), and HPLC (for amino and organic acids). Correlation analyses linked chemical and sensory data. Key Findings: Whey protein (WP) yogurt performed best, with the highest levels of key volatiles (e.g., acetoin, diacetyl), organic acids, and sweet amino acids (alanine, lysine), resulting in superior creamy/fresh aroma and balanced taste. Core flavor drivers were acetoin (OAV=76), acetic acid (OAV=181), diacetyl (OAV=30), and 2-nonanone (OAV=52). Milky aroma correlated with acetoin, fresh with styrene, and fishy odor with hexanoic/butyric acids. Interpretation & Application: High OAV compounds drive sensory perception. For optimal flavor, use whey protein. To correct fishy off-notes, trace and reduce precursors like caproic/butyric acid by adjusting ingredients or process.

Steps to reproduce

1. Sample Preparation Yogurts were prepared by blending milk with dairy ingredients (Table 1), homogenizing (150 MPa), pasteurizing, cooling to 42 °C, inoculating with Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus, and fermenting at 42 °C for 4.5–5 h (final acidity 75 °T). 2. Sensory Analysis A trained panel (n=12) performed Quantitative Descriptive Analysis, scoring seven attributes (milky, sweet, fermented, creamy, fishy, grassy, sour) on a 0‑5 scale using reference standards. 3. Instrumental Analysis 3.1. E‑nose: PEN3 system; sample 20 g, 40 °C equilibration, 400 mL/min flow. Data processed with Winmuster (PCA). 3.2. Volatiles (DHS‑GC×GC‑O‑MS): Sampling: 20 g yogurt + 5 g NaCl + internal standard; DHS at 60 °C, N₂ purge 180 mL/min for 50 min, trapped on Tenax‑TA. GC×GC‑O‑MS: Agilent 8890A/5977B; columns DB‑WAX (1D) and DB‑17ms (2D); oven 40 °C (4 min) to 230 °C at 4 °C/min; MS scan *m/z* 33‑350. Olfactometry port for aroma description. Identification/Quantitation: NIST 17 library, retention index (C8‑C25 alkanes), standards; 19 key compounds quantified via internal calibration. 3.3. Taste Compounds (HPLC): Free Amino Acids: Agilent 1260, Zorbax Eclipse‑AAA column; pre‑column OPA/FMOC derivatization; external calibration with 15 standards. Organic Acids: Agilent 1260, Waters T3 column; extraction with 0.5% H₃PO₄; external calibration with 9 standards. 4. Data Processing Odor Activity Value (OAV) = concentration / odor threshold in water. ANOVA (SPSS 26), graphing/correlation heatmaps (Origin 2024). 5. Reagents & Materials Dairy ingredients: fermented thin cream, cheese powder, cream cheese, whey protein, etc. Chemical standards from Sigma‑Aldrich, Macklin, TCI. Columns: DB‑WAX, DB‑17ms, Zorbax Eclipse‑AAA, Waters T3, Tenax‑TA tubes.

Institutions

• Beijing Technology and Business University

  Beijing, Beijing

Categories

Licence