Formation kinetics of hydroxymethylfurfural and brown coloured compounds in goat milk during heating

The formation of hydroxymethylfurfural, nonenzymatic brown coloured compounds and free sulphydryl groups in goat milk was studied during heating at 75–95 °C. Analysis of kinetic data suggested that formation of hydroxymethylfurfural and nonenzymatic brown coloured compounds followed zero order reaction kinetics, while formation of free sulphydryl groups during heating varied depending on heating time. A good linear correlation (r = 0.839) was found between brown coloured compounds and hydroxymethylfurfural content in milk samples during heating. Activation energies (E_a) for the formation of hydroxymethylfurfural and nonenzymatic brown coloured compounds were 96.31 and 69.79 kJ/mol, respectively.     

Characterisation of aroma‐active compounds,chemical and sensory properties of acid‐coagulated cheese: Circassian cheese

The objectives of this study were to determine basic composition, aroma and sensory characteristics of Circassian cheese. Seven Circassian cheeses were provided by local producers. Aroma compounds were extracted by using solid‐phase microextraction procedure and determined by gas chromatography‐olfactometry system. Water‐soluble, trichloroacetic acid‐soluble and phosphotungstic acid‐soluble nitrogen fractions ranged between 2.30–29.35%, 2.48–9.96% and 3.33–6.26%, respectively. Diacetyl, butyric acid, 2‐acetyl‐1‐pyrroline, 1‐octen‐3‐one and methional were identified at high intensities in cheeses. In addition, ‘cooked’, ‘whey’, ‘creamy’ and ‘fermented’ were defined as characteristic flavour terms for Circassian cheeses.     

EFFECTS OF FUNCTIONAL DAIRY BASED PROTEINS ON NONFAT YOGURT QUALITY

Production of nonfat yogurt demands a careful control of quality parameters. It is common to use skim milk powder (SMP) to increase the total solid content of nonfat yogurt, but some functional dairy-based proteins, such as casein/caseinates and whey proteins, may improve the quality of nonfat yogurt.
The objectives of this study were to use whey protein isolate (WPI), sodium caseinate (NaCn) and yogurt texture improver (TI) in nonfat yogurt manufacture as an alternative for SMP, and to compare their potential influences on the physical, chemical and microbial properties of nonfat yogurts over a 12-day storage. All dry ingredients were added at 1% (w/v) concentration to yogurt milk. Yogurts differed from each other with different hardness values. Acetaldehyde contents of yogurts were in the range of 35–43 ppm. The acetaldehyde content of all yogurt types decreased during storage. The control yogurt had the most tyrosine content, and the WPI-fortified yogurt had the least. Using different dry dairy ingredients did not affect the numbers of starter cultures. In addition, no significant differences were observed among yogurt types regarding their mineral composition.

PRACTICAL APPLICATIONS

Functional dry dairy ingredients can be used to increase the total solid content of nonfat yogurt instead of using skim milk powder (SMP) or evaporation. Their high protein content, water-binding capacity, texture improvement properties and health benefits make these proteins suited for use in nonfat yogurts. This study compares the possible effects of using whey protein isolate (WPI), sodium caseinate (NaCn) and yogurt texture improver (TI) as an alternative for SMP on the physical, chemical and microbial properties of nonfat yogurts. It was found that substitution of SMP for WPI, NaCn and TI at the level of 1% affected the physical, chemical and microbial properties of nonfat yogurt.