Effect of specialized combined strains on reconstituted milk reduced-fat cheese
The reduced-fat cheese using reconstituted milk powder (CRMP) has the problems of texture and flavor because of heating and drying treatments of milk. The application of an exopolysaccharide (EPS)-producing strain, as well as an adjunct strain in CRMP was investigated to address these quality issues. Volatiles of these cheeses were determined by solid phase microextraction-gas chromatography-mass spectrometry and texture by the textural profile analysis. The EPS-producing strain could hold moisture and result in cheese with higher yield compared to the non EPS-producing strain. Meanwhile, the cheese made with the EPS-producing Streptococcus thermophilus TM11 had a lower hardness, springiness, chewiness, gumminess, resilience and a higher adhesiveness and cohesiveness than the cheese made with non EPS-producing S. thermophilus SP1.1. These changes were attributed to the differences of protein matrix according to observation of scanning electron microscopy. On the other hand, results of the main flavor compounds in CRMP indicated that combination of the EPS-producing S. thermophilus TM11 and an adjunct Lactococcus lactis ssp. lactis could provide CRMP with novel and proper flavor properties while improving the textural characteristics.
Key words: Reconstituted milk, reduced-fat cheese, Streptococcus thermophilus, texture, flavor.