a1 Departamento de Producción y Tecnología de Alimentos, CIT-INIA, Apartado 8111, Madrid 28080, España
The influence of lactic starter inoculation on La Serena cheese characteristics was investigated in duplicate experiments, each consisting of a vat inoculated with 1% Lactococcus lactis subsp. lactis skim milk culture and a control vat without lactic starter. Lc. lactis inoculation achieved a significant pH decrease in the interior and on the surface of cheese, which ranged from 0·09 to 0·25 units throughout ripening. Breakdown of αs1- and β-casein and formation of soluble N fractions were retarded by Lc. lactis inoculation. Levels of αs1-casein, β-casein and pH 4·6-soluble N after 60 d were respectively 30·4, 34·9 and 28·8% in cheese made with starter and 18·4, 23·0 and 34·2% in control cheese. More acidic conditions in the interior of cheese made with starter resulted in a reduction of Enterobacteriaceae, coliform and staphylococci counts, which after 60 d were respectively 2·55, 2·40 and 0·29 log units lower than in control cheese. The firmer texture obtained throughout maturation for cheese made with starter was attributed to retarded proteolysis and lower pH value. Cheese flavour quality and intensity were significantly impaired by Lc. lactis inoculation.
(Received September 04 1990)
(Accepted February 24 1991)