Comparative study of methods for the determination of proteolytic activity in lactic acid bacteria and selection of an autochthonous starter to manufacture Manchego cheese

The acidifying and proteolytic activity of 18 isolates of Lactococcus and Lactobacillus isolated from artisanal and industrial Manchego cheeses were studied in order to know which of them presented the best activities to be employed in the manufacture of this cheese. Of the two methods used to evaluate the proteolytic activity, Folin-Ciocalteau and o-pthaldehyde (oPA) methods, the latter gave higher values and showed a higher discriminating capacity with important differences for the values obtained for Lc. lactis subsp. lactis isolates. Of all the isolates studied, the Lactococcus lactis subp. lactis (Lc 8) showed the highest acidifying (0.79 % lactic acid) and proteolytic (2.19 mmol Gly/L) activity and could be selected as a starter culture for Manchego cheese manufacture.