The effect of adding freeze or heat-shocked Lactobacillus delbrueckii subsp.
helveticus DSMZ 20082 + commercial starter (Lactococcus lactis subsp. cremoris,
Lactococcus lactis subsp. lactis, Leuconostoc mesenteroides subsp. cremoris and
Lactococcus lactis subsp. diacetilactis) to cheese milk (cow's and buffalo's milk 1:1
standardized to 3.5% fat) to accelerate Gouda cheese ripening and improve the quality
compared with controls (cheese treated with commercial starter alone and cheese treated
with commercial starter + viable cells of Lb. helveticus). Resultant cheese was then kept in
the ripening room at 10-12ºC and 85-95% relative humidity for 3 months. Cheese samples
were analyzed chemically, microbiologically, rheologically and organoleptically when
fresh and after 30, 60 and 90 days of ripening. The obtained results indicated that the
ripening indices (SٍN, SN/TN, soluble tyrosine & tryptophan and T.V.F.A contents); the
proteolytic & lipolytic bacterial counts and sensory evaluation scores increased with the
increase of ripening period. The cheese treated with freeze-shocked Lb. helveticus had the
highest values of these parameters followed by cheese treated with heat-shocked Lb.
helveticus compared with other treatments in all stages of ripening. Cheese treated with
freeze or heat-shocked Lb. helveticus had more desirable texture along ripening and there
was a reduction of 33% in the ripening period compared to other treatments.
The patterns of free fatty acids and electrophoretic patterns in control cheese treated
with commercial starter alone and cheese treated with freeze-shocked Lb. helveticus at 90
days showed higher levels of volatile fatty acids and higher number of bands of protein
respectively in cheese treated with freeze-shocked Lb. helveticus than that of control
cheese.