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Proceeding of the 4 rd International Symposium“NEW RESEARCH IN BIOTECHNOLOGY” USAMV Bucharest, Romania, 2011THE INFLUENCE OF RIPENING TEMPERATURE ON DIVERSITY OFNON-STARTER LACTIC BACTERIA IN SEMI-HARD CHEESESKey words: NSLAB, cheese, ripening, Lactobacillus spp.INGA CIPROVICA 1 , ALLA MIKELSONEThe role of non-starter lactic bacteria (NSLAB) in determination of cheese quality is stillunclear. The only way how to ensure quality of cheese is corrections in technological process. Theaim of the study was to evaluate impact of the selected ripening temperature on the growth rate ofNSLAB in Latvian semi-hard Holandes and Krievijas cheeses.The samples of unripened semi-hard cheeses have been analysed. Cheeses were producedat two cheese factories and ripened at laboratories of LUA for 60 days at 6 and 12 °C. Both ripeningregimes help understand better the influence of microflora on the quality of cheese, including theformation of sensory properties.The following analyses are performed in the study: pH, water activity (a w ), CFU ofLactobacillus spp., identification of Lactobacillus species and isolation of DNA for confirmation ofisolated Lactobacillus species. The obtained sequences are analysed at Staden Package 1.6.0 releaseand compared to sequences available in the BLAST (www.ncbi.nlm.nih.gov.)In order to control the rate of cheese ripening and the growth dynamics of mesophilicNSLAB, some researchers have suggested decreasing of ripening temperature. Decreasing ofripening temperature slows down the growth rate of mesophilic NSLAB, but it is impossible toliberate cheese from their presence. The differences are observed in qualitative composition of cheesemicroflora. L.curvatus dominated during the rest of the ripening time at 6 °C and L.plantarum 1 wasdetected at 12°C in cheese samples. DNA fragment sequencing of most frequently identifiedL.plantarum 1 and L.curvatus revealed that nucleotide sequence of L.curvatus of ripened cheese at6°C for 60 days conforms with the strain L.paracesei subsp. paracasei JCM8133; in cheese ripenedat 12 °C for 60 days - L.paracasei MH55. In their turn, the isolated L.plantarum 1 from cheesesamples ripened at 12 °C for 60 days conform to L.plantarum DSPV 354T.This study reveals that the concentration of NSLAB differs between cheeses ripened at 6 °C(5.26-6.90 log CFU g -1 ) and 12 °C (5.26-7.62 log CFU g -1 ) at least by 1 log. Higher concentrationswere found in cheeses ripened at 12 °C. These findings should be taking account, because thetemperature at ripening is subordinated to the rate of biochemical processes in manufacture of aparticular cheese variety. Any change has a significant impact on the whole complex of sensoryproperties of cheese.1. INTRODUCTIONRaw milk is a natural growth medium for microorganisms. Compositionand quality of milk microflora are determined not only by hygiene observation inthe places of milk production, rapidity of milk cooling and temperature, but also bymicroflora in the air of dairy environment, on the surface of equipments and1 Latvia University of Agriculture Faculty of Food Technology2 Liela street, Jelgava, LV 3001, LATVIA, phone/fax +371 63022829, E-mail: Inga.Cipovica@llu.lv226
Proceeding of the 4 rd International Symposium“NEW RESEARCH IN BIOTECHNOLOGY” USAMV Bucharest, Romania, 2011premises. An integral part of milk microflora is non-starter lactic acid bacteria.Pasteurization regime selected in cheese manufacturing is able to destroy essentialmicroflora, enzymes and pathogens in milk. It should be noted that inactivationlevel of microorganisms depends on the count of microorganisms, growth phaseand other factors. Bactofugation, microfiltration, and application of food additives,cannot significantly decrease the proportion of Lactobacillus spp. and Leuconostocspp. in milk. Defects caused by non-starter lactic acid bacteria are found in all dairyproducts, but the most problematic they are in cheeses.Early blowing caused by non-starter lactic acid bacteria is often mixed upwith coliform bacteria. Non-starter lactic acid bacteria, mostly heterofermentative,produce diacetyl and acetoin, and high amounts of carbon dioxide. Carbon dioxideforms many small holes in cheese, and sometimes a significant gas pressure resultsin a sponge-like cheese texture. Identical defect is caused by coliform bacteria.This defect occurs during the beginning of cheese ripening while there is lactose init. Technological methods to fight coliform bacteria differ as well. If milk isproduced according to hygienic requirements, food additives are not necessary fordecreasing of activity of coliform bacteria. Over consumption of sodiumnitrate/sodium nitrite is not beneficial for consumers. Cheesemakers are confusedabout the defect, its origin and possible solution. Enzymes produced byLactobacillus spp. are able to hydrolyze casein forming bitter peptides, whichinfluence flavour characteristics of cheese.The non-starter lactic acid bacteria could not be evaluatedunambiguously. Individual strains of species are used for acceleration ofcheese ripening, stimulation of hydrolysis of proteins and enhancement ofconcentration of free amino acids contributing to flavour and aroma of awell ripened cheese. It should be noted that the role of non-starter lactic acidbacteria in determination of the cheese quality is still unclear. The aim ofthe study was to evaluate impact of the selected ripening temperature on thegrowth rate of NSLAB in Latvian semi-hard Holandes and Krievijascheeses.2.MATERIALS AND METHODSThe samples (n=18) of unripened semi-hard Krievijas and Holandescheeses have been chosen for analysis. Cheeses were produced at two cheesefactories in Latvia and ripened at laboratories of Latvia University of Agriculture.Cheeses are manufactured according to the technical requirements of the enterpriseor the Branch Standards: LPCS 10: 2001 and LPCS 11: 2001. The technology of227
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