Evaluation of Freeze-Dried Kefir Coculture as Starter in Feta-Type Cheese Production

Abstract

The use of freeze-dried kefir coculture as a starter in the production of feta-type cheese was investigated. Maturation of the produced cheese at 4°C was monitored for up to 70 days, and the effects of the starter culture, the salting method, and the ripening process on quality characteristics were studied. The use of kefir coculture as a starter led to increased lactic acid concentrations and decreased pH values in the final product associated with significantly higher conversion rates compared to salted rennet cheese. Determination of bacterial diversity at the end of the ripening process in salted kefir and rennet cheeses by denaturing gradient gel electrophoresis technology, based on both DNA and RNA analyses, suggested a potential species-specific inhibition of members of the genera Staphylococcus and Psychrobacter by kefir coculture. The main active microbial associations in salted kefir cheese appeared to be members of the genera Pseudomonas and Lactococcus, while in salted rennet cheese, Oxalobacteraceae, Janthinobacterium, Psychrobacter, and Pseudomonas species were noted. The effect of the starter culture on the production of aroma-related compounds responsible for cheese flavor was also studied by the solid-phase microextraction-gas chromatography-mass spectrometry technique. Kefir coculture also appeared to extend the shelf life of unsalted cheese. Spoilage of kefir cheese was observed on the 9th and 20th days of preservation at 10 and 5°C, respectively, while spoilage in the corresponding rennet cheese was detected on the 7th and 16th days. Microbial counts during preservation of both types of unsalted cheese increased steadily and reached similar levels, with the exception of staphylococci, which were significantly lower in unsalted kefir cheese. All types of cheese produced with kefir as a starter were approved and accepted by the panel during the preliminary sensory evaluation compared to commercial feta-type cheese.

Effect of Probiotic-Fermented Milk Administration onGastrointestinal Survival of <i>Lactobacillus casei</i> ATCC 393 and Modulation of Intestinal Microbial Flora

“…Hence, it is not unreasonable to suggest the development of a microbial association, due to L. casei ATCC 393 cells, leading to repression of facultative pathogens, although pathogenesis has not been considered for all strains of the above microbial species. Suppression of staphylococci growth has been described in various food products by mixed LAB cultures [Dimitrellou et al, 2009;Kourkoutas et al, 2006b], while reduction of pathogenic bacteria counts in feces [de Waard et al, 2002;O'Mahony et al, 2001] and intestines of rats [de Waard et al, 2002;Liong et al, 2006;Montesi et al, 2005], due to the action of LAB and bifidobacteria has been previously reported. Further research using deliberately spiked animals with pathogens will give more insight into the role of L. casei ATCC 393 as endogenous protecting shield.…”

Study of proteolysis, lipolysis, and volatile compounds of a Camembert-type cheese manufactured using a freeze-dried Tibetan kefir co-culture during ripening

“…The microflora of kefir grains is remarkably stable, retaining activity for years if preserved and incubated under appropriate cultural and physiological conditions (1). Successful results have been achieved in studies where kefir was used as a starter culture for production of white pickled cheese (2), hard-type cheese (3), and Feta-type cheese (4).…”

Characterization and seasonal variation of the quality of virgin olive oil of the Throumbolia and Koroneiki varieties from southern Greece

“…Kovat's retention indexes were determined from the injection of a standard mixture containing the homologous series of normal alkanes (C 8 -C 22 ) in pure hexane under exactly the same experimental conditions as described above. Quantification of volatile compounds was carried out as described recently (Mallouchos et al, 2003;Kourkoutas et al, 2006) with some modifications. Specifically, methyl octanoate (Sigma-Aldrich, Poole, UK) diluted in pure hexane (Sigma-Aldrich) was used as an internal standard (IS) at various concentrations (0.88, 8.75, 87.5, and 875 µg/kg).…”