Hlapljivi organski spojevi u mlijeku dobivenom prirodnom fermentacijom i fermentacijom s pomoću pojedinačnih ili mješovitih kultura kvasaca i mliječno-kiselih bakterija

Abstract

The volatile organic compounds present in 18 Zimbabwean naturally fermented milk (amasi) samples and those produced by various yeasts, lactic acid bacteria (LAB) and yeast/ LAB combinations were determined using headspace gas chromatography. The yeast strains used were: Candida kefyr 23, C. lipolytica 57, Saccharomyces cerevisiae 71, C. lusitaniae 68, C. tropicalis 78, C. lusitaniae 63, C. colliculosa 41, S. dairenensis 32, and Dekkera bruxellensis 43, and were coded Y1 to Y9, respectively. The LAB strains used were Lactococcus lactis subsp. lactis Lc39, L. lactis subsp. lactis Lc261, Lactobacillus paracasei Lb11, and L. lactis subsp. lactis biovar. diacetylactis C1, and were coded B1 to B4, respectively. Some of the volatile organic compounds found in amasi were acetaldehyde, ethanol, acetone, 2-methyl propanal, 2-methyl-1-propanol and 3-methyl-1-butanol. However, the levels of volatile organic compounds in the naturally fermented milk (NFM) samples varied from one sample to another, with acetaldehyde ranging from 0.1–18.4 ppm, 3-methyl butanal from <0.1–0.47 ppm and ethanol from 39.3–656 ppm. The LAB/C. kefyr 23 (B/Y1) co-cultures produced significantly (p<0.05) higher levels of acetaldehyde and ethanol than the levels found in the NFM. The acetaldehyde levels in the B/Y1 samples ranged from 26.7–87.7 ppm, with L. lactis subsp. lactis biovar. diacetylactis C1 (B4) producing the highest level of acetaldehyde in combination with C. kefyr 23 (Y1). Using principal component analysis (PCA), most of the NFM samples were grouped together with single and co-cultures of Lc261, Lb11 and the non-lactose fermenting yeasts, mainly because of the low levels of ethanol and similar levels of 3-methyl butanal. Chromatograms of amasi showed prominent peak of methyl aldehydes and their alcohols including 3-methyl-butanal and 3-methyl-butanol, suggesting that these compounds are important attributes of Zimbabwean naturally fermented milk.Hlapljivi organski proizvodi, u 18 uzoraka prirodno fermentiranog mlijeka iz Zimbabvea (amasi) i mlijeka dobivenog fermentacijom s pomoću kvasaca, mliječno-kiselih bakterija (LAB) i kombinacijom kvasaca i mliječno-kiselih bakterija određeni su plinskom kromatografijom na čvrstoj fazi. Upotrijebljeni su ovi sojevi kvasaca: Candida kefyr 23, C. lipolytica 57, Saccharomyces cerevisiae 71, C. lusitaniae 68, C. tropicalis 78, C. lusitaniae 63, C. colliculosa 41, S. dairenensis 32 i Dekkera bruxellensis 43, te su označeni s Y1 do Y9. Od LAB korišteni su sojevi Lactococcus lactis subsp. lactis Lc39, L. lactis subsp. lactis Lc261, Lactobacillus paracasei Lb11 i L. lactis subsp. lactis biovar. diacetylactis C1, označeni s B1 do B4. Acetaldehid, etanol, aceton, 2-metilpropanal, 2-metil-1-propanol i 3-metil-1-butanol su neki hlapljivi organskih spojevi pronađeni u prirodno fermentiranom mlijeku amasi. Količina hlapljivih organskih spojeva u prirodno fermentiranom mlijeku (naturally fermented milk – NFM) razlikovala se od uzorka do uzorka, te je iznosila 0,1-18,4 ppm acetaldehida, <0,1-0,47 ppm 3-metilbutanala i 39,3-656 ppm etanola. Upotrebom kulture LAB/C. kefyr 23 (B/Y1) proizvedena je kudikamo veća (p<0,05) količina acetaldehida i etanola nego u NFM. Količina acetaldehida u uzorcima B/Y1 iznosila je 26,7-87,7 ppm, a najviše acetaldehida dobiveno je fermentacijom s pomoću L. lactis subsp. lactis biovar. diacetylactis C1 (B4) u kombinaciji s C. kefyr 23 (Y1). Metodom glavnih komponenata (principal component analysis – PCA) svrstana je većina NFM uzoraka s pojedinačnim i mješovitim kulturama Lc261, Lb11 i kvascima koji ne fermentiraju laktozu, prema malim količinama etanola i sličnom udjelu 3-metilbutanala. Kromatogram prirodno fermentiranog mlijeka amasi pokazuje visok pik metilaldehida i njihovih alkohola, uključujući 3-metilbutanal i 3-metilbutanol, čime je dokazano da su ti spojevi značajni za mlijeko amasi