Alcohol and Acetaldehyde in African Fermented Milk Mursik—A Possible Etiologic Factor for High Incidence of Esophageal Cancer in Western Kenya

Abstract

Background: Esophageal cancer is unusually frequent in Western Kenya, despite the low prevalence of classical risk factors such as heavy drinking and tobacco smoking. Among Kenyans consumption of fermented milk is an old tradition. Our hypothesis is that alcohol and acetaldehyde are produced during the fermentation process and that their carcinogenic potential contributes to the high incidence of esophageal cancer.Methods: Eight samples of mursik milk starter cultures were collected from different Kalenjin families in the Rift Valley province, Western Kenya. A protocol provided by the families was used for milk fermentation. Ethanol and acetaldehyde levels were measured by gas chromatography. The microbial flora in starter cultures was identified by 16S and 18S sequencing.Results: 7/8 starter cultures produced mutagenic (>100 mmol/L) levels of acetaldehyde and 4/8 starter cultures produced more than 1,000 mmol/L of acetaldehyde. The highest alcohol levels (mean 79.4 mmol/L) were detected in the four fermented milks with highest acetaldehyde production. The mean number of microbial species in the starter cultures was 5 (range 2-8). Yeasts were identified in all starter cultures (mean 1.5 species/milk) but their proportion of the total microbial count varied markedly (mean 35%, range 7%-90%). A combination of yeast and lactobacilli, especially Candida krusei with Lactobacillus kefiri, with the exclusion of other species, seemed to correlate with higher acetaldehyde and ethanol levels.Conclusions: Significant levels of ethanol and acetaldehyde were produced during mursik fermentation. Impact: When ingested several times daily the repeated exposure to carcinogenic levels of acetaldehyde may contribute to esophageal carcinogenesis. Cancer Epidemiol Biomarkers Prev; 22(1); 69-75. Ó2012 AACR.

Spontaneously fermented kenyan milk products: A review of the current state and future perspectives

“…Whereas Nieminen et al (2013) recorded L. kefiri as the dominant LAB; Digo (2015) did not record it. The differences could be ascribed to the broad variation of Mursik due to household differences in preparation of Mursik and/or due to geographical differences.…”

“…Nieminen et al (2013) analyzed Mursik samples that were fermented using small batches of Mursik collected from Kenya. The total microorganisms at 48 and 72 h of fermentation were 10.42±0.21 and 9.54±0.43 log 10 cfu/mL, respectively.…”

“…Eight Lactobacillus species were identified and the Lactobacillus kefiri was more frequent in the samples (6 out of 8 samples) with a mean of 37% of the colonies. (Nieminen et al, 2013). Muigei et al (2013) attempted to identify exopolysaccharide-producing LAB in Mursik obtained from Nakuru County, Kenya.…”

“…The differences could be ascribed to the broad variation of Mursik due to household differences in preparation of Mursik and/or due to geographical differences. Moreover, Nieminen et al (2013) used a back-sloping method to produce Mursik using small batches of Mursik that had stayed at room temperature for 4 weeks. These differences could also explain why Digo (2015) detected coliforms that were not identified by Nieminen et al (2013).…”

“…Fermented foods and the microorganisms that contribute to the fermentation process have also been associated with many beneficial effects on human health and food preservation, however they are underexploited. Although there have been studies characterizing the microorganisms in some of the Kenyan spontaneously fermented products (Lore et al, 2005;Mathara et al, 2004;Nieminen et al, 2013;Nyambane et al, 2014), there has been no technology in Kenya that has been developed to modernize the production of the traditional fermented products using starter cultures under controlled conditions or exploiting their probiotic and antimicrobial potential (FAO, 2010;Reid et al, 2014). This is partly because most studies intended to characterize traditional fermentations employs the classical microbiological culturing techniques, which are inadequate in identifying and characterizing microbial consortia.…”