Microbiota dynamics and diversity at different stages of industrial processing of cocoa beans into cocoa powder.
We sampled a cocoa powder production line to investigate the impact of processing on the microbial community size and diversity at different stages. Classical microbiological methods were combined with 16S rRNA gene PCR-denaturing gradient gel electrophoresis, coupled with clone library construction, to analyze the samples. Aerobic thermoresistant spores (ThrS) (100°C; 10 min) were also isolated and characterized (identity, genetic diversity, and spore heat resistance), in view of their relevance to the quality of downstream heat-treated cocoa-flavored drinks. In the nibs (broken, shelled cocoa beans), average levels of total aerobic microorganisms (TAM) (4.4 to 5.6 log CFU/g) and aerobic total spores (TS) (80°C; 10 min; 4.3 to 5.5 log CFU/g) were significantly reduced (P < 0.05) as a result of alkalizing, while fungi (4.2 to 4.4 log CFU/g) and Enterobacteriaceae (1.7 to 2.8 log CFU/g) were inactivated to levels below the detection limit, remaining undetectable throughout processing. Roasting further decreased the levels of TAM and TS, but they increased slightly during subsequent processing. Molecular characterization of bacterial communities based on enriched cocoa samples revealed a predominance of members of the Bacillaceae, Pseudomonadaceae, and Enterococcaceae. Eleven species of ThrS were found, but Bacillus licheniformis and the Bacillus subtilis complex were prominent and revealed great genetic heterogeneity. We concluded that the microbiota of cocoa powder resulted from microorganisms that could have been initially present in the nibs, as well as microorganisms that originated during processing. B. subtilis complex members, particularly B. subtilis subsp. subtilis, formed the most heat-resistant spores. Their occurrence in cocoa powder needs to be considered to ensure the stability of derived products, such as ultrahigh-temperature-treated chocolate drinks.
Laboratory of Food Microbiology, Wageningen University, Wageningen, The Netherlands.
Lídia J R
LJ
Lima
Vera
V
van der Velpen
Judith
J
Wolkers-Rooijackers
Henri J
HJ
Kamphuis
Marcel H
MH
Zwietering
M J Rob
MJ
Nout
D001420:Bacteria, Aerobic / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification; D044822:Biodiversity; D058448:Biota; D002099:Cacao / Q000382:microbiology*; D016000:Cluster Analysis; D015169:Colony Count, Microbial; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D058645:Denaturing Gradient Gel Electrophoresis; D005511:Food Handling; D007218:Industrial Microbiology; D008969:Molecular Sequence Data; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA
D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D012336:RNA, Ribosomal, 16S