Abstract
Starter culture-initiated cocoa fermentation processes can be applied to improve the quality of cured cocoa beans. However, an accurate monitoring of the microbial strains inoculated in fresh cocoa pulp-bean mass to assess their contribution to the cocoa bean curing process is still lacking. In the present study, eight different cocoa fermentation processes were carried out with Trinitario cocoa in vessels in Costa Rica to assess the contribution of two candidate yeast starter culture strains, namely Saccharomyces cerevisiae IMDO 050523 and Pichia kudriavzevii IMDO 020508, inoculated in combination with Limosilactobacillus fermentum IMDO 0611222 and Acetobacter pasteurianus IMDO 0506386. A multiphasic approach, consisting of culture-dependent selective plating and incubation, rRNA-PCR-DGGE community profiling of agar plate washes, and culture-independent high-throughput amplicon sequencing, combined with a metabolite target analysis of non-volatile and volatile organic compounds (VOCs), was performed on samples from the fermentation and/or drying steps. The different starter culture mixtures applied effectively steered the cocoa fermentation processes performed. Moreover, the use of an amplicon sequence variant (ASV) approach, aligning these ASVs to the whole-genome sequences of the inoculated strains, allowed the monitoring of these inoculated strains and their differentiation from very closely related variants naturally present in the background or spontaneous fermentation processes. Further, traits such as malolactic fermentation during the fermentation step and acetoin and tetramethylpyrazine formation during the drying step could be unraveled. Finally, the yeast strains inoculated influenced the substrate consumption and metabolite production during all starter culture-initiated fermentation processes. This had an impact on the VOC profiles of the cured cocoa beans. Whereas the P. kudriavzevii strain produced a wide range of VOCs in the cocoa pulp, the S. cerevisiae strain mostly influenced the VOC composition of the cured cocoa beans.
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Claims 8
Claim · model-written summary
Starter culture mixtures steered cocoa fermentation.
- Taxon
- cocoa
Theobroma cacaoe0 - Treatment
- starter culture mixturese0
- Outcome
- cocoa fermentation processese0
- Direction
- steerede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The different starter culture mixtures applied effectively steered the cocoa fermentation processes performed.”
Claim · model-written summary
ASV alignment distinguished inoculated strains from close background variants.
- Outcome
- monitoring of these inoculated strains and their differentiatione0
- Comparator
- very closely related variantse0
Not reportedTaxon
Verbatim
e0“an amplicon sequence variant (ASV) approach, aligning these ASVs to the whole-genome sequences of the inoculated strains, allowed the monitoring of these inoculated strains and their differentiation from very closely related variants naturally present in the background or spontaneous fermentation processes”
Claim · model-written summary
Malolactic fermentation was resolved during fermentation.
Not reportedTaxon
Verbatim
e0“traits such as malolactic fermentation during the fermentation step and acetoin and tetramethylpyrazine formation during the drying step could be unraveled.”
Claim · model-written summary
Acetoin and tetramethylpyrazine formation was resolved during drying.
Not reportedTaxon
Verbatim
e0“acetoin and tetramethylpyrazine formation during the drying step could be unraveled.”
Claim · model-written summary
Inoculated yeast strains influenced substrate consumption and metabolite production.
Not reportedTaxonComparatorDirection
Verbatim
e0“the yeast strains inoculated influenced the substrate consumption and metabolite production during all starter culture-initiated fermentation processes.”
Claim · model-written summary
Inoculated yeasts affected VOC profiles of cured cocoa beans.
- Taxon
- cocoaTheobroma cacaoe0
- Outcome
- VOC profiles of the cured cocoa beanse0
Not reportedTreatmentComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This had an impact on the VOC profiles of the cured cocoa beans.”
Claim · model-written summary
P. kudriavzevii produced a wide range of VOCs in cocoa pulp.
- Taxon
- P. kudriavzevii
Pichia kudriavzeviie0 - Organ / stage
- cocoa pulpe0
- Outcome
- wide range of VOCse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the P. kudriavzevii strain produced a wide range of VOCs in the cocoa pulp”
Claim · model-written summary
S. cerevisiae mostly influenced VOC composition of cured cocoa beans.
- Taxon
- cocoaTheobroma cacaoe0
- Treatment
- S. cerevisiae straine0
- Outcome
- VOC composition of the cured cocoa beanse0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the S. cerevisiae strain mostly influenced the VOC composition of the cured cocoa beans.”