Influencing cocoa flavour using Pichia kluyveri and Kluyveromyces marxianus in a defined mixed starter culture for cocoa fermentation

TY - JOUR

T1 - Influencing cocoa flavour using Pichia kluyveri and Kluyveromyces marxianus in a defined mixed starter culture for cocoa fermentation

AU - Crafack, Michael

AU - Mikkelsen, Morten Baastrup

AU - Saerens, Sofie

AU - Knudsen, Morten

AU - Blennow, Andreas

AU - Lowor, Samuel

AU - Takrama, Jemmy

AU - Swiegers, Jan H.

AU - Petersen, Gert B.

AU - Heimdal, Hanne

AU - Nielsen, Dennis Sandris

N1 - Conference code: 23

PY - 2013/10/1

Y1 - 2013/10/1

N2 - The potential impact of aromatic and pectinolytic yeasts on cocoa flavour was investigated using two defined mixed starter cultures encompassing strains of Pichia kluyveri and Kluyveromyces marxianus for inoculating cocoa beans in small scale tray fermentations. Samples for microbial and metabolite analysis were collected at 12-24hour intervals during 120h of fermentation. Yeast isolates were grouped by (GTG)5-based rep-PCR fingerprinting and identified by sequencing of the D1/D2 region of the 26S rRNA gene and the actin gene. Pulsed Field Gel Electrophoresis (PFGE) was conducted on isolates belonging to the species P. kluyveri and K. marxianus to verify strain level identity with the inoculated strains. Furthermore, Denaturing Gradient Gel Electrophoresis (DGGE) was performed to follow yeast and bacterial dynamics over time including the presence of the bacterial inoculum consisting of Lactobacillus fermentum and Acetobacter pasteurianus. Yeast cell counts peaked after 12h of fermentation with the predominant species being identified as Hanseniaspora opuntiae and Hanseniaspora thailandica. P. kluyveri and K. marxianus were found to compose 9.3% and 13.5% of the yeast population, respectively, after 12h of fermentation whilst PFGE showed that ~88% of all P. kluyveri isolates and 100% of all K. marxianus isolates were identical to the inoculated strains. Despite never being the dominant yeast species at any stage of fermentation, the un-conched chocolates produced from the two inoculated fermentations were judged by sensory analysis to differ in flavour profile compared to the spontaneously fermented control. This could indicate that yeasts have a greater impact on the sensory qualities of cocoa than previously assumed.

AB - The potential impact of aromatic and pectinolytic yeasts on cocoa flavour was investigated using two defined mixed starter cultures encompassing strains of Pichia kluyveri and Kluyveromyces marxianus for inoculating cocoa beans in small scale tray fermentations. Samples for microbial and metabolite analysis were collected at 12-24hour intervals during 120h of fermentation. Yeast isolates were grouped by (GTG)5-based rep-PCR fingerprinting and identified by sequencing of the D1/D2 region of the 26S rRNA gene and the actin gene. Pulsed Field Gel Electrophoresis (PFGE) was conducted on isolates belonging to the species P. kluyveri and K. marxianus to verify strain level identity with the inoculated strains. Furthermore, Denaturing Gradient Gel Electrophoresis (DGGE) was performed to follow yeast and bacterial dynamics over time including the presence of the bacterial inoculum consisting of Lactobacillus fermentum and Acetobacter pasteurianus. Yeast cell counts peaked after 12h of fermentation with the predominant species being identified as Hanseniaspora opuntiae and Hanseniaspora thailandica. P. kluyveri and K. marxianus were found to compose 9.3% and 13.5% of the yeast population, respectively, after 12h of fermentation whilst PFGE showed that ~88% of all P. kluyveri isolates and 100% of all K. marxianus isolates were identical to the inoculated strains. Despite never being the dominant yeast species at any stage of fermentation, the un-conched chocolates produced from the two inoculated fermentations were judged by sensory analysis to differ in flavour profile compared to the spontaneously fermented control. This could indicate that yeasts have a greater impact on the sensory qualities of cocoa than previously assumed.

U2 - 10.1016/j.ijfoodmicro.2013.06.024

DO - 10.1016/j.ijfoodmicro.2013.06.024

M3 - Journal article

SN - 0168-1605

VL - 167

SP - 103

EP - 116

JO - International Journal of Food Microbiology

JF - International Journal of Food Microbiology

IS - 1

T2 - International ICFMH Symposium FoodMicro 2012

Y2 - 3 September 2012 through 7 September 2012

ER -