Optimizacija fermentacije na trdnih gojiščih za proizvodnjo nadomestka kakava

Bojanec, Valentina (author), Čadež, Neža (mentor), Paš, Maja (comentor)

Pridelava kakava se sooča z resnimi okoljskimi in socialno-ekonomskimi izzivi, kar vodi v manjšo razpoložljivost in višje cene kakava. V zadnjih letih se zato pojavlja vse več podjetij in zagonskih pobud, ki razvijajo trajnostne nadomestke kakava in čokolade. V nalogi smo preučevali možnost uporabe mešane združbe mikroorganizmov za predelavo rastlinskih surovin v nadomestek kakava s fermentacijo na trdnih gojiščih. Fermentacijo smo zasnovali po vzoru naravne fermentacije kakavovih zrn, ter jo preizkusili na različnih oblikah grozdnih pešk in na sončničnih semenih. Bioproces je potekal v dveh zaporednih fazah: anaerobni s kvasovkami vrste Saccharomyces cerevisiae in/ ali Hanseniaspora opuntiae in mlečnokislinskimi bakterijami vrste Lactiplantibacillus plantarum, ter aerobni z ocetnokislinskimi bakterijami vrste Acetobacter pasteurianus. Potek populacijske dinamike in kinetike fermentacije smo spremljali z določanjem števila kolonijskih enot, vrednosti pH ter porabo prostih sladkorjev in nastajanjem metabolitov. Izvedli smo fermentacije različnih substratov in postopke postopoma izboljševali. Za najbolj obetavni substrat se je izkazala kombinacija celih grozdnih pešk in grozdnih tropin. Med anaerobno fazo se je koncentracija kvasovk povečala z 106 na 108–109 CFU/g, pri čemer je mikrobna združba proizvedla do 27 g/L etanola, medtem ko so bakterije A. pasteurianus v aerobni fazi dosegle koncentracijo do 1010 CFU/g. Vrednost pH se je v anaerobni fazi znižala, v aerobni pa ponovno zvišala. Enostavne sladkorje so mikroorganizmi porabili že v prvih petih dneh. Po koncu fermentacije smo substrat posušili in spražili, ter nato fino zmleli v krogličnem mlinu. Končni prašek je imel gladko teksturo. Vmešali smo ga v belo čokoladno osnovo. Senzorična ocena je pokazala prijetne sadno-vinske note brez neprijetnih priokusov. Čeprav aroma še ni popolnoma značilna za kakav, izdelek kaže potencial kot trajnostni lokalni nadomestek kakava. Za doseganje izrazitejše čokoladne arome je potrebna nadaljnja optimizacija procesa.

• Language: Slovenian
• Keywords: fermentacija na trdnih substratih, nadomestki kakava, grozdne peške, kvasovke, mlečnokislinske bakterije, ocetnokislinske bakterije
• Work type: Master's thesis/paper
• Organization: BF - Biotechnical Faculty
• Year: 2026
• PID: 20.500.12556/RUL-190982
• Publication date in RUL: 09.11.2026

Secondary language

• Language: English
• Title: Solid-state fermentation optimization for production of cocoa alternative

Abstract

Cocoa production faces serious environmental and socio-economic challenges, which may lead to reduced availability and higher prices of cocoa. In recent years, an increasing number of companies and start-ups have begun developing sustainable alternatives to cocoa and chocolate. In this thesis, we investigated the potential of solid state fermentation for converting plant-based raw materials into a cocoa substitute. The fermentation process was modelled after the natural fermentation of cocoa beans and tested on various forms of grape and sunflower seeds. The process consisted of two phases: an anaerobic phase with yeast species Saccharomyces cerevisiae and/ or Hanseniaspora opuntiae and lactic acid bacteria species Lactiplantibacillus plantarum, followed by an aerobic phase with the acetic acid bacteria species Acetobacter pasteurianus. The population dynamics of the fermentation were monitored by determining colony-forming units, pH values, consumption of free sugars, and the formation of metabolites. We performed fermentations of various substrates and gradually optimized the procedures. The most promising substrate proved to be a combination of whole grape seeds and grape pomace. During the anaerobic phase, the yeast concentration increased from 106 to 108–109 CFU/g, with the microbial community producing up to 27 g/L of ethanol, while A. pasteurianus bacteria reached concentrations of up to 1010 CFU/g in the aerobic phase. The pH value decreased during the anaerobic phase and increased during the aerobic phase. The microorganisms consumed the simple sugars within the first five days. After fermentation, the substrate was dried and roasted, then finely ground in a ball mill. The final powder had a smooth texture. It was incorporated into a white chocolate base. Sensory evaluation revealed pleasant fruity- wine notes without unpleasant aftertastes. Although the aroma is not yet fully characteristic of cocoa, the product shows potential as a sustainable local cocoa substitute. Further process optimization is needed to achieve a more pronounced chocolate aroma.

• Keywords: solid state fermentation, cocoa alternatives, grape seeds, yeast, lactic acid bacteria, acetic acid bacteria