CHANGES IN THE CHEMICAL-COMPOSITION OF ORANGE JUICE DURING GROWTH OF SACCHAROMYCES-CEREVISIAE AND GLUCONOBACTER-OXYDANS

The fate of several compounds, including saccharides, has been followed in citrus juice during fermentation by Saccharomyces cerevisiae and Gluconobacter oxydans. Concentrated juice reconstituted at 11.8-degrees Brix was sterilized by filtration to give a clear serum and allowed to ferment with the micro-organisms which were isolated from the same juice. Glucose, fructose and sucrose were rapidly metabolized by the yeasts. The fall in sugar concentration was associated with a rise in ethanol and meso-inositol (MI) which reached a plateau, while epi-inositol (EP) remained unaffected. Production of oligosaccharides (OS) began after 24 h incubation at 25-degrees-C and were generated simultaneously during the next 24 h. OS and almost all the saccharides were eliminated from the solution by 56 h. The bacterium slowly utilized sucrose, glucose and 2/3 of the Ml; however, fructose was poorly metabolized. Very large amounts of OS with increasing molecular size were produced over time. Results suggest that the yeast and the bacterium may have symbiotic interactions during an uninoculated, natural fermentation of reconstituted orange juice. This study also showed that OS generated by micro-organisms are significantly different from those produced by acid hydrolysis of sucrose.