Production of higher alcohols during indonesian tapé ketan fermentation.

A study was made of the higher alcohols (fusel oils) produced during the Indonesian tapé ketan fermentation using Amylomyces rouxii as the principal mold, alone or in combination with yeasts belonging to genera commonly found in the tapé ketan fermentation (Endomycopsis, Candida, and Hansenula). Total fusel oils increased with length of fermentation. Fusel oils detected in the product distillate included isobutanol and isoamyl and active amyl alcohols. No n-propanol was detected. Isobutanol and isoamyl alcohols were formed in the largest amounts. A. rouxii alone produced nearly the same quantity of fusel oils (total production, 275 mg/liter at 192 h) as it did in combination with Endomycopsis burtonii (total production, 292 mg/liter at 192 h).A. rouxii and Endomycopsis fibuliger produced fusel oils totaling 72 mg/liter at 32 h and 558 mg/liter at 192 h. A. rouxii in combination with Candida yeasts produced somewhat more fusel oils, ranging from 590 to 618 mg/liter at 192 h. A. rouxii in combination with Hansenula yeasts produced the least fusel oils, totaling 143 to 248 mg/liter at 192 h. During the first 36 h, production of fusel oils was higher at 30 and 35 degrees C than at 25 degrees C. At 48 h fusel oil production was slightly higher at 30 degrees C than at 35 degrees C. Beyond 48 h, production of fusel oils was higher at 25 degrees C. A. rouxii in combination with Hansenula anomala and Hansenula subpelliculosa produced considerable ethyl acetate, ranging from 145 to 199 mg/liter at 36 h and 354 to 369 mg/liter at 192 h.

Production of vitamin B-12 in tempeh, a fermented soybean food.

Several varieties of soybeans contained generally less than 1 ng of vitamin B-12 per g. It was found that use of a lactic fermentation typical of tropical conditions during the initial soaking of the soybeans did not influence the vitamin B-12 content of the resulting tempeh. Pure tempeh molds obtained from different sources did not produce vitamin B-12. It was found that the major source of vitamin B-12 in commercial tempeh purchased in Toronto, Canada, was a bacterium that accompanies the mold during fermentation. Reinoculation of the pure bacterium onto dehulled, hydrated, and sterilized soybeans resulted in the production of 148 ng of vitamin B-12 per g. The presence of the mold, along with the bacterium, did not inhibit or enhance production of vitamin B-12. Nutritionally significant amounts of vitamin B-12 were also found in the Indonesian fermented food, ontjom.

Indonesian tapé ketan fermentation.

Indonesian tapé ketan is a fermentation in which a mold, Amylomyces rouxii Calmette (Chlamydomucor oryzae Went and Prinsen Geerligs), in combination with one or more yeasts such as Endomycopsis burtonii converts steamed rice to a sweet-sour, slightly alcoholic paste. A study was made to determine the biochemical changes that occur in the substrate during fermentation. It was found that the product was ready for consumption after fermentation at 30 degrees C for 36 to 48 h. A. rouxii used about 30% of the total rice solids, resulting in a crude protein of 12% in 96 h, whereas the combination of the mold with E. burtonii reduced total solids by 50% in 192 h, causing crude protein to increase to 16.5%. Soluble solids increased from 5 to about 67% in 36 h and decreased to 12% at 192 h with A. rouxii alone, whereas soluble solids fell to about 8% at 192 h in the fermentation with both the mold and the yeast. The mold, by itself, reduced the starch content of the rice from 78 to 10% in 48 h and to less than 2% in 144 h. The mold plus yeast reduced the starch content to about 18% in 48 h; however the "starch" content did not fall below 6% even at 192 h, presumably because the yeast was producing glycogen, which was determined along with the residual starch. With both the mold and the mold plus yeast fermentations, reducing sugars increased from less than 1% to approximately 5% in 24 h and reached maximum concentration, 16 to 17%, between 36 and 48 h. A. rouxii by itself produced a maximum of about 5.6% (vol/vol) ethanol at 96 h. The highest concentration of ethanol (8%, vol/vol) was produced by the mold plus E. burtonii at 144 h. The mold by itself reduced the starting pH from 6.3 to about 4.0 in 48 h. The combination of the mold and yeast reduced the pH to 4.1 in 144 h. The mold increased total acidity to approximately 6.2 meq of H per 100 ml, and the combination of the mold and yeast increased the total acidity to 7.8 meq of H per 100 ml in 192 h. At 48 h there was practically no difference in the volatile acidity (0.20) for the combined fermentation compared with 0.26 meq of H per 100 ml for the mold fermentation. The mold and at least one species of yeast were required to develop the rich aroma and flavor of typical Indonesian tapé.