The aim was to identify to what extent proteins were utilized during the fermentation of bacteria-free tempe prepared with acidified soybean cotyledons and Rhizopus oligosporus NRRL 2710 at 30 degrees C. Dry matter declined continuously during the fermentation to 980 g/(kg of initial dry cotyledons) at 28 h, 910 g at 46 h (when the tempe was judged mature), and 835 g at 72 h. The decrease in dry matter was due mainly to reduction in crude lipid, amounting to 65 g/(kg of initial dry cotyledons) at 46 h and 135 g/(kg of initial dry cotyledons) at 72 h and representing approximately 70% and 80%, respectively, of the total dry matter loss. Protein oxidation (estimated from ammonia production) was 5 g at 28 h,10 g at 46 h, and 20 g/(kg of initial dry cotyledons) at 72 h. The total amount of soy protein hydrolyzed, including that incorporated into mold biomass, was estimated to be 80 g/(kg of initial dry cotyledons) at 28 h incubation, 95 g at 46 h, and 100 g at 72 h. The hydrolyzed protein at 46 h represented 25% of the initial protein. Of this hydrolyzed protein, it is suggested that approximately 65% remained in the tempe as amino acids and peptides, 25% was assimilated into mold biomass, and 10% was oxidized.

Aims: To investigate the effects of temperature, pH, water activity (a w ) and CO 2 concentration on the growth of Rhizopus oligosporus NRRL 2710. Methods and Results: Hyphal extension rates from mycelial and spore inocula were measured on media with different a w ($ 1AE0, 0AE98 and 0AE96) and pH (3AE5, 5AE5 and 7AE5) incubated at 30, 37 or 42°C in atmospheres containing 0AE03, 12AE5 or 25% (v/v) CO 2 . The effects of environmental conditions on hyphal extension rate were modelled using surface response methodology. The rate of hyphal extension was very sensitive to pH, exhibiting a pronounced optimum at pH 5AE5-5AE8. The hyphal extension rate was less sensitive to temperature, a w or CO 2 , exhibiting maximum rates at 42°C, a w $ 1AE0 and 0AE03% (v/v) CO 2 . Conclusions: The fastest hyphal extension rate (1AE7 mm h )1 ) was predicted to occur at 42°C, pH 5AE85, a w $ 1AE0 and 0AE03% CO 2 .Significance and Impact of the Study: The present work is the first to model the simultaneous effects of temperature, pH, a w and CO 2 concentration on mould growth. The information relates to tempe fermentation and to possible control of the microflora in Tanzanian cassava heap fermentations.

No abstract

No abstract

The hyphal extension rate of Rhizopus oligosporus NRRL 2710 was slowed in the presence of 0·42 and 0·84 mmol NH3 l−1 and inhibited by 1·3 mmol l−1. Sporulation was prevented at NH3 concentrations of 0·42 mmol l−1 andabove. There was no evidence of toxicity due to NH+4 at concentrations up to 300 mmol l−1.Independent of the concentrations of NH3 or NH+4, the lower the pH value, in therange 6·0–9·0, the higher was the rate of hyphal extension. It is suggested that accumulationof toxic levels of NH3 could be responsible for the cessation of mould growth in tempe.