Influence of Air Limitation and Histidine Addition on Citrinin Content and Color of Thai Glutinous Rice, Korkor 6( RD 6 ), Red Yeast Rice

Abstract

A strain of Monascus purpureus CMU001 was used to prepare red yeast rice from Thai glutinous rice, Korkor 6 (RD 6). Different amounts of histidine (156, 312, 625 and 1250 mg in 100 g of rice grains) were added under aerobic and air limitation (air-lock) conditions in solid fermentation. Determinations of the limit of detection (LOD) and the limit of quantitation (LOQ) for citrinin analysis by HPLC using methanol as a solvent were carried out. The LOD and LOQ for the determination of citrinin were found to be 9.775 and 24.462 mg/L (or 0.010 and 0.024 mg/g of dried red yeast rice), respectively. Citrinin content was determined in order to compare the methods used for preparation of red yeast rice. It was found that the lowest citrinin content was found to be 0.04 mg/g using air-lock conditions with 625 mg histidine addition. Production efficiency was determined by using the ratio of monacolin K to citrinin content. The highest production efficiency was found to be under the conditions with 625 mg of histidine addition and air limitation (AN3-AL). Products were also tested for the color properties by measuring the lightness (L*) and the redness (a*) values. The highly efficiently prepared red yeast rice, AN3-AL, had a significantly different L* from AN3 (normal conditions with 625 mg histidine addition) but did not have a significantly different a* from AN3 and AN-AL (air-lock conditions with no addition of histidine).