Decontamination of Mesquite Pod Flour Naturally Contaminated with Bacillus cereus and Formation of Furan by Ionizing Irradiation†

Abstract

Mesquite pod flour produced from nitrogen-fixing trees of the Prosopis species has a unique aroma and flavor that is preferred by some consumers. Due to the presence of wildlife, grazing domestic animals, and insects, the pods have a high potential of being contaminated with human pathogenic bacteria, such as Bacillus cereus. Nonthermal processing technologies are helpful to reduce the population of microorganisms in the flour because heating deteriorates the characteristic flavor. A study was conducted to investigate the efficacy of ionizing radiation in decontaminating two types of mesquite pod flours (Prosopis alba and Prosopis pallida) naturally contaminated with B. cereus and the effects of irradiation on the formation of furan, a possible human carcinogen. Results showed that the populations of B. cereus were 3.8 and 5.4 log CFU/g in nonirradiated P. alba and P. pallida flours, respectively, and populations of microflora, mesophilic spores, B. cereus, and B. cereus spores decreased with increasing radiation doses. At 6 kGy, the populations fell below 1 log CFU/g. Irradiation at 6 kGy had no significant effect on the fructose, glucose, or sucrose content of the flour. Nonirradiated P. alba and P. pallida flours contained 13.0 and 3.1 ng/g of furan, respectively. Furan levels increased with irradiation doses at rates of 2.3 and 2.4 ng/g/kGy in the two flours. The level of 3-methylbutanal was reduced or not affected by irradiation, while the hexanal level was increased. Our results suggested that irradiation was effective in decontaminating contaminated mesquite flour. The significance of furan formation and possible changes in flavor due to irradiation may need to be further examined.