18D-3


Penicillium digitatum growth response as affected by solute and acid type at selected water activities and pHs

L. C. CORONADO1, E. Palou2, and A. Lopez-Malo1. (1) Departamento de Ingeniería Química y Alimentos, Universidad de las Américas-Puebla, Sta. Catarina Mártir, Cholula, Puebla, 72820, Mexico, (2) Center for Engineering Education, Univ. de las Americas, Puebla, Cholula, Puebla, 72820, Mexico

Penicillium digitatum is a common deteriorative organism of several fruits and is resistant to acidic environments and relatively low water activities. Due to the variety of environments in which this mold causes spoilage, solute and acid type may affect its response. Mold response in laboratory media formulated at aw 0.99, 0.95, or 0.90, pH 5, 4, or 3 when using sodium chloride, sucrose or glucose to adjust aw, in combination with acetic, citric, phosphoric or tartaric acid to reduced pH was evaluated. Solid media formulated with every factor combination was inoculated with 103 spores/ml, and incubated at 27º C up to 30 days. Periodically during incubation, mold colony diameter was measured, determining if growth or inhibition (growth delay) occurred. An ANOVA demonstrated that individual variables as well as their interactions significantly (p<0.05) affected lag time. P. digitatum grew in 83 of the 108 evaluated cases. When growth was observed, lag time increased as aw and pH decreased. The combination of aw 0.90 and pH 3.0 inhibit mold growth independently of the type of solute or acid used in the media. No growth after 30 days of incubation was observed when sodium chloride was used to adjust aw in combination with pH 3. Combinations of low aw and pH caused mold inhibition in more cases when sodium chloride and acetic or phosphoric acid were used. Acetic acid significantly (p<0.05) inhibit mold growth in more cases than the other evaluated acids, growth was observed in only 11 of the 27 evaluated combinations. Acid and solute type exhibited an important effect on P. digitatum response demonstrating their importance when used to adjust pH and aw.

Session 18D, Food Microbiology: General
2:00 PM - 5:30 PM, Sunday PM Room Hall I-2

2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana