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Open access

Noel F. Sommer, Jack R. Buchanan, and Robert J. Fortlage

Abstract

Pectolytic enzymes of fungal origin (mostly Rhizopus spp.) contaminating raw apricot fruits may not be completely inactivated during thermal processing (i.e., 100°C/18 minutes). The remaining enzymes may seriously macerate fruits over a 6-to-18 month period after canning. Inactivation of crude enzymes was near exponential over a 4-log-cycle reduction of activity after heating at 121°C for up to 20 minutes. Serious overcooking of fruit at elevated temperatures discouraged further studies of heat inactivation. Laboratory and cannery tests demonstrated that a dilute spray or dip of sodium hydroxide (i.e., 1n/1 minute) at ambient temperature offered an inexpensive, simple means of inactivating fungal enzymes contaminating apricot fruits. Crucial to success was accurate maintenance of solution concentration and contact times. For adequate penetration of solutions, the fruit skins over fungal lesions required breaking. Jet sprays broke the skin over the Rhizopus softrot lesions if they contacted all fruit surfaces.

Open access

Jack R. Buchanan, Noel F. Sommer, and Robert J. Fortlage

Abstract

Aflatoxin production by Aspergillus flavus growing on potato-dextrose agar, cooked rice medium, and raw pistachio nuts, was suppressed in 2 ways. First, CO suppressed growth of the fungus if O2 was low. Second, CO suppressed aflatoxin production, evidently by interfering with aflatoxin metabolism, even if the atmosphere permitted nearly normal fungal growth. Fungal growth was equal or better in 2% O2 than in air (20.8% O2). Addition of 10% CO slowed growth materially only if O2 was low, but aflatoxin accumulation was suppressed by CO only slightly more in low O2 atmospheres. After growth for 32 days at 20°C in cooked rice medium or raw pistachios in an atmosphere containing 2% O2 + 10% CO, aflatoxin was <2% of the production in an atmosphere containing 2% O2 or air without CO.

Open access

J. R. Buchanan, N. F. Sommer, R. J. Fortlage, E. C. Maxie, F. G. Mitchell, and D. P.H. Hsieh

Abstract

Concentrations of patulin in blue mold lesions caused by Penicillium expansum Lk. ex Thom in pears and stone fruits were similar to those reported for apples. Of fruits tested, only the plum was a poor substrate for accumulation of the mycotoxin. The total patulin within disease lesions increased as the lesions enlarged. However, the concentration of patulin varied considerably, with the largest lesions usually yielding the lowest concentrations. Little or no patulin permeated healthy tissue surrounding the disease lesions unless fruits were overripe or had senescent breakdown.