Inhibition of Aspergillus parasiticus speare by Cladosporum fulvum cooke in peanuts

Date

10-1995

Abstract

This study was evaluated the inhibitory activity of Cladosporium fulvum against Aspergillus parasiticus in peanut kernels using different concentrations of crude extract and culture broth. This was under different pH levels, temperatures and varying moisture contents. It also determined the effect of the metabolite on the viability of stored peanut kernels and it's toxicity on test chicks.

C. fulvum was mass-produced on Malt Extract Broth where elaboration of the metabolite was indicated by formation of the characteristic reddish color which is specific for the organism.

The inhibitory activity of the crude extract and culture broth against A. parasiticus was evaluated through the agar cup technique. The crude extract at 100 µg inhibited growth of A. parasiticus at the pigmented zone which was up to 24 mm around the agar cup. Similar growth characteristics were observed with C. fulvum culture broth at 100% concentration. For both crude extract and culture broth, formation of a yellow-greenish zone around the agar cup was evident. Microscopic examination of these zones recealed scanty yellow-greenish fungal growth. There were also less and smaller spores and shortening, thinning and distortion of hyphae. Of these two forms, the crude extract exhibited greater inhibitory activity.

Complete inhibition of A. parasiticus was possible at 100 to 50% culture broth in peanut kernels with 5.2 to 5.4% moisture content up to 6 months. Normal and luxuriant growth was evident in peanut kernels with 8.50 to 8.72% moisture content even at 100% culture broth.

Restricted and abnormal growth of A. parasiticus was evident in peanut kernels with 6.23% moisture content at 80 to 30 µg. Similar growth characteristics were observed in peanut kernels with 6.1 to 6.77% moisture content at 100 to 50% culture broth. Growth was characterized by localized, tiny fungal growths with yellow-greenish mycelia and spores indicating effective inhibition.

The pH (4.0, 5.0, 6.0 and 7.0) of the culture broth exerted minimal effect on inhibition of A. parasiticus. Good growth was evident at all pH levels. However, mold counts were relatively higher at pH 5.0 and lower at pH 4.0.

The effect of temperature on inhibition of A. parasiticus was also minimal. Abundant growth was evident at 29oC (room temperature) and 32oC at all concentrations of the crude extract and culture broth at relatively high moisture content. Growth inhibition was possible at both temperatures only at low moisture content.

Essentially, factors such as temperature, concentration and pH play minor roles in inhibition of A. parasiticus. Low moisture content is the most critical factor affecting inhibition of A. parasiticus in peanut kernels . If moisture is low, A. parasiticus is inhibited even without treatment. Treatment however is useful if moisture content us higher than 5.4%.

A 100% germination test was possible for peanut kernels treated with the culture broth after one week and 85 to 86% after 3 months of storage at room temperature.

The metabolite is non-toxic to test chicks. Normal growth and a 100% survival was evident in test chicks after continuous ad libitum feeding for 7 days.

Document Type

Dissertation

Degree

Doctor of Philosophy in Food Science

College

Graduate School (GS)

Adviser/Committee Chair

Reynaldo C. Mabesa

Committee Member

Linda B. Mabesa, Nimfa P. Roxas, Ernesto V. Carpio

Language

English

LC Subject

Peanuts, Cladosporium fulvum, Aspergillus

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

LG 996 1995 F61 D44

Notes

Doctor of Philosophy (Food Science)

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