Isolation of a Caffeine-Resistant Mutant of Aspergillus parasiticus

A caffeine-resistant mutant of Aspergillus parasiticus NRRL 2999 was isolated and subsequently designated strain BCR1. The mutant strain grew in the presence of > 8 mg/mL caffeine, while growth of the parent strain was delayed by 1 mg/mL and inhibited by 2 mg/mL. Strain BCR1 produced abundant amounts of aflatoxin only when cultured in media containing caffeine. Residual caffeine analyses indicated that caffeine-resistance in BCR1 was not due to the metabolic elimination of caffeine.     

Stability of Glutamine and Pyroglutamic Acid under Model System Conditions: Influence of Physical and Technological Factors

The stability of glutamine and pyroglutamic acid as regards pH, temperature and oxygen was studied during storage and two thermal processings, the residual products and those which appeared being determined. Contrary to glutamic acid, the two derivatives are labile below pH 2 and above pH 13 and alteration occurs much faster. Temperature increase promotes this phenomenon. Glutamic and pyroglutamic acids convert reversibly into one another, more or less quickly and completely according to the conditions. Glutamine changes during heating in two steps, first into glutamic acid, then into pyroglutamic acid if the pH values are not extreme. The influence of pH conditions on the direction and the rate of the reaction are indicated.     

Partial Characterization of the Action of An A. niger Lipase on Butteroil Emulsions

A commercially available lipase (A. niger, APF-12) was employed to hydrolyze an emulsified butteroil substrate. HPLC analyses of the reaction products indicated that short chain fatty acid residues (e.g., butyric acid) were preferably hydrolyzed at pH 5 whereas the overall rate of hydrolysis for all major fatty acids showed a pH optimum between 6 and 7. This indicated the possibility of directing the selectivity of lipolysis in butteroil to enhance production of short-chain fatty acids associated with flavor development. The optimal temperature was ca. 35°C. Different cations also affected rate of hydrolysis.     

PHYSICOCHEMICAL PROPERTIES OF FOUR TOMATO CULTIVARS GROWN IN NIGERIA

The physicochemical characteristics of tomato fruits from three commercial cultivars available in the local market were compared with a Wild cultivar. The results showed that the Ibadan‐Local and Wild cultivars had a higher fruit yield than Ife‐1 and Roma‐VF cultivars. The Wild cultivar has a high skin and seed content. The shape of the fruits varied from spherical to pear‐like. Physicochemical properties such as specific gravity, pH, titratable acidity, ash and refractive index did not vary significantly while total solids, longitudinal (stem→blossom end) and cross‐sectional diameters (transverse diameter), vitamin C and reducing sugars were significantly different (P > 0.05) among the cultivars investigated. The results showed that the Wild cultivar has attributes (i.e., physicochemical characteristics) comparable to commercial cultivars to recommend it to breeders for cultivation.