EFFECT OF ALLYLISOTHIOCYANATE AND RELATED SUBSTANCES ON THE THERMAL RESISTANCE OF ASPERGILLUS NIGER, SACCHAROMYCES ELLIPSOIDEUS, AND BACILLUS THERMO ACIDURANS^a

Abstract

I n a previous report we reviewed the use of mustard seed and allylisothiocyanate (mustard oil) as preservatives for fruit juices ( 3 ) , and preliminary data on the preservation of fresh cider and grape juice by these substances was reported, It was indicated that allylisothiocyanate in concentrations of approximately 20 p. p. m., exerted a favorable preservative action on fresh cider.The present investigation was carried out to ascertain the effect of allylisothiocyanate, oil of garlic, and oil of onion on the thermal resistance of Aspe+gillus niger, Xaccharomyces ellipsoideus, and Bacillus themnoacidurans. These organisms were examples of spoilage microorganisms that might be encountered in acid foods. EXPERIMENTAL PROCEDURE MicroorganismsThe representative test organisms selected were Aspergillus niger and Saccharomycea ellipsoideus, taken from stock cultures in this laboratory, and Bacillus thermoaciclurans, strain number 8038 (Bacillus coagulam) from the American Type Culture Collection. SubstratesCitric acid-dibasic sodium phosphate buffer solutions for pH 4.0 and 7.0 were prepared according t o McIlvaine ( 4 ) . Freshly pressed apple juice was filtered and held in the frozen state in glass containers prior to use. The juice employed had a pH value of 3.9 and a soluble solids content of 13.8%. Pasteurized Concord. grape juice was prepared in the laboratory. It had a pH value of 3.8 and a soluble solids content of 16.5%. A given lot of washed, trimmed tomatoes cut into quarters, were placed in a steamjacketed kettle and heated t o boiling. Then the hot pulp was passed through a cyclone finisher and the juice was then filled at 87.7"C.(190°F.) into No. 10 (603 x 700) unlined cans which were processed in boiling water. Preparation of Spore and Yeast Cell SuspensionsThe Aspergillus niger spore crops were grown on slants of dextrose agar (Difco) and apple juice agar (prepared by adding 2% ag&r to apple juice) for 12 days at room temperature [21a to 24"C.(70° to 75"F.)]. The spores were washed from the agar slants with sterile physiological saline and collected in a sterile flask. The spore 811s-pension was then filtered through a sterile cheese cloth cotton filter pad and the filtrate placed in 50-ml. centrifuge tubes and centrifuged for 15 minutes a t 3,000 r.p.m. to concentrate the spores. The spores were washed from the centrifuge tube with 5 ml. of saline and placed in a sterile flask containing glass beads. The spore concentration was Contribution No. 808, Massachusetts Agricultural Experiment Station. Present address,

Antifungal vapour‐phase activity of allyl‐isothiocyanate against Penicillium expansum on pears

“…, 1993). Similar activity was observed with AITC in studies with Penicillium glaucum and Staphylococcus aureus (Virtanen, 1962); and Aspergillus niger and Saccharomyces ellipsoideus (Kosker et al. , 1951).…”

The role of myrosinase in the development of toxicity toward Nematospora in mustard seed

“…3 confirm that sinigrin hydrolysis products, resulting from myrosinase action, were indeed volatile. It should be noted that Kosker et al (1951) reported a decrease in thermal resistance of Saccharomyces in the presence of 10 ppm allyl isothiocyanate. Increased sensitivity was also evident when Nematospora were present during hydrolysis at elevated temperatures (Fig.…”

HEAT SENSITIZATION OF BACILLUS SUBTILIS SPORES BY SELECTED SPICES

“…The specific mechanism(s) responsible for the apparent sensitization of spores by spices is unclear, although all spices used in this study have been reported to inhibit microbial growth (Pruthi 1980;Shelef 1983). In addition, garlic, cinnamon and cloves have been reported to affect various stages of spore development (Mantis et al 1979;Shelef et al 1984;Al-Khayat and Blank 1985). Based on the MIC values of the spices: 0.13,0.25, 1.50, 4.0 and > 5.0%, w/v for sage, clove, cinnamon, garlic and black pepper respectively, it would appear that carry-over concentrations during serial dilution and plating would be insufficient to prevent spore outgrowth and replication.…”