M. L. Fields

The flat sour bacteria.

Publisher Summary In 1897, Prescott and Underwood published a paper, which described the souring of canned sweet corn. These authors distinguished between two types of souring, one which resulted in swelling of the can and the other which did not. It is possible that some of the souring without swelling of the can may have been the flat sour spoilage, as it is known today. They stated that one part of a particular canners single-day production was shipped to the northern part of the United States, whereas another portion was shipped to the southern part of the United States. The canned corn sent to the northern part was perfect at the end of a year, while the corn shipped to the South became sour. The original batch of canned corn could have had flat sour spores present, which caused spoilage when the corn was stored at a warm temperature. The canning industry has described spoilage of low-acid foods by B.stearothermophilus as flat sour spoilage and spoilage of tomato juice by B.cougulans as aciduric flat sour spoilage. These bacteria produce acid, but no gas, from carbohydrates and produce the typical flat sour spoilage in canned foods. This chapter discusses about the distribution of spores of flat sour bacteria through soil and water, milk, sugar and starch, various other ingredients, wheat and wheat products. Next, this chapter looks at the resistance of spores to lethal agents. This is followed by a discussion on sources of contamination in canning plant. This chapter ends with the discussion on control of flat sour bacteria and its biology.

Food quality as determined by metabolic by-products of microorganisms.

Publisher Summary Food quality is largely the sum of the characteristics, which register favorably or adversely on an individuals senses. These characteristics include freshness, flavor, odor, texture, tenderness, consistency, color, size and shape, degree of ripeness, and presence or absence of defects. Nutritive value, chemical residues, and disease-producing organisms are also a part of food quality, although these are not measured by the senses of smell, taste, sight, or touch. When one visualizes a spectrum ranging from good to poor quality, the extremes are easily differentiated. This is not true for the central part of the spectrum, however, especially for products in which the manufacturing process tends to mask differences, as with comminuted foods. When foods become more abundant, standards of quality are likely to be higher and more clearly defined. Quality, which is acceptable in one society may not be in another. Chemical indicators may be the only means of evaluating quality in some foods, as processing methods, such as filtration, preclude the use of conventional methods, such as plate counts. In some foods, indicator compounds may supplement microbiological methods of analyzing food quality, including plate counts, mold counts, rot fragment counts, and direct microscopic counts. The use of chemical indicators assists the manufacturer in producing and maintaining high-quality foods. This chapter discusses the background dominant spoilage flora, and chemical indicators of microbial spoilage of: chemical indicators of quality for foods with high protein content, chemical indicators of quality for foods with high fat content, and chemical indicators of quality for foods with high carbohydrate content.

Production of Bacterial and Yeast Biomass in Ground Corn Cob and Ground Corn Stalk Media1

The production of biomass using ground corn cobs and ground corn stalks and a 1:1 (w/w) mixture of the two was studied using Cellulomonas uda in a monoculture and in mixture with Candida utilis . The addition of C. utilis improved the amino acid content of the biomass. With the combination of C. uda and C. utilis , there was more soluble protein in the growth medium. With the addition of C. utilis to the corn cob fermentation, the relative nutritive value increased from 45.7% with a monoculture to 72.6% with a mixed culture. The crude protein also increased from 13.5 g/100 g to 21.1 g/100 g. The ratio of enzyme activity with carboxymethyl cellulose to that of filter paper was about two at the 5th day of fermentation.

Enrichment of ground corn cobs with cellulolytic microorganisms

Abstract Fermentation of ground corn cobs increased their nutritive value after pretreatment with NaOH. Bacterial fermentation improved the vitamin content, total protein, amino acid content, and the percentage relative nutritive value. Fungal fermentation was less effective than bacterial fermentation. The addition of Candid utilis to the bacterial fermentation improved the nutritive value of the fermented material. A mixture of Cellulomonas uda, Trichoderma reesei and C. utilis was not superior to a mixed culture of C. uda and C. utilis but was better than a mixture of T. reesei and C. utilis for achieving improved nutritive value by fermentation.