The effect of peroxidase on food flavor and quality is discussed, and its use as an index of blanching fruits and vegetables reviewed. Peroxidase is considered the most heat stable enzyme in plants. If inactivated, all ofher enzyme systems are usually inactivated in the product. There is an empirical relationship between residual peroxidase activity and the development of off-flavors and off-odors in foods. Peroxidase activity has been detected in products stored at — 18°C and under moisture conditions as low as 12.5% moisture. Any activity detected following severe heat treatments is usually due to the enzyme not being wholly inactivated. Inadequate thermal processing may result in regeneration of the enzyme.

Peroxidase and its relationship to food flavor and quality: a review

Publisher Summary This chapter is concerned with two types of oxidative changes that occur in meat: oxidation of the fat, resulting in rancidity; and oxidation of the heme pigments, resulting in discoloration. The two are closely related. In fact, each can accelerate the other, but each can also proceed independently of the other. Together they account for a large part of the economic loss due to substandard or spoiled meat. The chapter devotes to the more fundamental work on these reactions and their interrelationships in meat as it is believed that control can best be achieved when the causes of deterioration are thoroughly understood. In general, the oxidative changes discussed are those of chemical rather than microbiological origin, although it is recognized that the same changes are often brought about by bacteria, and it is not always possible to determine whether bacteria are implicated. The chapter presents facts that contradict simple assumptions such as the idea that the fresh meat of any species is a more or less uniform starting point for experimentation and the idea that the various oxidations that occur in meat, resulting in off-odors, off-flavors, and discolorations, could be lumped together for purposes of control.

Oxidative rancidity and discoloration in meat.

A process and apparatus for a method for reducing the amount of acrylamide in thermally processed foods. This invention permits the production of foods having significantly reduced levels of acrylamide. The method relies on the manipulation of various unit operations used in the production of food products, particularly the washing and cooking unit operations. For example, the washing unit operation can be modified to provide a contacting step at an increased time and temperature, and adding components such as calcium chloride and L-cysteine to an aqueous solution used for the contacting. The cooking unit operation can be modified by dividing it into at least a higher-temperature first heating step and a lower-temperature second heating step in order to avoid the high-temperature/low-moisture conditions most favorable for acrylamide formation.

Method for reducing acrylamide formation in thermally processed foods

The history of the esters of p-hydroxybenzoic acid and their uses as preservatives in pharmaceuticals, cosmetics, foods, and industrial products are discussed. Antimicrobial studies show that the methyl, ethyl, propyl, and butyl esters are effective in low concentrations against fungi and Gram-positive bacteria, but less effective against Gram-negative bacteria. The esters are more fungistatic than fungicidal. The p-hydroxybenzoates were also tested against microorganisms in the presence of humans serum, and against the growth of A. niger in procaine nicillin suspensions. The physical and chemical proprties of the p-hydroxygnwates are extensively described, as well as methods of incorporation and a method of determination by ultraviolet absorption.

p-Hydroxybenzoic Acid Esters as Preservatives: I. Uses, Antibacterial and Antifungal Studies, Properties and Determination

A wide range of color, sugar, and acid composition was found among 12 peach (Prunuspersica (L.) Batsch) genotypes. Among the high-acid genotypes, a trend of increasing Hunter 'a' values, fructose, soluble solids concen- tration (SSC) : titratable acidity (TA) ratio, and decreasing TA and citric acid levels was noted with decreasing mesocarp firmness. Mesocarp firmness was correlated with both skin and flesh 'a' values within all genotypes. Among genotypes, the Hunter 'a'/firmness relationship varied. 'Elberta', a cultivar known to retain a greenish ground color, had a lower Hunter 'a' value when soft than did more recent releases such as 'Dixiland', 'Redhaven', and 'Suwanee'. 'Sam Houston', a low-acid cultivar, had lower TA and malic, citric, and quinic acid levels than the other cultivars. The dominant acid for all genotypes was malic (50% to 60% of total) with about equal amounts of citric and quinic. Soluble sugars included sucrose (54% of total), fructose (31%), and glucose (15%). 'Sam Houston' had lower SSC, a higher percentage of sucrose, lower levels of glucose and fructose, but the same relative sweetness values as the high-acid cultivars. Various compositional and visual attributes of diverse peach cultivars have been researched to establish easily applied char- acteristics to judge the proper harvest period. Ground color (skin or flesh), defined via the Hunter tristimulus 'a' parameter, and fruit firmness have been employed to judge the maturity of peaches (Delwiche and Baumgardner, 1983, 1985; Kader et al., 1982; Rood, 1957). Negative 'a' values indicate more relative greenness and positive 'a' values indicate more red or less green. Studies on 13 commercial fresh-market peaches indicated that at a preripe firmness of 52 N the 'a' value for ground color was distributed within a range of - 7.0 to - 4.4. At 45 N firmness, the range was - 4.7 to - 1.7 (Delwiche and Baumgardner,

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Morris B. Jacobs

Papers

The Chemistry and technology of food and food products