Phenolics in Food and Nutraceuticals is the first single-source compendium of essential information concerning food phenolics. This unique book reports the classification and nomenclature of phenolics, their occurrence in food and nutraceuticals, chemistry and applications, and nutritional and health effects. In addition, it describes antioxidant activity of phenolics in food and nutraceuticals as well as methods for analysis and quantification. Each chapter concludes with an extensive bibliography for further reading. Food scientists, nutritionists, chemists, biochemists, and health professionals will find this book valuable.

Phenolics in food and nutraceuticals

This review defines the range of forms in which cinnamates (p-coumarates, caffeates, ferulates and sinapates) occur in foods and beverages subdividing them into (i) the classic chlorogenic acids and close allies, (ii) other esters, amides and glycosides, and (iii) transformation products formed during processing. Cinnamate derivatives which would not release cinnamic acid by hydrolysis are excluded. The quantitative data are reviewed concisely and attention is drawn to certain shortcomings, in particular a complete absence of data for certain commodities (breakfast cereals, baked goods, tomato products and nuts) and minimal data for pulses, legumes and processed or cooked foods. In addition, more data are required for the edible portion of modern varieties. By extrapolating from such data as are available the important source(s) (i) of individual cinnamates (regardless of the conjugate type) and (ii) of each major class of conjugate, have been identified as follows: (i) Cinnamates: caffeic acid: coffee beverage, blueberries, apples, ciders; p-coumaric acid: spinach, sugar beet fibre, cereal brans; ferulic acid: coffee beverage, citrus juices, sugar beet fibre, cereal brans; sinapic acid: broccoli, kale, other leafy brassicas, citrus juices. (ii) Conjugates: caffeoylquinic acids: coffee beverage, blueberries, apples, ciders; p-coumaroylquinic acids: sweet cherries; feruloylquinic acids: coffee beverage; tartaric conjugates: spinach, lettuce, grapes and wines; malic conjugates: lettuce, spinach, possibly legumes; rosmarinic acid: culinary herbs, mixed herbs, possibly stuffings; cell wall conjugates: spinach, sugar beet fibre, cereal brans. It seems likely that the UK population will fall into several categories depending on (i) their consumption of coffee, (ii) their consumption of bran, and (iii) their consumption of citrus. Those who drink several cups of coffee per day augmented by bran and citrus might easily ingest 500-800mg cinnamates (or even 1 g for the greatest coffee ingest consumption) whereas those who eschew all these and take little fresh fruit or vegetables might struggle to consume 25 mg.

Chlorogenic acids and other cinnamates – nature, occurrence and dietary burden

Interest in food colorants as shown by the number of patents has doubled in recent years with natural pigments outnumbering synthetics by five to one The natural colorant area can be subdivided into anthocyanins, betalains, chlorophylls, carotenoids, flavonoids, polyphenols, Monascus, hemes, quinones, biliproteins, safflower, turmeric, and miscellaneous All involve different groups of chemical compounds which may be used directly as colorants, or may be chemically modified to produce different hues or increased stability All usually involve a method of collection, extraction, purification, possibly stabilization, and formulation A variety of hues can be obtained ranging from green through yellow, orange, red, blue, and violet, depending on the source of colorant Similarly, water or oil‐soluble formulations can be prepared depending on the type of colorant

Food colorants: Anthocyanins

Antimicrobials are classified as traditional when they (i) have been used for many years, (ii) are approved by many countries for inclusion as antimicrobials in foods (e.g., lysozyme and lactoferrin, which are naturally occurring but regulatory-agency approved), or (iii) are produced by synthetic means (as opposed to natural extracts). Many organic acids are used as food additives, but not all have antimicrobial activity. Research suggests that the most active are acetic, lactic, propionic, sorbic, and benzoic acids. Acetic acid was the most effective antimicrobial in ground roasted beef slurries against Escherichia coli O157:H7 growth in comparison with citric or lactic acid. Sorbate is applied to foods by direct addition, dipping, spraying, dusting, or incorporation into packaging. The mechanism by which dimethyl dicarbonate (DMDC) acts is most likely related to inactivation of enzymes. A related compound, diethyl dicarbonate, reacts with imidazole groups, amines, or thiols of proteins. Lysozyme is most active against gram-positive bacteria, most likely because the peptidoglycan of the cell wall is more exposed. The primary use for sodium nitrite as an antimicrobial is to inhibit Clostridium botulinum growth and toxin production in cured meats. Sulfites may be used to inhibit acetic acid-producing bacteria, lactic acid bacteria, and spoilage bacteria in meat products. In the future, traditional food antimicrobials will continue to play an important role in food preservation.

Chemical Preservatives and Natural Antimicrobial Compounds

Many factors contribute to a successful natural fermentation of carbohydrate-rich food and feed products. Metabolic activities of lactic acid bacteria (LAB) play a leading role. Their ability to rapidly produce copious amounts of acidic end products with a concomitant pH reduction is the major factor in these fermentations. Although their specific effects are difficult to quantitate, other LAB metabolic products such as hydrogen peroxide and diacetyl can also contribute to the overall antibiosis and preservative potential of these products. The contribution of bacteriocins is also difficult to evaluate. It is suggested that they may play a role in selecting the microflora which initiates the fermentation. Bacteriocins are believed to be important in the ability of LAB to compete in non-fermentative ecosystems such as the gastro-intestinal tract. During the past few decades interest has arisen in the use of the varied antagonistic activities of LAB to extent the shelf-life of protein-rich products such as meats and fish. Recent findings indicate that the newly discovered Lactobacillus reuteri reuterin system may be used for this purpose.

Antagonistic activities of lactic acid bacteria in food and feed fermentations.

The antifungal activities of caffeic, p-coumaric, ferulic, and chloro-genie acids against Saccharomyces cerevisiae were investigated. Caffeic acid was found to exhibit little inhibition of growth, although the lag period was extended in the presence of 1000 ppm. Chloro-genie acid had no effect on the organism. In contrast, p-coumaric acid at 100 ppm increased the lag phase of S. cerevisiae, and above 250 ppm, inhibition after 72 hr growth was proportional to the concentration present. Ferulic acid caused an increase in lag phase at 50 ppm, while as little as 250 ppm resulted in complete inhibition. These results suggest that naturally occurring hydroxycinnamates may interfere with the fermentation of fruits by this yeast.

INHIBITION OF Saccharomyces cerevisiae BY NATURALLY OCCURRING HYDROXYCINNAMATES

SUMMARY— Growth rate studies were conducted with Pseudomonas aeruginosa to measure the inhibitory effect of CO2 when such variables as temperature, O2, tension, pH, and ionic strength of the glucose-salts medium were controlled. Depletion of O2 did not limit growth until more than 75% (v/v) of the air was replaced with nitrogen. Generation time increased with ionic strength of the medium. The influence of pH in the range of 6.0 to 7.4 on the growth rate was negligible. When these variables were controlled, a linear relationship between generation time and CO2 composition of the gas phase was observed. At 70% CO2 (v/v), the generation time was nearly doubled. Thus, CO2 inhibits the metabolism of the organism, and this inhibition is due to gaseous CO2 in the air only when other environmental factors are controlled.

Growth Inhibition of a Pseudomonas by Carbon Dioxide

INFLUENCE OF CARBON DIOXIDE UPON THE METABOLISM OF Pseudomonas aeruginosa

Thermal stability of lipoxygenase (LOX) and peroxidase (POD) in fresh asparagus tips and partially purified asparagus LOX and POD were compared. In all cases, heating at 50, 60 and 70°C resulted in higher percentages of residual LOX activity than POD activity. Inactivation of LOX followed first order kinetics while inactivation of POD followed a biphasic curve. Activation energies for thermal denaturation of the partially purified enzymes were 47.5 kcal/mol for LOX and 41.9 kcal/mol for POD.

Thermal Inactivation of Asparagus Lipoxygenase and Peroxidase

SUMMARY—
Changes in firmness, protein, pectinesterase (PE) and polygalacturonase (PG) were followed during enlargement, maturation, and abnormal ripening of the Bartlett pear (Pyrus communis) on the tree. Although the PE activity per pear increased during maturation, with a good correlation with total weight (r= 0.93 and 0.87 for 1962 and 1963), the amount of activity per gram fresh weight and per milligram protein decreased. There was a high correlation between PE activity and protein (r= 0.84 and 0.91 for 1962 and 1963). The specific activity of the enzyme decreased during maturation. As the fruit matured and ripened on the tree, the percent recovery of PE decreased. The use of polyvinylpyrrolidone in the extraction procedure to adsorb the phenolic compounds counteracted this trend. It was concluded that the small changes in PE activity could not account for the changes in esterification of pectin observed by other investigators. Variable results were obtained with the PG assays. Weak PG activity was observed in the immature fruit in 1962 and 1963. No activity was observed in 1966, even in the presence of polyvinylpyrrolidone.

C. W. Nagel

Papers

INHIBITION OF Saccharomyces cerevisiae BY NATURALLY OCCURRING HYDROXYCINNAMATES

Growth Inhibition of a Pseudomonas by Carbon Dioxide

INFLUENCE OF CARBON DIOXIDE UPON THE METABOLISM OF Pseudomonas aeruginosa

Thermal Inactivation of Asparagus Lipoxygenase and Peroxidase

Pectic Enzymes and Development of the Pear (Pyrus communis)