Phenolic secondary metabolites play an important role in plant-derived food quality, as they affect quality characteristics such as appearance, flavour and health-promoting properties. Their content in foods is affected by many factors that influence phenolic stability, biosynthesis and degradation. In terms of their biosynthesis the key enzyme phenylalanine ammonia-lyase (PAL) is especially relevant, as it can be induced by different stress (environmental) conditions. In addition, polyphenol oxidases (PPO) and peroxidases (POD) are the main enzymes responsible for quality loss due to phenolic degradation. The different factors affecting phenolic-related food quality are reviewed. These include internal (genetic) and environmental (agronomic) factors, technological treatments applied during postharvest storage of fruits and vegetables, as well as processing and storage of the processed products. The different strategies that are required to either maintain or enhance the phenolic-related quality of foods are critically reviewed. Genetic modification designed to decrease polyphenol oxidases or peroxidases is not always a feasible method, owing to side problems related to the growth and defence of the plant. Agronomic treatments can be used to enhance the phenolic content and pigmentation of fruits and vegetables, although the information available on this topic is very scarce and even contradictory. Some postharvest treatments (cold storage, controlled or modified atmospheres, etc) can also improve phenolic-related quality, as well as new processing methods such as irradiation (gamma, UV), high-field electric pulses, high hydrostatic pressures and microwaves. Les composes phenoliques, metabolites secondaires des plantes, jouent un role dans la qualite des fruits, au niveau de l'apparence, de la flaveur et des qualites nutritives. L'enzyme cle de leur biosynthese est la phenylalanine ammonium-lyase, regulee par les facteurs environnementaux. La polyphenol oxydase et la peroxydase sont responsables des degradations donc des pertes de qualite. Les differents facteurs internes (genetiques) et externes (agronomiques) affectant la qualite des produits vegetaux sont etudies. Les differentes mesures envisageables (modification genetique, traitements chimiques ou physiques apres recolte) pour modifier le contenu en compose phenoliques et donc la qualite des produits vegetaux sont etudies.

Phenolic compounds and related enzymes as determinants of quality in fruits and vegetables

Pulse proteins: Processing, characterization, functional properties and applications in food and feed

Starch retrogradation is a process in which disaggregated amylose and amylopectin chains in a gelatinized starch paste reassociate to form more ordered structures. Starch retrogradation has been the subject of intensive research over the last 50 years, mainly due to its detrimental effect on the sensory and storage qualities of many starchy foods. However, starch retrogadation is desirable for some starchy food products in terms of textural and nutritional properties. To better understand the effect of starch retrogradation on the quality of starchy foods, measurement methods of starch retrogradation and factors that influence starch retrogradation have been studied extensively. This article provides a comprehensive review of starch retrogradation including the definition of the process, molecular mechanisms of how it occurs, and measurement methods and factors that influence starch retrogradation. The review also discusses the effect of retrogradation on the in vitro enzyme digestibility of starch. Spectroscopic methods such as FTIR and Raman are considered to be very promising in characterizing starch retrogradation at a molecular level, although more studies are needed in the future.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/1541-4337.12143

Starch retrogradation: a comprehensive review

Coffee is a complex mixture of chemicals that provides significant amounts of chlorogenic acid and caffeine. Unfiltered coffee is a significant source of cafestol and kahweol, which are diterpenes that have been implicated in the cholesterolraising effects of coffee. The results of epidemiological research suggest that coffee consumption may help prevent several chronic diseases, including type 2 diabetes mellitus, Parkinson’s disease and liver disease (cirrhosis and hepatocellular carcinoma). Most prospective cohort studies have not found coffee consumption to be associated with significantly increased cardiovascular disease risk. However, coffee consumption is associated with increases in several cardiovascular disease risk factors, including blood pressure and plasma homocysteine. At present, there is little evidence that coffee consumption increases the risk of cancer. For adults consuming moderate amounts of coffee (3‐4 cups/d providing 300‐400 mg/d of caffeine), there is little evidence of health risks and some evidence of health benefits. However, some groups, including people with hypertension, children, adolescents, and the elderly, may be more vulnerable to the adverse effects of caffeine. In addition, currently available evidence suggests that it may be prudent for pregnant women to limit coffee consumption to 3 cups/d providing no more than 300 mg/d of caffeine to exclude any increased probability of spontaneous abortion or impaired fetal growth.

https://www.tandfonline.com/doi/pdf/10.1080/10408390500400009

Coffee and Health: A Review of Recent Human Research

Polyphenol oxidases in plants and fungi: going places? A review.

Changes in the browning of apple juice, polyphenol content, and polyphenol oxidase were examined during apple ripening. The degree of browning of apple juice, the phenol content per gram of flesh, and the polyphenol oxidase (PPO) activity per milligram of protein decreased during ripening. From 4.5 to 6 months after flowering, the amount of PPO per milligram of protein, determined by an enzyme-linked immunosorbent assay, was constant, but its specific activity decreased, suggesting that PPO had denatured. PPO was uniformly distributed in the immature and mature apple, but active PPO was mainly localized around the core in the mature apple.

Relationship between Apple Ripening and Browning: Changes in Polyphenol Content and Polyphenol Oxidase

The use of germinated cereals and legumes in reducing bulk of weaning foods was investigated. The blends were formulated and studied for their viscosity, acceptability, and quality. Germinated rice-mung-bean, germinated rice-cowpea, germinated corn-mungbean and germinated corn-cowpea (germination period was 72 hr for rice/corn and 48 hr for mungbean/cowpea) indicated viscosity reduction from about 20,000 cps to about 3,000 cps at the 70:30 ratio with concomitant good scores in general acceptability. About 400 mL gruel prepared from the formulations met l/3 RDA for protein and energy requirements of infants. The products were found stable for 6 months, mi-crobially safe, and well-tolerated by the infants.

Technology of Weaning Food Formulations Prepared from Germinated Cereals and Legumes

Cut lettuce stored at 4°C gradually turned brown on the cut section after several days of storage Three factors for enzymatic browning, the polyphenol content, polyphenol oxidase activity, and phenylalanine ammonia-lyase (PAL) activity, were examined during the cold storage of cut lettuce A relationship between the browning and PAL activity was apparent We tried to prevent this browning by using the two enzyme inhibitors, 2-aminoindane-2-phosphonic acid (AIP), an inhibitor of the phenylpropanoid pathway, and glyphosate, an inhibitor of the shikimate pathway AIP and glyphosate significantly inhibited the browning of cut lettuce The polyphenol content and PAL activity were both reduced by the treatment with AIP These results show that regulating the biosynthesis of polyphenols is essential to prevent the browning of cut lettuce

Relationship between the enzymatic browning and phenylalanine ammonia-lyase activity of cut lettuce, and the prevention of browning by inhibitors of polyphenol biosynthesis.

Analysis of the tastes of brown rice and milled rice with different milling yields using a taste sensing system

Polyphenol oxidase (PPO) is responsible for enzymatic browning of apples. Apples lacking PPO activity might be useful not only for the food industry but also for studies of the metabolism of polyphenols and the function of PPO. Transgenic apple calli were prepared by using Agrobacterium tumefaciens carrying the kanamycin (KM) resistant gene and antisense PPO gene. Four KM-resistant callus lines were obtained from 356 leaf explants. Among these transgenic calli, three calli grew on the medium containing KM at the same rate as non-transgenic callus on the medium without KM. One callus line had an antisense PPO gene, in which the amount and activity of PPO were reduced to half the amount and activity in non-transgenic callus. The browning potential of this line, which was estimated by adding chlorogenic acid, was also half the browning potential of non-transgenic callus.

Seiichi Homma

Papers

Relationship between Apple Ripening and Browning: Changes in Polyphenol Content and Polyphenol Oxidase

Technology of Weaning Food Formulations Prepared from Germinated Cereals and Legumes

Relationship between the enzymatic browning and phenylalanine ammonia-lyase activity of cut lettuce, and the prevention of browning by inhibitors of polyphenol biosynthesis.

Analysis of the tastes of brown rice and milled rice with different milling yields using a taste sensing system

A Transgenic Apple Callus Showing Reduced Polyphenol Oxidase Activity and Lower Browning Potential