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

Anthocyanins and betalains play important roles both in plant physiology, visual attraction for pollinators and seed dispersers, but also in food mainly defining its aesthetic value. Since anthocyanin and betalain structures allow to predict only part of their appearance, additional chemical and anatomical functions are required to modulate the appearance of plants and coloured food. Physiological effects that the same pigments exert in plants are supposedly similar to those which they show in humans following ingestion of coloured food. Therefore, anthocyanins and betalains both in fresh and also processed fruit and vegetables serve two functions: They improve the overall appearance, but also contribute to consumers' health and well-being.

Functional properties of anthocyanins and betalains in plants, food, and in human nutrition

Exploitation of natural products as an alternative strategy to control postharvest fungal rotting of fruit and vegetables

Postharvest heat treatments

Fresh food products can be processed using UV light as a germicidal medium to reduce the food-borne microbial load. Water has been treated with UV light to obtain drinking water for quite some time. Pumpable fruit and vegetable products are generally very suitable for processing by UV light to reduce the microbial load. Today, most of these products are pasteurised to obtain microbiologically safe and nutritious products. However, pasteurisation can change the taste and flavour of such products because of the temperature and processing time. Juices from different sources can be treated by exposure to UV light at different doses. On the other hand, variables such as flow rate, exposure time, type of fruit product, juice colour and juice composition, among other variables, need to be studied to obtain fruit products with reduced microbial load, increased shelf life and adequate sensory and nutritional characteristics. Reduction of microbial load through UV light application as a disinfection medium for food products other than liquids is also being studied. Moreover, UV technology could be a source for pasteurisation of liquids, or disinfection of solid foods as an alternative technology, instead of thermal treatment or application of antimicrobial compounds.

Advantages and Limitations on Processing Foods by UV Light

http://directory.umm.ac.id/Data%20Elmu/jurnal/P/Postharvest%20Biology%20and%20Technology/Vol21.Issue1.2000/1755.pdf

Host–pathogen interactions modulated by heat treatment

Storage performance of Fortune mandarins following hot water dips

Cactus Pear Fruit Production

Extensive research has been done in recent years to reduce the heavy dependence on chemical fungicides to control postharvest diseases and disorders of horticultural crops. Alternative strategies were based on improved cultural practices, biological control, plant-defense promoters, and physical treatments such as UV illumination, radiofrequency treatment, heat therapy, and storage technologies. Among these, postharvest heat treatments such as hot water dips, short hot water rinsing and brushing, and hot air conditioning have reduced rot development and enhanced fruit resistance to chilling injury in sensitive cultivars while retaining fruit quality during cold storage and shelf life. Additive or synergistic increases in effectiveness were observed by integrating heat therapy with various chemical compounds, thus leading to significant reductions in the application of active ingredients to protect produce from decay. This paper highlights the knowledge on this topic with emphasis on heat therapy effects and factors affecting the uptake, persistence, and performance of fungicide residues when they are applied in combination with hot water.

Control of postharvest diseases of fruit by heat and fungicides: efficacy, residue levels, and residue persistence. A review.

ADDITIONAL INDEX WORDS. Citrus sinensis, cold storage, decay, phytoalexins, 6,7-dimethoxycoumarin, 7-hydroxy 6- methoxycoumarin ABSTRACT. 'Washington Navel', 'Biondo Comune', 'Tarocco', and 'Valencia Late' orange ( Citrus sinensis (L.) Obsek) fruit, harvested at various periods of time, were subjected to ultraviolet-C (UV-C) irradiation at 0.5, 1.5, or 3.0 kJ·m -2 doses and then stored at 7 °C and 90% to 95% relative humidity (RH) for 4 weeks plus one additional week at 20 °C and ≈80% RH. Following UV-C treatment, there was varying amounts of rind browning and necrotic peel damage, depending on cultivar, treatment dose, and harvest date. 'Tarocco' fruit were damaged more easily by UV-C treatment than the other cultivars. 'Valencia L.' were the most resistant to UV-C irradiation, showing no adverse effects at the lowest dosage and having the lowest percentages of damaged fruit at higher dosages. 'Washington Navel' and 'Biondo Comune' oranges showed an intermediate susceptibility to UV-C treatment, with negligible differences between these cultivars. The percentage of damaged fruit after irradiation at the higher UV-C dosages decreased in most fruit samples as the season progressed. UV-C irradiation at 0.5 kJ·m -2 effectively reduced decay development compared with nontreated fruit. Irradiation with 1.5 kJ·m -2 was more effective compared with 0.5 kJ·m -2 only in early harvested fruit. In 'Washington Navel' and 'Biondo Comune' oranges in the later harvests, treatment with 3.0 kJ·m -2 improved decay control further, compared with 0.5 kJ·m -2 . Following UV-C treatments the phytoalexins, scoparone and scopoletin, accumulated in flavedo tissue depending on the cultivar, fruit age, and UV-C treatment. Both phytoalexins displayed a similar accumulation pattern, however, the levels of scopoletin were very low compared with scoparone. Concentrations of phytoalexins rose as the irradiation dose increased. No scoparone and scopoletin could be detected in nontreated fruit. The highest concentration of phytoalexins among cultivars was recorded in 'Valencia Late' oranges, the lowest in 'Tarocco', with similar intermediate accumulations in 'Washington Navel' and 'Biondo Comune'. In 'Washington Navel', 'Biondo Comune', and 'Tarocco' oranges, the rate of scoparone accumulation was significantly higher in fruit harvested earlier in the season while 'Valencia late' oranges exhibited an opposite trend.

/pdf/scoparone-and-scopoletin-accumulation-and-ultraviolet-c-40oktnp5mf.pdf

Mario Schirra

Papers

Host–pathogen interactions modulated by heat treatment

Storage performance of Fortune mandarins following hot water dips

Cactus Pear Fruit Production

Control of postharvest diseases of fruit by heat and fungicides: efficacy, residue levels, and residue persistence. A review.

Scoparone and Scopoletin Accumulation and Ultraviolet-C Induced Resistance to Postharvest Decay in Oranges as Influenced by Harvest Date