Effect of gamma and electron beam irradiation on the physico-chemical and nutritional properties of mushrooms: a review

The short shelf-life of mushrooms is an obstacle to the distribution and marketing of the fresh product. Thus, prolonging postharvest storage, while preserving their quality, would benefit the mushroom industry as well as consumers. There has been extensive research on finding the most appropriate technology for mushrooms preservation. Gamma, electron-beam and UV irradiation have been shown to be potential tools in extending the postharvest shelf-life of fresh mushrooms. Studies evaluating the effects of ionizing radiation are available mainly in cultivated species such as Agaricus bisporus, Lentinus edodes and Pleurotus ostreatus. This review comprises a comprehensive study of the effects of irradiation on physico-chemical parameters (weight, colour, texture and pH), chemical compounds including nutrients (proteins, sugars and vitamins) and non-nutrients (phenolics, flavonoids and flavour compounds), and on biochemical parameters such as enzymatic activity of mushrooms for different species and from different regions of the world.The authors are grateful to the Foundation for Science and Technology (FCT, Portugal) for financial support to the research centers CIMO (PEst-OE/AGR/UI0690/2011) and REQUIMTE (PEst-C/EQB/ LA0006/2011). A.S. Fernandes and A.L. Antonio thank FCT, POPHQREN and FSE for their Grants (SFRH/BD/76019/2011 and SFRH/ PROTEC/67398/2010, respectively)

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

24 pages, 4 tables.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.The authors are grateful to the Spanish CICYT (projects ALI97-0681, ALI98-0843 and AGL2000-2014) for financial support of this work. Dr. Juan Carlos Espín is holder of a postdoctoral contract from the Spanish Ministerio de educación Cultura y Deporte (project IFD97-1337-C02-01)Peer reviewe