Tomás-Barberán / Gil Improving the Health-Promoting Properties of Fruit and Vegetable Products

1. Auflage 2008
ISBN: 978-1-84569-428-9
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: Adobe DRM (»Systemvoraussetzungen)

E-Book, Englisch, 584 Seiten

Reihe: Woodhead Publishing Series in Food Science, Technology and Nutrition

Consumers are advised to increase fruit and vegetable consumption, but the health effects of increased intake are not fully understood. This important collection brings together information on the health-promoting properties of fruit and vegetables.Introductory chapters provide an overview of fruit and vegetable bioactives and consumer attitudes towards fruit and vegetables. Part two discusses the health effects of fruit and vegetables in relation to specific diseases, including cancer, cardiovascular disease, diabetes, obesity and neurodegenerative diseases. The focus in Part three is on understanding fruit and vegetable phytochemicals. Chapters cover physiological and ecological functions and biosynthesis of health-promoting compounds in fruit and vegetables, rapid analysis of phytochemicals in fruit and vegetables and clinical evidence for biological activity of fruit and vegetable phytochemicals.Part four chapters review the effect of pre- and post-harvest technologies on the health-promoting properties of fruit and vegetables. Topics covered include traditional breeding and modern processing techniques and their effect on fruit and vegetable phytochemicals; genetic manipulation of vegetable crops to alleviate diet-related diseases; agronomy and the nutritional quality of fruit; storage and handling of fruit and vegetables for optimal health-related quality and postharvest enhancement of bioactive compounds in fresh produce using abiotic stresses. The final chapters in Part five look at the nutritional quality of particular fruit and vegetable products, such as fresh-cut fruit and vegetables and organic fruit and vegetables.Improving the health-promoting properties of fruit and vegetable products is a valuable reference for those working in the fresh and processed fruit and vegetable sector of the food industry. - Provides an overview of fruit and vegetable bioactives - Discusses the health effects of fruit and vegetables in relation to specific diseases - Reviews the impact of agronomy, post-harvest treatments and processing on the nutritional quality of fresh fruit and vegetables

Autoren/Hrsg.

Tomás-Barberán, F A

Gil, M I

Leseproben

Introduction
Francisco A. Tomás-Barberán; María I. Gil Fruit and vegetables as a source of health
Fruit has been the inspiration of artists and its consumption has been associated with healthy dietary habits since ancient times. References to fruits such as grapes, pomegranates, dates and apples are frequent in the Bible, Koran and Torah. In many cases, these fruits are associated with eternal life as in ancient Egyptian and Sumerian cultures. Modern epidemiology shows that fruit and vegetable consumption reduces the risk of several chronic diseases, such as cardiovascular diseases and certain types of cancer (Hung et al., 2004). This has powered the interest of researchers in determining the biological activity of fruit and vegetable constituents. In addition to vitamins, minerals and dietary fibre, these foods provide a whole range of non-nutrient constituents that are considered biochemically to be secondary metabolites, and that have been suggested as being responsible, at least partly, for the health benefits associated with the regular consumption of fruit and vegetables. These secondary metabolites include different chemical families such as terpenoids (carotenoids, essential oils, steroids, etc.), nitrogen and sulphur-containing compounds (glucosinolates of the Brassicaceae and sulphur compounds of the Allicaceae) and phenolic compounds. This last group includes many different metabolites ranging from the very simple aromatic acids, such as p-hydroxy-benzoic acid, to complex oligomers and polymers as in the case of procyanidins, gallotannins and ellagitannins. Combinations with different sugars and aliphatic and aromatic acids, as well as glucuronides and sulphates are also common. The biological activity of these compounds is often related to their antioxidant capacity or their ability to neutralize free radicals that are the origin of many of the age-related diseases previously mentioned. Plant secondary metabolites are, in addition, responsible for quality characteristics of plant-derived food products, including colour and appearance, flavour and aroma, etc. (Tomás-Barberán and Espín, 2001). Traditional plant breeding aimed to increase the yield and decrease the anti-nutrient constituents, such as bitter and astringent compounds, of fruits and vegetables. These anti-nutrient secondary metabolites are known to act as natural feeding deterrents, anti-fungal and anti-microbials and, therefore, the selected fruit and vegetable cultivars were more sensitive to diseases. As a result, the use of artificial chemicals to fight pests and microbial diseases became a general agronomic practice. More recently fruit and vegetable cultivars have also been selected to extend their postharvest life and improve their attributes for storage and transportation. This selection strategy often leads to a poorer taste and aroma, this being one of the main consumer complaints regarding fruit and vegetable quality. Nowadays the breeding and selection challenge is the search for new cultivars in which the traditional taste and aroma are recovered, enhancing in addition the content of health-promoting compounds and decreasing the need for synthetic chemicals to fight plant pests and diseases. In this book, the different strategies for increasing the health-promoting properties of fruits and vegetables are explored. In the Introduction, the health-promoting phytochemicals present in fruit and vegetables are presented as well as the consumer attitude towards these food products. Successful examples of the way fruits can be marketed are shown and the specific effects of fruit and vegetable consumption on cardiovascular diseases, diabetes, obesity, cancer and neurodegenerative diseases are described in a second part of the book. In the third part, the biological and biochemical aspects of health-promoting compounds in fruit and vegetables are reviewed. The fourth part of the book covers different ways of enhancing the content of bioactive metabolites in fruit and vegetables by plant breeding and genetic manipulation of crops and how the different agronomic practices can affect the content of these bioactive phytochemicals. The effect of postharvest storage and processing on these metabolites is also covered in this part of the book as well as different postharvest technological treatments that can be used to induce the biosynthesis of these health-promoting compounds in fruits and vegetables. In the last part, the content of health-promoting compounds in different food products is reviewed, including fresh-cut products that are becoming more and more popular in our diet, organic agriculture products and the extracts prepared from fruit and vegetables for the preparation of functional foods. There are, however, a few points that have not been covered in the book and that may be relevant in terms of the biological activity of these food products. One is the bioavailability and metabolism of the bioactive compounds. The other is the way commodities are stored and prepared by the consumer, as well as consumer food choices and preferences which have a large impact on the phytochemicals ingested in the diet. Some questions may arise after reading this book. One is whether it is better for our health to eat fruit and vegetables raw rather than processed. Experimental results show that thermal processing generally decreases the content of bioactive compounds, probably as a result of oxidation processes. Processing, however, can also increase the bioavailability of bioactive compounds, as is the case of lycopene whose bioavailability is higher after the intake of processed tomato paste than from raw tomato (Unlu et al., 2007). Processing also enhances the release of ellagic acid from raspberry ellagitannins during jam manufacturing and can modulate the bioavailability of this bioactive polyphenol (Zafrilla et al., 2001). Bioavailability and metabolism should be taken into consideration in all studies regarding the determination of the biological activity of fruit and vegetable phytochemicals. Many studies evaluate the biological activity of the compounds present in food using in vitro systems. These studies can lead to doubtful conclusions as these phytochemicals are often poorly absorbed and widely metabolized. In these cases, the metabolites should be studied for the different biological activities associated with the consumption of fruit and vegetables. In addition, the concentrations assayed in most studies are often much higher than those encountered in a dietary approach. In these cases it is crucial to know the metabolism of the naturally occurring compounds, and identify the metabolites that are finally absorbed. It is also important to understand the way they are conjugated by Phase II enzymes, and the concentration they reach in plasma and in target tissues. As an example, it is irrelevant testing the biological activity of the polyphenols present in bilberry juice on in vitro cultures of lung cancer cells as their bioavailaibility is poor, the juice phytochemicals do not reach the lung tissues at significant concentrations and extensive metabolism of these phytochemicals occurs in the intestine. Consumer preferences also have a marked impact on the intake of health-promoting compounds from fruit and vegetables. Selecting the white parts of the lettuce and discarding the external green tissues for preparation of salads decreases dramatically the intake of potentially bioactive phytochemicals. Peeling the fruit before consumption, as in the case of apples, peaches, apricots, plums or tomatoes, also decreases the phytochemicals intake and, in some groups of phytochemicals, peeling eliminates them from the diet, as is the case of flavonols that are almost exclusively located in the peel. The way in which oranges are peeled can also affect the intake of flavanones from this fruit. The part of the orange richest in flavanones is the albedo (the white tissue between the flavedo and the fruit segments). Thus, a thorough peeling to remove completely the albedo decreases significantly the intake of flavanones. Peeling and discarding the seeds of grapes, also decreases the intake of antioxidant phytochemicals. Steam cooking vegetables always preserves a higher content of phytochemicals in the tissue than boiling and removing the water before serving. As an example of the impact of consumer preferences on phytochemical intake, the amount of polyphenols ingested after selecting five fruit and vegetables servings to follow the ‘5 a day’ recommendation has been evaluated in Table 1. Oranges, grapes, peaches, lettuce and spinach were selected. Thus, if a consumer selects a procyanidins-rich peach cultivar and eats it un-peeled, the intake of antioxidant phenolics will be as much as 10 times higher than of a cultivar poor in procyanidins and that is peeled before consumption. If the peel and seeds of ‘Napoleon’ grapes are removed, the antioxidant polyphenol intake decreases 10-fold. If a ‘Navel’ orange is peeled to remove all the white tissue (albedo), the flavanone intake is reduced four-fold. If the consumer selects for the preparation of a salad the white midribs of ‘Iceberg’ lettuce instead of having ‘Lollo rosso’, the polyphenol intake can be reduced as much as 30-fold. And, if spinach leaves are boiled in water and the cooking waters are discarded, half of the spinach antioxidants are lost when compared with the same vegetable cooked in steam, as this preserves antioxidant polyphenols in the cooked tissues. This means that for the same...