What is the Difference Between Bioavailability Bioaccessibility and Bioactivity of Food Components?

The preparation of foods fortified with functional components requires integration of diverse aspects under evaluation. These include selecting of the appropriate source, detecting the bioactive compounds, applying separation and recovery techniques, performing toxicological assessments and finally making stability, activity and bioaccessibility measurements. At this point, it is important to define carefully the terms “bioavailability”, “bioaccessibility” and “bioactivity” (Figure 1) that are often used indistinctly to express similar functions.

Bioavailability includes gastrointestinal (GI) digestion, absorption, metabolism, tissue distribution, and bioactivity.  However, it has several meanings depending on the research area used to. For instance, from a pharmacological point of view, bioavailability is the rate and extent to which the therapeutic moiety is absorbed and becomes available at the drug action site. From the nutritional point of view (that is of particular interest in the current book), bioavailability refers to the fraction of the nutrient that is stored or being available in physiological functions. It is a key term for nutritional effectiveness, as not all the amounts of bioactive compounds are used effectively by the organism. For example, when different foods come in contact with the mouth or digestive tract, various interactions may take place affecting phytochemical bioavailability (e.g. fat enhances quercetine bioavailabilty in meals). Therefore, bioavailability expresses the fraction of ingested nutrient or bioactive compound that reaches the systemic circulation and ultimately utilized.

Before becoming bioavailable, bioactive compounds must be released from the food matrix and modified in the GI tract. Thus, bioavailability includes the term bioaccessibility. Indeed, it is important to analyze whether the digestion process affects bioactive compounds and their stability, before concluding on any potential health effect. Bioaccessibility is defined as the quantity of a compound that is released from its matrix in the gastrointestinal tract, becoming available for absorption (e.g. enters the blood stream). This term includes digestive transformations of foods into material ready for assimilation, the absorption/assimilation into intestinal epithelium cells as well as the presystemic, intestinal and hepatic metabolism. However, beneficial effects of unabsorbed nutrients such as calcium binding of bile salts in the tract are missed by definitions based on absorption. Bioaccessibility is usually evaluated by in vitro digestion procedures, generally simulating gastric and small intestinal digestion, sometimes followed by Caco-2 cells uptake.

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Nutraceuticals and Functional Components in Nutrition and Food Products

Foods contain major and minor components as well as bioactive compounds (e.g. antioxidants, peptides, carbohydrates, lipids, glucosinolates) that are of primary importance for human nutrition. Consequently, their importance has initiated a surge of research and product development in the food industry. In order to adapt to these consumer drivers and enhance the physiological functionality of inherent nutrients, the food industry is developing the so-called “functional foods”.

The latest term was born in Japan. Indeed, Japanese were the first to observe that food could have a role beyond gastronomic pleasure and nutrient supply to the human organism. Japan is the first country to legislate these products in the FOSHU (Foods of Specified Health Use) legislation, whereas it has the highest number of functional foods on the market. Europe and the American countries incorporated later this concept.

The American Dietetic Association (ADA) classified in 2004 all food as functional at some physiological level, pointing out that “the term functional food should not be used to imply that there are good and bad foods“. In addition, it denotes that “all food can be incorporated into a healthful eating plan ─ the key being moderation and variety“. Whole foods like fruits and vegetables represent the simplest example of functional foods since they are rich in bioactive compounds that protect body’s cells against oxidative damage and reduce the risk of developing certain cancers.

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How do Emerging Processing Technologies Affect Nutraceuticals and Functional Food Components?

Foods contain major and minor components as well as bioactive compounds that are of primary importance for human nutrition. The importance of these compounds accelerated the development of innovations in the food industry, generating the so-called “functional foods” and “nutraceuticals“. Whole foods like fruits and vegetables represent the simplest example of functional foods, as they are rich in bioactive compounds and have a well-established protective role against the development of diseases.

Nutraceuticals represent any substance that provides medical or health benefits, including the prevention and treatment of diseases. Contrarily to functional foods, nutraceuticals are commodities derived from foods used in the medicinal form of pills or capsules. The preparation of foods fortified with functional components requires integration of diverse aspects under evaluation. These include for instance separation techniques, toxicological assessments, stability and activity tests.

On the other hand, processing has an impact on the final food products. Applied technologies may influence the content and effectiveness of nutrients, e.g. loss of bioactive compounds or diminution of their functionality typically increases more and more as foods are processed, stored and transported.

Novel, non-thermal technologies (e.g. ultrasounds, high-hydrostatic pressure, pulsed electric field, high voltage electrical discharge, cold plasma) promise to treat foods without destroying the nutritional components and sensorial characteristics that are normally affected during heat treatment. The latest techniques are today applied in both research institutes and food industries, promising to shorten processing times, control Maillard reactions, improve products’ quality and enhance functionality. The implementation of these technologies together with other trends and practices of the food industry (e.g. nanoencapsulation, food waste recovery, emerging need for innovations etc.) have brought new developments, data and state of the art in the field.

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