Читать книгу Whole Grains and Health - Группа авторов - Страница 57

Dry fractionation processes have been developed based on know‐how mainly to isolate the starchy endosperm rich in macronutrients as starch and storage proteins but thus lead to a loss of most of the healthy micronutrients, phytochemicals and fibres present in cereal grains. In comparison with wet fractionation, it presents the advantage of reducing effluents, avoiding post‐drying and additional energy cost. Depending on the processing steps, it is possible to control the tissue structure integrity and the enrichment of molecules with functional properties.

During the last years, a huge amount of data about the characterization and localization of compounds with nutritional interest have been obtained. Different strategies have been developed to limit the germ and aleurone removal or to reintroduce part of the bran and co‐fractions or isolated compounds of interest into the endosperm fractions in order to increase the nutritional value of the product. These new fractionation diagrams are now possible due to the development of rapid methods for characterization and identification of biochemical markers to monitor the tissue behavior during processing. However, introduction of bran or germ fractions in flour or semolina cannot only alter the technological properties of the final products (i.e., texture, volume, color, shelf‐life), but also their sensory properties and thus the general acceptability of the products. Depending on the tissue introduced it is also important to re‐evaluate the products’ safety. As an example, if the increase of heath beneficial component can be reach by substituting 10% of flour by de‐branning fractions enriched in the aleurone layer, this percentage could not be further increased without dramatically altering the technological properties of the bread, and accumulating the contaminating deoxynivalenol mycotoxin (Blandino et al. 2013).

If strategies exist to enrich cereal foods with compounds with nutritional interest, recent data have also noted that the limiting factor is not only the average amount of such compounds but also their accessibility. Therefore, recent studies have shown that physical (mechanical) or biological (enzymatical) pre‐treatment of the fractions used for enrichment (bran or aleurone layer) are efficient to increase the micronutrient accessibility.

The enrichment of a target compound in the final product depends on (a) the considered cereal, as differences in amount and location exists between distinct cereal grains; (b) its accumulation in grains, which relies on the genetic background of the chosen cultivar and the environmental conditions along growth; (c) the choice of fractionation steps, which impact the compound distribution in the fractions. The health potential will depend on the molecule bioavailability depending both on its chemical form and its interactions with other components in the food matrix. Consumer acceptance of the product finally depends on a number of parameters (sensory properties, price, convenience, etc.), which are strongly affected by socio‐economical and ethnical factors.

Therefore, future research has to select the most adapted cereal grains, cultivars and samples in relation with processing steps. However, to build both the best healthy cereal food and the most suitable for consumer acceptance, it has not only to optimize the first transformation but to consider the overall chain, from the field to the fork.