Vanesa Benítez

Characterization of Industrial Onion Wastes (Allium cepa L.): Dietary Fibre and Bioactive Compounds

The food industry produces a large amount of onion wastes, making it necessary to search for possible ways for their utilization. One way could be to use these onion wastes as a natural source of high-value functional ingredients, since onion are rich in several groups of compounds, which have perceived benefits to human health. The objective of this work is to gain knowledge of any differences between the different onion wastes obtained from industry and non-commercial bulbs to use them as food ingredients rich in specific compounds. The results showed that brown skin and top–bottom could be potentially used as functional ingredient rich in dietary fibre, mainly in insoluble fraction, and in total phenolics and flavonoids, with high antioxidant activity. Moreover, brown skin showed a high concentration of quercetin aglycone and calcium, and top–bottom showed high concentration of minerals. Outer scales could be used as source of flavonols, with good antioxidant activity and content of dietary fibre. However, inner scales could be an interesting source of fructans and alk(en)yl cystein sulphoxides. In addition, discarded onions (cvs Recas and Figueres) could be used as a good source of dietary fibre, and cv Recas also as a source of phenolics compounds.

Starch, Functional Properties, and Microstructural Characteristics in Chickpea and Lentil As Affected by Thermal Processing

Changes in starch, functional, and microstructural characteristics that occurred in chickpea and lentil under soaking, cooking, and industrial dehydration processing were evaluated. Available starch in raw legumes represented 57-64%, and resistant starch (RS) is a significant component. As a result of cooking, available starch contents of soaked chickpea and lentil were significantly increased (21 and 12%, respectively) and RS decreased (65 and 49%, respectively) compared to raw flours. A similar trend was exhibited by dehydration, being more relevant in lentil (73% of RS decrease). The minimum nitrogen solubility of raw flours was at pH 3, and a high degree of protein insolubilization (80%) was observed in dehydrated flours. The raw legume flours exhibited low oil-holding capacities, 0.95-1.10 mL/g, and did not show any change by thermal processing, whereas water-holding capacities rose to 4.80-4.90 mL/g of sample. Emulsifying activity and foam capacity exhibited reductions as a result of cooking and industrial dehydration processing. The microstructural observations were consistent with the chemical results. Thus, the obtained cooked and dehydrated legume flours could be considered as functional ingredients for food formulation.

Evaluation of Phenolic Profile and Antioxidant Properties of Pardina Lentil As Affected by Industrial Dehydration

This study presents the effects of soaking, cooking, and industrial dehydration treatments on phenolic profile and also on antioxidant properties in Pardina lentil. HPLC-PAC and HPLC-MS (ESI) analysis identified a total of 35 phenolic compounds in raw and processed lentil flours, corresponding to catechins and procyanidins (69% of the total of identified phenolic compounds), flavonols (17%), flavones, and flavanones (5%), and hydroxybenzoic and hydroxycinnamic compounds (5 and 4%, respectively). During the industrial process, catechins and procyanidins, flavonols, flavones, and flavanones decreased, while hydroxybenzoic compounds exhibited an important increase. In addition, raw lentils showed high values of the antioxidant activity (66.97 μmol Trolox/g); although the thermal processing promotes decreased, the levels of antioxidant activity were still relevant. Thus, the significant occurrence of bioactive phenolic compounds along with the interesting antioxidant capacity of dehydrated lentil flours make them useful for daily inclusion in the human diet as ready-to-use for special meals to specific populations.

Changes in nonnutritional factors and antioxidant activity during germination of nonconventional legumes

The present study describes the effects of germination on nonnutritional factors and antioxidant activity in the nonconventional legumes Vigna unguiculata (cowpea), Canavalia ensiformis (jack bean), Lablab purpureus (dolichos), and Stizolobium niveum (mucuna). Protease inhibitors and lectins were detected in raw legumes and were significantly decreased during the germination. Regarding total and individual inositol phosphates (IP5-IP3), important reductions of IP6 and high increases in the rest of inositol phosphates were also detected during this process. In addition, total phenols, catechins, and proanthocyanidins increased, accompanied by an overall rise of antioxidant activity (79.6 μmol of Trolox/g of DW in the case of mucuna). Germination has been shown to be a very effective process to reduce nonnutritional factors and increase bioactive phenolic compounds and antioxidant activities of these nonconventional legumes. For this reason, they could be used as ingredients to obtain high-value legume flours for food formulation.

Effect of sterilisation on dietary fibre and physicochemical properties of onion by-products

Food industries are forced to develop productions without secondary residues. Therefore, there is a considerable emphasis on the recovery, recycling and upgrading of wastes. The possibility has been suggested for the conversion of onion waste into food ingredients, but with a stabilisation treatment being necessary. The objective of this work was to study the effect of sterilisation on fibre fractions, fibre composition and physicochemical properties of onion by-products to evaluate the use of sterilised onion by-products as a source of fibre. Sterilisation produced insoluble dietary fibre decreases and soluble dietary fibre increases, improving the soluble:insoluble ratio. Uronic acids of insoluble dietary fibre were partly solubilised and losses of cellulose and Klason lignin were observed. Physicochemical properties slightly changed with sterilisation. Sterilised by-products showed less oil holding capacity, cation exchange capacity and swelling capacity than control ones, although their physicochemical properties were generally higher than those of cellulose. Therefore, sterilisation would be considered a good method to stabilise onion by-products to use as a potential dietary fibre ingredient.

Estimation of scavenging capacity of melatonin and other antioxidants: Contribution and evaluation in germinated seeds

Seven edible seeds for the levels of melatonin, phenolic compounds and their antioxidant capacity were evaluated during germination process. Radical scavenging parameters were also studied in standard antioxidants to understand their antiradical actions. Germination brought about significant increases of total phenol compounds in all edible seeds, showing red cabbage, radish and broccoli the highest contents (21.6, 20.4 and 16.4 mg GAE/g DW, respectively). The concentration of melatonin is greatly variable in edible seeds, exhibiting significant increases during germination. The highest levels were found in red cabbage (857 pg/g DW) radish (536 pg/g DW) and broccoli (439 pg/g DW). The germinated seeds which had the highest levels of polyphenols and melatonin were those that showed the most relevant antiradical activities (>97%). This information is valuable for the incorporation of red cabbage, radish and broccoli germinated seeds into the diet to promote potential health benefits.

Effect of Illumination on the Content of Melatonin, Phenolic Compounds, and Antioxidant Activity During Germination of Lentils (Lens culinaris L.) and Kidney Beans (Phaseolus vulgaris L.)

This study reports the effects of two different illumination conditions during germination (12 h light/12 h dark vs 24 h dark) in lentils (Lens culinaris L.) and kidney beans (Phaseolus vulgaris L.) on the content of melatonin and phenolic compounds, as well as the antioxidant activity. Germination led to relative increase in melatonin content and significant antioxidant activity, while the content of phenolic compounds decreased. The highest melatonin content was obtained after 6 days of germination under 24 h dark for both legumes. These germinated legume seeds with improved levels of melatonin might play a protective role against free radicals. Thus, considering the potent antioxidant activity of melatonin, these sprouts can be consumed as direct foods and be offered as preventive food strategies in combating chronic diseases through the diet.

Onion (Allium cepa L.) by-products as source of dietary fiber: physicochemical properties and effect on serum lipid levels in high-fat fed rats

The effect of industrial processes used to obtain onion by-products was evaluated. Fiber composition and physicochemical properties were assessed in order to choose the best process to obtain high-fiber ingredients. Moreover, the effect of the inclusion of the dietary fiber-rich onion by-products in a high-fat diet on serum lipids of rats was also evaluated. Bagasse was the best by-product since it showed the highest fiber content with a balanced soluble-to-insoluble fiber ratio and the best physicochemical properties. This fact is related to its high fiber content and also due to its composition, rich in uronic acids and polysaccharides, which explains its high cation exchange capacity, water-holding capacity and swelling capacity. In addition, the inclusion of Bagasse in a high-fat diet produced a reduction in the serum lipid and total cholesterol increases induced by high-fat diet. This effect could be related to the high cation exchange and swelling capacities that Bagasse showed, since these properties can create a concerted effect in reducing the number of intact micelles available, the transit time, and consequently the total time available for cholesterol and lipid absorption in the small intestine.

Melatonin Synthesis in Fermented Foods

Abstract Melatonin (MEL) is a natural powerful antioxidant that may provide beneficial human health effects. Given that MEL is absorbed when melatonin-containing foods are eaten, the intake of these foods could maintain plasma melatonin concentration, which diminishes with age. Fermentation increases the MEL levels in foods and is considered a promising technological process by different sectors (consumers, industry, etc.). The formation of MEL and its isomers (IMs) occurs during controlled alcoholic fermentation of different foods. This is due to the action of microorganisms (yeasts and bacteria) and environmental stressors as elevated alcohol levels or lactic-acid production may naturally increase in these bioactive compounds. The possible enhancement of MEL and IMs in the fermented foods could improve their health benefits by increasing their blood levels in humans, thereby improving antioxidative defense mechanisms.

Sources of Fiber

Dietary fiber (DF) is an important component of a healthy diet and is naturally present in plant foods. Depending on the source of fiber, the content, structure, chemical composition, physico-chemical properties, and physiological effects are different. Traditionally, most of the DF intake comes from the cell walls of vegetables, fruits, cereal products, and other seeds. However, in recent years food manufacturers have developed fiber-enriched foods using high-fiber ingredients, in order to increase the DF daily intake of the population due to the beneficial effects associated to fiber. Different plant foods have been reviewed in relation to their content and composition of DF. Moreover, we have included a review of the main changes of DF as a consequence of food processing. Furthermore, as the food market is constantly looking for new sources of healthy fibers to satisfy the growing consumer requests, agroindustrial by-products have been studied to evaluate their potential as high fiber ingredients.