Why proanthocyanidins elute at increasing order of molecular masses when analysed by normal phase high performance liquid chromatography? Considerations of use.

Although it is widely known that proanthocyanidins elute at an increasing order of molecular masses when analysed by normal phase high performance liquid chromatography (NP-HPLC), there is no a consistent explanation of the mechanisms of their separation until now. Therefore, the aim of the present study was to give a reliable response to this question, using a complex procyanidin-rich grape seed extract. For this, an off-column static simulation of extract injection and a fragmented-column dynamic procyanidin location tests were studied to show their precipitation in an aprotic solvent, besides another off-column static simulation and multiple contact dynamic solubilisation tests to confirm procyanidin redissolution in an aprotic/protic solvent system. The results showed that separation of procyanidins in the aprotic/protic solvent system of Diol-NP-HPLC was governed by precipitation/redissolution mechanism, that could be extended to all known plant proanthocyanidin homopolymers, including hydrolysable tannins, if they are able to accomplish this condition. However, separation of monomer species, namely catechins and some hydroxybenzoic acids, was based on classic adsorption/partition mechanism. Other factors, such as analyte solubility, chromatographic conditions and sample preparation, that affect the viability of proanthocyanidin analysis by NP-HPLC were stand out and guidelines for its durable and reproducible use were defined.

Influence of dehydration process in Castellano chickpea: changes in bioactive carbohydrates and functional properties.

Changes in bioactive carbohydrates, functional, and microstructural characteristics that occurred in chickpea under soaking, cooking, and industrial dehydration processing were evaluated. Raw chickpea exhibited important levels of raffinose family of oligosaccharides (RFOs), resistant starch (RS) and total dietary fibre (TDF), being insoluble dietary fibre (IDF) the main fraction (94%). The dehydration process increased RFOs (43%), RS (47%) and soluble dietary fiber (SDF) (59%) levels significantly. In addition, a noticeable increase in both fibre fractions was observed, being higher in soluble fibre in (SDF) (59%). The minimum nitrogen solubility of raw flours was at pH 4, and a high degree of protein insolubilization (80%) was observed in dehydrated flours. The raw and processed flours exhibited low oil-holding capacities (1.10 mg/ml), and did not show any change by thermal processing, whereas water-holding capacities rose to 5.50 mg/ml of sample. Cooking and industrial dehydration process reduced emulsifying activity and foaming capacity of chickpea flour. The microstructural observations were consistent with the chemical results. Thus, the significant occurrence of these bioactive carbohydrate compounds along with the interesting functional properties of the dehydrated flours could be considered useful as functional ingredients for food formulation.

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.

Effect of industrial dehydration on the soluble carbohydrates and dietary fiber fractions in legumes.

The effects of soaking, cooking, and industrial dehydration treatments on soluble carbohydrates, including raffinose family oligosaccharides (RFOs), and also on total dietary fiber (TDF), insoluble dietary fiber (IDF), and soluble (SDF) dietary fiber fractions were studied in legumes (lentil and chickpea). Ciceritol and stachyose were the main alpha-galactosides for chickpea and lentil, respectively. The processing involved a drastic reduction of soluble carbohydrates of these legumes, 85% in the case of lentil and 57% in the case of chickpea. The processed legume flours presented low residual levels of alpha-galactosides, which are advisable for people with digestive problems. Processing of legumes involved changes in dietary fiber fractions. A general increase of IDF (27-36%) due to the increase of glucose and Klason lignin was observed. However, a different behavior of SDF was exhibited during thermal dehydration, this fraction increasing in the case of chickpea (32%) and decreasing in the case of lentil (27%). This is probably caused by the different structures and compositions of the cell wall networks of the legumes.

Effect of germination on the carbohydrate composition of the dietary fiber of peas (Pisum sativum L.).

The effect of different conditions of pea germination on dietary fiber (DF) composition was studied. Insoluble dietary fiber (IDF) and soluble dietary fiber (SDF) were subjected to acid hydrolysis, and the resultant neutral sugars, uronic acids, and Klason lignin were quantified. Germinated peas exhibited significantly higher contents of total dietary fiber (TDF) than the raw sample, due to the increases of both DF fractions. Under darkness conditions, germination exhibited the highest contents of IDF and SDF. Decreasing IDF/SDF ratios showed that the carbohydrate changes did not take place to the same extent during germination, the SDF fraction being the most affected. The detailed chemical composition of fiber fractions reveals increases of cellulose in the IDF of germinated samples, whereas SDF exhibits a decrease of pectic polysaccharides and also increases of polysaccharides rich in glucose and mannose. The DF results were corroborated by a comparative examination of the cell wall carbohydrate composition.

Effect of fermentation and autoclaving on dietary fiber fractions and antinutritional factors of beans (Phaseolus vulgaris L.).

The effect of fermentation on antinutritional factors and also on total dietary fiber (TDF), insoluble (IDF) and soluble (SDF) dietary fiber fractions was studied in beans (Phaseolus vulgaris L.). The processes studied were two types of fermentation (lactic acid and natural), and a portion of the obtained flours were processed by autoclaving. The dietary fiber (DF) content and its components were determined using the enzymatic-gravimetric and enzymatic-chemical methods. The TDF content ranged from 24.5% dry matter (DM) in the raw to 25.2% DM in the processed beans. All the processing treatments significantly decreased the SDF content, and irrelevant changes were noticed in the IDF content of processed beans. Cellulose content of all samples was reduced by the processing treatments. Correspondingly, higher amounts of resistant starch was observed in the processed beans, except in the lactic acid fermented ones. However, the levels of pectic polysaccharides and Klason lignin were higher in the samples fermented by Lactobacillus plantarum. The action of microorganisms was determinant for the different degradation of the bean cell wall, disrupting the protein-carbohydrate integration, thus reducing the solubility of DF.

Structural carbohydrate differences and potential source of dietary fiber of onion (Allium cepa L.) tissues.

Onion tissues of three varieties were evaluated for dietary fiber (DF) composition. Insoluble (IDF) and soluble (SDF) dietary fibers were subjected to acid hydrolysis, and the resultant neutral sugars, uronic acids, and Klason lignin were quantified. Brown skin exhibited the highest total dietary fiber (TDF) content (65.8%) on a dry matter basis, followed by top (48.5%) and bottom (38.6%), IDF being the main fraction found. The SDF:IDF ratio decreased from inner to outer tissues. Brown skin and outer leaves byproducts appear to be the most suitable sources of DF that might be used in food product supplementation. The chemical composition reveals that cellulose and pectic polysaccharides were the main components of onion DF in all tissues, although differences between them were noticed. An increase in the uronic acids/neutral sugars ratio from inner to outer tissues was found, suggesting that the galactan side chain shows a DF solubilization role.

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.

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.