High dietary fibre powders from orange and lime peels: associated polyphenols and antioxidant capacity

High dietary fibre powders from Valencia orange and Persa lime peels were prepared and their dietary fibre composition and antioxidant capacity studied. Fibres from both peels had a high total dietary fibre content (61–69%) with an appreciable amount of soluble fibre (19–22%). The concentration of antioxidant [AA₅₀] required to achieve a 50% inhibition of oxidation of linoleic acid at 40°C was measured using the ferric-thiocyanate method. The higher the [AA₅₀], the lower the antioxidant capacity. Lime peel fibre [AA₅₀] was half the value of DL--tocopherol and 23 times lower than orange peel fibre; the [AA₅₀] of commercial butylated hydroxyanisole (BHA) was half the value of lime fibre. HPLC analyses of the polyphenols extracted from orange and lime peels fibres showed the presence of caffeic and ferulic acids, as well as naringin, hesperidin and myricetin in both fruit fibres. The different antioxidant power of these fibres could be in part explained by the presence in lime peel fibre of ellagic acid, quercetin and kaempferol which are strong antioxidant polyphenols.     

Bioactive compounds and antioxidant capacities of 18 non-traditional tropical fruits from Brazil

The bioactive compounds and antioxidant capacities of polyphenolic extracts of 18 fresh and dry native non-traditional fruits from Brazil were determined using ABTS, DDPH, FRAP and β-carotene bleaching methods. The study provides an adaptation of these methods, along with an evaluation of the compounds related to antioxidant potential. The results show promising perspectives for the exploitation of non-traditional tropical fruit species with considerable levels of nutrients and antioxidant capacity. Although evaluation methods and results reported have not yet been sufficiently standardised, making comparisons difficult, our data add valuable information to current knowledge of the nutritional properties of tropical fruits, such as the considerable antioxidant capacity found for acerola – Malpighia emarginata and camu-camu – Myrciaria dubia (ABTS, DPPH and FRAP) and for puçá-preto – Mouriri pusa (all methods).     

Evaluation of CIE-lab colour parameters during the clarification of a sugar syrup from Mesquite pods (Prosopis Pallida L.)

Summary There are several commercial sugar syrups obtained from the Mesquite pods, however their dark-brown colour limits their use in the food industry. In this work we clarified sugar syrups from Mesquite pods by a two-step procedure: (1) lime-milk treatment with the addition of different amounts of calcium hydroxide and aluminium sulphate, and (2) ion-exchange treatment using A-400 anionic and/or C-100 cationic resins. Samples were evaluated for colour using the Hunter Lab colorimeter (Hunter Associates Laboratory Inc, Reston, VA, USA) (L*, a*, b*, ) and for sensory acceptability during the clarification process. The results showed that with the addition of 7.5% calcium hydroxide and 8.0% aluminium sulphate, followed by treatment with the anionic resin A-400, a syrup with a high degree of purity (92.3%) and a lighter-brown colour than other commercial samples could be obtained. The colour values, as measured by the Hunter meter were; a lightness of L* = 6.17 and a yellow colour of 0.74 expressed as a a/b* ratio. A negative correlation was obtained between the total polyphenol content (TP) in the sugar extract and the lightness values (L*); L* = 15.50–0.00511 TP (mg kg^–1). The A-400 resin retained the greatest amount of polyphenols (92.9%). CIE-Lab parameters are proposed as a good means for objective colour comparison with other studies on the clarification of sugar syrups.     

Antioxidant capacity of the Spanish Mediterranean diet

The objective of this work was to determine the total dietary antioxidant capacity (TDAC) of the Spanish Mediterranean diet. The antioxidant capacity of plant foods and beverages included in National food consumption data was determined. TDAC of the Spanish diet was estimated at 6014 and 3549 μmol trolox equivalents by FRAP (ferric reducing antioxidant power) and ABTS (free radical-scavenging capacity) procedures, respectively. About 68% of TDAC came from beverages and 20% from fruits and vegetables, with a very low contribution from cereals. The capacity to inhibit in vitro LDL oxidation of plant foods and beverages was consistent with their antioxidant capacity. The recommended daily intakes of antioxidant vitamins, C and E, represent about 10% of TDAC. Total phenolics intake was estimated as 1171 mg gallic acid/person/day by the Folin–Ciocalteau method. TDAC may be a parameter to be considered in nutritional and epidemiological studies.     

Towards an updated methodology for measurement of dietary fiber,including associated polyphenols,in food and beverages

The analytical dietary fiber (DF) methods most widely used today were developed to determine non-starch polysaccharides and lignin. Updated dietary fiber definition includes all indigestible plant food constituents. Recent methods have proposed the measurement of resistant starch and oligosaccharides, but other major indigestible constituents such as polyphenolic compounds and resistant protein are still omitted in dietary fiber analysis. There is scientific evidence that an appreciable amount of dietary polyphenols are associated with the dietary fiber matrix, being a fermentable substrate for bacterial microflora. The objective of this work was to show polyphenols compounds are major constituents of dietary fiber and to propose a procedure for their measurement. Results showed that polyphenols are major constituents of DF, accounting from 1.4% to 50.7% (dry weight) of insoluble dietary fiber in plant foods and from 2.9% to 62.8% of soluble dietary fiber in common beverages.     

Proanthocyanidin content in foods is largely underestimated in the literature data: An approach to quantification of the missing proanthocyanidins

The content of proanthocyanidins (PA) in foods is usually determined by HPLC analysis of aqueous-organic extracts. However, the appreciable amounts of PA that remain in the residues of extraction usually are not considered for analysis. Attempts to determine these non-extractable proanthocyanidins (NEPA) by enzymatic-chemical methods have obtained partial results. The general aim of this work was the estimation of the total content of PA, including both extractable PA (EPA) and NEPA in some foods included in the USDA database. A specific procedure based on depolymerization by HCl/BuOH treatment was used to quantify NEPA. The content of NEPA in analyzed samples ranged from 11 mg/100 g for pear to 6.7 g/100 g dry weight for red grape pomace. The results showed that literature data underestimate the actual content of PA in foods. NEPA may have a significant contribution to the healthy effects associated to PA-rich foods and diets.     

Mineral composition of almond varieties (prunus amygdalus)

Summary The contents of all elements considered essential for plants were determined on seven Mediterranean almond varieties. Atomic absorption, colorimetry, turbidimetry and ion selective electrode procedures were used. The average contents of macronutrients and micronutrients in the almond were determined to be 1957 and 23.2 mg/100 g respectively. Rectilinear relationships between P and Ca, Cl and Na and N and Cu were found.

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Mineralstoffzusammensetzung verschiedener Mandelarten (Prunus amygdalus)

Zusammenfassung Der Gehalt aller wesentlichen Elemente wurde in sieben Mandelarten des Mittelmeergebietes bestimmt. Hierfür wurden die analytischen Methoden der Atomabsorption, der Colorimetrie, der Trübungsmessung und selektive Elektrodenverfahren verwendet. Die durchschnittlichen Gehalte der Makrobzw. Mikronährstoffe sind 1957 bzw. 23,2 mg/100 g Mandel. Lineare Beziehungen wurden bei den Gehalten von P and Ca, Cl and Na bzw. N und Cu gefunden.

     

Effects of dietary fibre‐ and polyphenol‐rich grape products on lipidaemia and nutritional parameters in rats

The aim of this work was to evaluate the effects of three dietary fibre‐ and polyphenol‐rich materials obtained from grapes on serum cholesterol, lipoprotein and triglyceride concentrations as well as on body weight, fat and protein digestibility in adult Wistar rats fed on cholesterol‐free and 10 g kg⁻¹ cholesterol‐added diets. Dietary fibre content of materials ranged from 540 to 590 g kg⁻¹. Intake of grape products increased stool weight and the amount of fat and protein excreted in faeces, but did not affect negatively animal growth or protein efficiency of the diet in Wistar rats. Studied grape fractions lower serum total cholesterol and LDL cholesterol concentrations in hypercholesterolemic rats. These results could be taken into account in potential applications of these products as a food ingredient. © 2000 Society of Chemical Industry     

Evaluation of free radical scavenging of dietary carotenoids by the stable radical 2,2‐diphenyl‐1‐picrylhydrazyl

In order to avoid the interference of compounds with a chromophoric system when the 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH^·) method is used, a new measure of the decrease in absorbance at 580 nm was performed (correlation coefficient between absorbance and DPPH^· concentration, 0.9979; p < 0.01). The antioxidant effectiveness of dietary carotenes and xanthophylls towards the stable free radical DPPH^· was measured. The antioxidant activity expressed as the amount of antioxidant able to reduce the initial DPPH^· concentration to 50% (EC₅₀), given in terms of moles of antioxidant per mole of DPPH^·, ranged from 0.16 ± 0.01 (lycopene) to 3.29 ± 0.31 (lutein). The parameter antiradical efficiency (AE), which involves the potency (1/EC₅₀) and the time taken to reach the steady state at EC₅₀ (T_EC50), was calculated to discriminate carotenoids with no significant difference between their EC₅₀. Comparison of the structures of the carotenoids tested revealed that the scavenging ability towards DPPH^· was increased by the length of the effective conjugated double‐bond system and was modulated by the addition of chemical groups on the terminal rings (xanthophylls). © 2000 Society of Chemical Industry