Bioequivalence of β‐carotene and retinol

For many years it was accepted that 6 mg of β‐carotene were required to produce 1 mg of vitamin A in the form of retinol. The equivalence was based on the assumptions that two‐thirds of dietary β‐carotene are not absorbed, while in the metabolism of the remaining third 1 mol of β‐carotene is converted to 1 mol retinol. Recently, the bioequivalence was raised to 12 mg β‐carotene and 1 mg retinol. The objective of this review was to re‐examine the data that were used to support the new equivalence ratio, especially since some of these data were obtained in developing countries where infestation with gut parasites and exposure to other infections is common, yet the influence of inflammation on plasma carotenoid and retinol concentrations is frequently ignored. Bioequivalence studies examined in this review include those done in developing and developed countries, depletion and repletion studies, feeding with vegetable sources of β‐carotene or pure supplements, influence of helminths, carotenoid interactions and matrix effects and studies using stable isotopes (SI). SI studies show the bioefficacy of β‐carotene conversion to retinol is generally poor even for pure β‐carotene unless the dose is small and fed regularly until equilibration is reached. Retinol formation appears to be inversely influenced by previous vitamin A intake, the amount of material given and current vitamin A status. In spite of technical complexities, more SI studies where liver reserves of vitamin A are determined pre and post intervention are needed to evaluate β‐carotene bioefficacy of different vegetable sources. Copyright © 2006 Society of Chemical Industry     

Effect of polyglycerol esters of fatty acids on physicochemical properties and stability of β‐carotene nanodispersions prepared by emulsification/evaporation method

The effects of six different polyglycerol esters of fatty acids (PGEs) as nonionic emulsifiers on the physicochemical properties and stability of β‐carotene nanoparticles in oil‐in‐water dispersions produced by an emulsification/evaporation technique were examined. The β‐carotene particle size was measured by a laser diffraction technique, and the stability and retention of β‐carotene during various preparation steps and storage were determined by HPLC. In the prepared nanodispersions the β‐carotene particle size decreased with increasing degree of glycerol polymerisation and decreasing carbon number of the fatty acid group in the PGE. The particle size of β‐carotene in nanodispersions containing polyglycerol monooleate was generally larger than that in the presence of polyglycerol monolaurate. During storage at 4 °C, although the β‐carotene content in the nanodispersions showed a significant ( P < 0.05) decrease with increasing storage period, the size distribution of β‐carotene was almost unchanged in all prepared nanodispersions. In general, the mean diameter of β‐carotene nanoparticles ranged from 85 to 132 nm. In the light of their ability to physically stabilise β‐carotene particle formation, it is suggested that PGEs with a high degree of glycerol polymerisation may be useful in the preparation of β‐carotene nanodispersions. The best stabilisation was obtained using 10 g kg^?1 decaglycerol monolaurate. Copyright © 2004 Society of Chemical Industry     

Microencapsulation of β‐carotene using native pinhão starch,modified pinhão starch and gelatin by freeze‐drying

Beta‐carotene was microencapsulated by freeze‐drying using native pinhão starch, hydrolysed pinhão starch 6 dextrose equivalent (DE), hydrolysed pinhão starch 12 DE and the mixture of these materials with gelatin as coating material. The purpose of this research was to produce and characterize these microcapsules. The capsules’ efficiency, surface content, moisture, morphology, solubility, particle size and glass transition temperature were analysed. The hydrolysed pinhão starch 12 DE showed the highest total β‐carotene content and the lowest surface β‐carotene content, unlike the native starch. Using scanning electron microscopy, it was observed that all microcapsules presented undefined shapes. The samples with gelatin had wider particle size distribution, higher diameters, lower solubility and higher glass transition temperature when compared with other the samples. Results obtained suggest that the modified pinhão starch can be considered as potential wall material for encapsulation of β‐carotene.     

Tomatine,chlorophyll, β‐carotene and lycopene content in tomatoes during growth and maturation

Tomato (Lycopersicon esculentum) plants synthesise nutrients, pigments and secondary metabolites. These include the green pigment chlorophyll, the yellow pigment β‐carotene, the red pigment lycopene and the colourless glycoalkaloid α‐tomatine. The levels of these compounds are strongly influenced by the maturity of the tomatoes. Widely consumed Japanese tomato varieties Momotaro, Momotaro‐T93 and First Memory at five different stages of ripeness, each harvested at 10, 20, 30, 40 and 50 days after flowering of the plants, were analysed for the contents of these compounds. Additionally, tomato clusters from different locations along the vine on the same plant were also evaluated. The results show that chlorophyll and tomatine concentrations decrease rapidly during the growth of the tomatoes. By contrast, β‐carotene and lycopene levels are low in immature and high in mature tomatoes. The location of the tomato clusters and tomato variety did not significantly affect these results. The possible usefulness of these results to optimise health‐promoting effects of tomatoes is discussed. © 2003 Society of Chemical Industry     

Enhanced bioaccessibility of β‐carotene from yellow‐orange vegetables and green leafy vegetables by domestic heat processing

Effect of heat treatment involved in domestic cooking on the bioaccessibility of β‐carotene from yellow‐orange as well as green leafy vegetables was evaluated. Heat treatment of these vegetables by pressure‐cooking, stir‐frying and open‐pan boiling had a beneficial influence on the bioaccessibility of β‐carotene. The extent of increase in the per cent bioaccessibility of β‐carotene as a result of pressure‐cooking was 21–84%. Stir‐frying in presence of a small quantity of oil brought about an enormous increase in the bioaccessibility of β‐carotene from these vegetables, the extent of increase being 67–191%. Open‐pan boiling of vegetables increased the bioaccessibility of β‐carotene in the range 23–36%. Thus, among the three domestic heat processing methods, stir‐frying results in maximum bioaccessibility of this provitamin. The use of suitably heat‐processed vegetable sources of β‐carotene could form a dietary strategy to derive this micronutrient maximally by the population dependent on plant foods.     

A proposed mechanism for the inhibition of soybean lipoxygenase by β‐carotene

The inhibition mechanism of soybean lipoxygenase (LOX) by β‐carotene was studied. Addition of β‐carotene into the reaction mixture decreased the rate of conjugated diene formation. Increasing the concentration of β‐carotene in the reaction mixture resulted in a decrease in the rate of conjugated diene formation. Although the rate of conjugated diene formation was lower in the presence of β‐carotene, the same amounts of linoleic acid hydroperoxides were formed by the enzyme at the end of the reaction, both with and without β‐carotene in the reaction medium. The rates of conjugated diene formation for 40, 20, 10 and 4 U mL^?1 LOX enzyme were almost equal to zero when the concentrations of β‐carotene were 20, 17.5, 15 and 10 µmol L^?1 in model reaction systems, respectively. β‐Carotene directly influences the amount of enzyme in the reaction medium available for the catalytic conversion of linoleic acid into corresponding hydroperoxides. The results obtained here suggest that β‐carotene reacts with linoleyl radical (L^?) at the beginning of the chain reaction, preventing the accumulation of conjugated diene forms (LOO^?, LOO^? and LOOH). Since L^? transforms back to its original form of LH, the enzyme cannot complete the chain reaction and thus remains at inactive Fe(II) form. Copyright © 2005 Society of Chemical Industry     

Effect of Lipid Physical State of Palm Derivatives on β‐Carotene Bleaching

This research was addressed to study the effect of lipid physical state on bleaching kinetics of β‐carotene. To this aim, β‐carotene was added to palm oil and palm stearin and the samples were stored at increasing temperatures allowing different degree of crystallization. Phase transition properties of palm derivatives were studied by differential scanning calorimetry and synchrotron X‐ray diffraction, whereas β‐carotene bleaching kinetics were followed by measuring color changes. Bleaching proceeded at comparable rate in palm oil and palm stearin containing systems stored at 20 and ?18 °C, whereas the color changes showed a maximum rate at 4 °C in palm stearin samples and at ?7 °C in palm oil systems. Arrhenius plot clearly highlighted deviations from the linearity underlining the crucial role of lipid physical properties in determining the bleaching rate. The location and the compartmentalization of β‐carotene in the fat lattice could affect its chemical stability.     

2‐Furoylmethyl amino acids,hydroxymethylfurfural, carbohydrates and β‐carotene as quality markers of dehydrated carrots

BACKGROUND: Processing of vegetables in the food industry usually includes dehydration as a preservation process. Industrial convective air drying of carrot can involve steam blanching of the raw product after peeling and cutting, and different stages of dehydration (first space, second space and final drying). Although the shelf‐life of carrot is significantly extended, important changes in its chemical composition can take place during dehydration since high temperatures and long times are used. This research is a preliminary study to evaluate the usefulness of β‐carotene, carbohydrates, hydroxymethylfurfural (HMF) and 2‐furoylmethyl amino acids (2‐FM‐AA) as quality markers of dehydrated carrots. RESULTS: A considerable decrease in β‐carotene and reducing carbohydrates was observed during dehydration. HMF, absent in raw carrots, increased during the whole drying process and the highest formation was found during the steam blanching stage. 2‐FM‐AA of lysine, arginine, γ‐aminobutyric acid and alanine were progressively originated up to the second space and decreased during the final drying. CONCLUSION: The combined use of HMF and 2‐FM‐AA seems to be advantageous for the assessment of the optimal processing conditions to obtain high‐quality dehydrated carrots. Copyright © 2008 Society of Chemical Industry     

Screening of β‐Glucosidase and β‐Xylosidase Activities in Four Non‐Saccharomyces Yeast Isolates

The finding of new isolates of non‐Saccharomyces yeasts, showing beneficial enzymes (such as β‐glucosidase and β‐xylosidase), can contribute to the production of quality wines. In a selection and characterization program, we have studied 114 isolates of non‐Saccharomyces yeasts. Four isolates were selected because of their both high β‐glucosidase and β‐xylosidase activities. The ribosomal D1/D2 regions were sequenced to identify them as Pichia membranifaciens Pm7, Hanseniaspora vineae Hv3, H. uvarum Hu8, and Wickerhamomyces anomalus Wa1. The induction process was optimized to be carried on YNB‐medium supplemented with 4% xylan, inoculated with 106 cfu/mL and incubated 48 h at 28 °C without agitation. Most of the strains had a pH optimum of 5.0 to 6.0 for both the β‐glucosidase and β‐xylosidase activities. The effect of sugars was different for each isolate and activity. Each isolate showed a characteristic set of inhibition, enhancement or null effect for β‐glucosidase and β‐xylosidase. The volatile compounds liberated from wine incubated with each of the 4 yeasts were also studied, showing an overall terpene increase (1.1 to 1.3‐folds) when wines were treated with non‐Saccharomyces isolates. In detail, terpineol, 4‐vinyl‐phenol and 2‐methoxy‐4‐vinylphenol increased after the addition of Hanseniaspora isolates. Wines treated with Hanseniaspora, Wickerhamomyces, or Pichia produced more 2‐phenyl ethanol than those inoculated with other yeasts.     

Porosity and Water Activity Effects on Stability of Crystalline β‐Carotene in Freeze‐Dried Solids

Abstract: Stability of entrapped crystalline β‐carotene as affected by water activity, solids microstructure, and composition of freeze‐dried systems was investigated. Aliquots (1000 mm³, 20% w/w solids) of solutions of maltodextrins of various dextrose equivalents (M040: DE6, M100: DE11, and M250: DE25.5), M100‐sugars (1:1 glucose, fructose and sucrose), and agar for gelation with dispersed β‐carotene were frozen at ?20, ?40, or ?80 °C and freeze‐dried. Glass transition and α‐relaxation temperatures were determined with differential scanning calorimetry and dynamic mechanical analysis, respectively. β‐Carotene contents were monitored spectrophotometrically. In the glassy solids, pore microstructure had a major effect on β‐carotene stability. Small pores with thin walls and large surface area allowed β‐carotene exposure to oxygen which led to a higher loss, whereas structural collapse enhanced stability of β‐carotene by decreasing exposure to oxygen. As water plasticized matrices, an increase in molecular mobility in the matrix enhanced β‐carotene degradation. Stability of dispersed β‐carotene was highest at around 0.2 a_w, but decreasing structural relaxation times above the glass transition correlated well with the rate of β‐carotene degradation at higher a_w. Microstructure, a_w, and component mobility are important factors in the control of stability of β‐carotene in freeze‐dried solids Practical Application: β‐Carotene expresses various nutritional benefits; however, it is sensitive to oxygen and the degradation contributes to loss of nutritional values as well as product color. To increase stability of β‐carotene in freeze‐dried foods, the amount of oxygen penetration need to be limited. The modification of freeze‐dried food structures, for example, porosity and structural collapse, components, and humidity effectively enhance the stability of dispersed β‐carotene in freeze‐dried solids.     

Fatty acids and all‐trans‐β‐carotene are correlated in differently colored rice landraces

A set of 54 rice landrace samples was compiled from various Asian countries, including six red/brownish and eight black/purple varieties. Brown rice samples were analyzed for lipid content and fatty acid profile, as well as all‐trans‐β‐carotene content. Black/purple varieties were found to be higher in crude lipid content than the red/brownish and colorless varieties. They also had a higher β‐carotene content than the other two color classes. The highest β‐carotene content determined was 0.22 mg kg⁻¹. Black/purple varieties tended to have a higher proportion of saturated fatty acids in their lipid fraction and a lower proportion of unsaturated fatty acids. The differences were statistically significant (P < 0.05) for oleic acid, which accounted for 42.1% of the lipid fraction in black/purple varieties and for 45.3% and 46.3% in red/brownish and colorless varieties, respectively. β‐Carotene content showed a significantly positive correlation with the crude lipid content (P < 0.001) and the content of saturated fatty acids (P < 0.001) on a dry matter basis. However, it was not correlated with the unsaturated fatty acids content on a dry matter basis. Within the total lipid extract, β‐carotene showed a significantly positive correlation with the proportion of saturated fatty acids (P < 0.01), especially palmitic acid (P < 0.01), and a significantly negative correlation with unsaturated fatty acids (P < 0.001), especially oleic acid (P < 0.01). Copyright © 2005 Society of Chemical Industry     

In vitro bioaccessibility of β‐carotene in dried carrots pretreated by different methods

The effects of selected pretreatment methods, i.e. soaking in citric acid, blanching in water and blanching in citric acid, as well as hot‐air drying (at 70, 80 and 90 °C), on the retention and relative in vitro bioaccessibility of β‐carotene in dried carrots were investigated. The results indicated that the selected pretreatments and drying could enhance the relative bioaccessibility of β‐carotene in dried carrots. The relative bioaccessibility of β‐carotene in dried carrots increased to 47–73%, while the values in the fresh (13%) and dried untreated (31–47%) carrots were lower. Although significant losses of β‐carotene occurred during both the pretreatment and drying processes, bioaccessible β‐carotene contents of dried pretreated carrots were in a similar order to those of the fresh carrots, indicating the ability and hence the benefit of appropriate pretreatment and drying processes in maintaining the nutritive quality of a food product.     

Effects of microwave and hot‐air drying methods on colour, β‐carotene and radical scavenging activity of apricots

The effects of drying by microwave and convective heating at 60 and 70 °C on colour change, degradation of β‐carotene and the 2,2‐diphenyl‐1‐picrylhydrazyl radical (DPPH) scavenging activity of apricots were evaluated. Microwave heating reduced significantly the drying time (up to 25%), if compared with convective one, also owing to the higher temperature reached during the last phase of the process, as monitored by infrared thermography. Colour changes of apricot surface, described with lightness and hue angle, in both drying methods followed a first‐order reaction (0.927 ≤ R² ≤ 0.996). The apricots dried by microwave were less affected by the darkening phenomena. The evolution of β‐carotene in fresh apricots (61.2 ± 5.6 mg kg^?1 d.w.) during the drying highlighted a wider decrease (about 50%) when microwave heating was employed for both the temperatures used. Radical scavenging activity increased (P < 0.05) in all dried samples except for hot‐air dried apricots at 60 °C.     

Purification and physicochemical characterization of ovine β‐lactoglobulin and α‐lactalbumin

Ovine whey proteins were fractionated and studied by using different analytical techniques. Anion‐exchange chromatography and reversed‐phase high‐performance liquid chromatography (HPLC) showed the presence of two fractions of β‐lactoglobulin but only one of α‐lactalbumin. Gel permeation and sodium dodecyl sulfate (SDS)‐polyacrylamide gel electrophoresis allowed the calculation of the apparent molecular mass of each component, while HPLC coupled to electrospray ionisation‐mass spectrometry (ESI‐MS) technique, giving the exact molecular masses, demonstrated the presence of two variants A and B of ovine β‐lactoglobulin. Amino acid compositions of the two variants of β‐lactoglobulin differed only in their His and Tyr contents. Circular dichroism spectroscopy profiles showed pH conformation changes of each component. The thermograms of the different whey protein components showed a higher heat resistance of β‐lactoglobulin A compared to β‐lactoglobulin B at pH 2, and indicated high instability of ovine α‐lactalbumin at this pH.     

Thermal modifications of structure and codenaturation of α‐lactalbumin and β‐lactoglobulin induce changes of solubility and susceptibility to proteases

Study of heat denaturation of major whey proteins (β‐lactoglobulin or α‐lactalbumin) either in separated purified forms, or in forms present in fresh industrial whey or in recomposed mixture respecting whey proportions, indicated significant differences in their denaturation depending on pH, temperature of heating, presence or absence of other co‐denaturation partner, and of existence of a previous thermal pretreatment (industrial whey). α‐Lactalbumin, usually resistant to tryptic hydrolysis, aggregated after heating at ⪈85°C. After its denaturation, α‐lactalbumin was susceptible to tryptic hydrolysis probably because of exposure of its previously hidden tryptic cleavage sites (Lys‐X and Arg‐X bonds). Heating over 85°C of β‐lactoglobulin increased its aggregation and exposure of its peptic cleavage sites. The co‐denaturation of α‐lactalbumin with β‐lactoglobulin increased their aggregation and resulted in complete exposure of β‐lactoglobulin peptic cleavage sites and partial unveiling of α‐lactalbumin tryptic cleavage sites. The exposure of α‐lactalbumin tryptic cleavage sites was slightly enhanced when the α‐lactalbumin/β‐lactoglobulin mixture was heated at pH 7.5. Co‐denaturation of fresh whey by heating at 95°C and pH 4.5 and above produced aggregates stabilized mostly by covalent disulfide bonds easily reduced by β‐mercaptoethanol. The aggregates stabilized by covalent bonds other than disulfide arose from a same thermal treatment but performed at pH 3.5. Thermal treatment of whey at pH 7.5 considerably enhanced tryptic and peptic hydrolysis of both major proteins.     

Constitutive Effects of Lead on Aryl Hydrocarbon Receptor Gene Battery and Protection by β‐carotene and Ascorbic Acid in Human HepG2 Cells

Lead (Pb) is an environmental pollutant that can get entry into human body through contaminated foods, drinks, and inhaled air leading to severe biological consequences, and has been responsible for many deaths worldwide. The objectives of this study were 1st to investigate the modulatory effects of environmentally relevant concentrations of Pb on AhR gene battery, which is controlling xenobiotics metabolism. 2nd, trials to reduce Pb‐induced adverse effects were done using some phytochemicals like β‐carotene or ascorbic acid. Human hepatoma (HepG2) cell lines were exposed to a wide range of Pb concentrations varying from physiological to toxic levels (0 to 10 mg/L) for 24 h. High Pb concentrations (1 to 10 mg/L) significantly reduced phase I (CYP1A1 and 1A2) and phase II (UGT1A6 and NQO1) xenobiotic metabolizing enzyme mRNA expression in a mechanistic manner through the AhR regulation pathway. Additionally, these Pb concentrations induced oxidative stress in HepG2 cells in terms of production of reactive oxygen species (ROS) and induced heme oxygenase‐1 mRNA expression in a concentration‐dependent phenomenon. Coexposure of HepG2 cells to physiological concentrations of some micronutrients, like β‐carotene (10 μM) or ascorbic acid (0.1 mM), along with Pb (1 mg/L) for 24 h significantly reduced the levels of ROS production and recovered AhR mRNA expression into the normal levels. Thus, consumption of foods rich in these micronutrients may help to reduce the adverse effects of lead in areas with high levels of pollution.     

Degradation of Lycopene and β‐carotene in Model Systems and in Lyophilized Guava during Ambient Storage: Kinetics,Structure, and Matrix Effects

ABSTRACT: Being highly unsaturated, carotenoids are susceptible to isomerization and oxidation during the processing and storage of food. In the present study, the degradation of acyclic lycopene and dicyclic β‐carotene in low‐moisture and aqueous model systems, as well as in lyophilized guava, during storage at ambient temperature, in the absence or presence of light, was investigated. Both carotenoids followed first order kinetics under the various conditions investigated. Lycopene degraded much faster than β‐carotene in all the model systems. In a comparison of lycopene isolated from guava, tomato, and watermelon, greater losses were observed with lycopene from tomato. Since the model system was identical in the 3 cases, these results indicated that other compounds from the food sources, co‐extracted with lycopene, might have influenced the oxidation. Light consistently and strongly promoted degradation under all conditions studied. The susceptibility of lycopene to degradation was much less in lyophilized guava than in the model systems, showing the marked protective influence of the food matrix. Loss of β‐carotene, found at a concentration of about 18 times lower than lycopene, was only slightly lower than that of lycopene in lyophilized guava, indicating that the effect of matrix and/or the initial concentration overshadowed the structural influence.     

Changes in the carotenoid content of apricot (Prunus armeniaca,var Bergeron) during enzymatic browning: β‐carotene inhibition of chlorogenic acid degradation

Considering the numerous beneficial effects in human health ascribed to carotenoids, studies were performed to investigate the modification of carotenoid amount and composition during apricot enzymatic browning. First works on bruised apricot purees have shown a trans‐β‐carotene isomerisation (20%) induced by enzymatic browning. To clarify this isomerisation, oxidation of chlorogenic acid in presence of trans‐β‐carotene, catalysed by purified apricot polyphenoloxidase (PPO), was followed by HPLC and polarography. Isomerisation rate of trans‐β‐carotene in its cis isomer was found to increase with chlorogenic acid concentration. Moreover, trans‐β‐carotene was shown to be a potent inhibitor of phenol degradation. This inhibition was partially ascribed to PPO inhibition (non‐competitive inhibitor towards phenol with an apparent Ki close to 0.5 mM , a mixed type inhibitor towards oxygen with an apparent Ki close to 0.15 mM ). The additional inhibition was explained by non‐enzymatic reactions involving trans‐β‐carotene and chlorogenic acid o‐quinones and leading to phenol regeneration and carotene isomerisation. © 2000 Society of Chemical Industry