Colorimetric Analysis of Hibiscus Beverages and their Potential Antioxidant Properties.

In food industry, roselle beverages and their subproducts could be functional ingredients since they are an excellent source of bioactive compounds with improved performance due to their important anthocyanins content. The aim of this study was to analyze anthocyanin content and antioxidant properties of aqueous infusions elaborated with color contrasting Hibiscus materials and design a mathematical model in order to predict color-composition relationship. Color measurements of beverages from roselle (Negra, Sudan and Rosa) were made by transmission spectrophotometry, anthocyanins quantification was determined by HPLC, and antioxidant potential was evaluated by in vitro methods (ABTS and FRAP assays). Beverages prepared with particle size minor of 250 µm presented until 4- and 2- times more anthocyanins content and antioxidant capacity respectively, in comparison to beverages prepared with powders with particle size major of 750 µm. Positive correlations among pigments composition and color parameters were found (p < 0.05), showing that anthocyanins content, antioxidant capacity, C*ab and hab values increased in relation with the smallest particle size of flours. Also, mathematical models were stablished to predict anthocyanin content (r ≥ 0.97) and antioxidant capacity (r ≥ 0.89) from color data; we propose equations for quick estimation of the antioxidant capacity in the Hibiscus beverages with high anthocyanin content. The obtained models could be an important tool to be used in food industry for pigment characterization or functional compounds with potential health benefits.

Comparative study of anthocyanin and volatile compounds content of four varieties of Mexican roselle (Hibiscus sabdariffa L.) by multivariable analysis.

Anthocyanins are a group of water-soluble pigments that provide red, purple or blue color to the leaves, flowers, and fruits. In addition, benefits have been attributed to hypertension and cardiovascular diseases. This study compared the content of total anthocyanins and volatile compounds in aqueous and ethanolic extracts of four varieties of Mexican roselle, with different levels of pigmentation. The multivariable analysis of categorical data demonstrated that ethanol was the best solvent for the extraction of both anthocyanins and volatile compounds. The concentration of anthocyanin in pigmented varieties ranged from 17.3 to 32.2 mg of cyanidin 3-glucoside/g dry weight, while volatile compounds analysis showed that geraniol was the main compound in extracts from the four varieties. The principal component analysis (PCA) allowed description of results with 77.38% of variance establishing a clear grouping for each variety in addition to similarities among some of these varieties. These results were validated by the confusion matrix obtained in the classification by the factorial discriminate analysis (FDA); it can be useful for roselle varieties classification. Small differences in anthocyanin and volatile compounds content could be detected, and it may be of interest for the food industry in order to classify a new individual into one of several groups using different variables at once.

Chemical composition and in vitro polysaccharide fermentation of different beans (Phaseolus vulgaris L.).

The composition of bioactives including polysaccharide yield and resistant starch (RS) content of 4 raw and cooked bean (Phaseolus vulgaris L.) cultivars was evaluated. Polysaccharide was fermented in vitro by incubation with human gut flora under anaerobic conditions and short-chain fatty acids (SCFAs) production was compared at 6, 12, and 24 h by gas chromatography. Polysaccharide and soluble fiber contents increased upon cooking with stachyose as the major oligosaccharide. Cooked bean of cultivar Bayo Madero had the highest yield of polysaccharides (55%) and resistant starch (37%), followed by those of Negro 8025 (48% and 32%, respectively). Acetate was the most abundant SCFAs formed in all bean varieties. The concentration of SCFAs was cultivar-dependent; Bayo Madero and Negro 8025 displayed the highest concentration of butyrate (15 mmol/L), while Azufrado Higuera had the lowest and highest concentrations of acetate (39 mmol/L) and propionate (14 mmol/L), respectively. The results suggest that the common bean is an excellent source of polysaccharides that can be fermented in the colon and produce SCFAs, compounds previously reported to exert health benefits.

Physico-chemical changes in cladodes (nopalitos) from cultivated and wild cacti (Opuntia spp.).

Physico-chemical and nutritional composition from four different nopalitos (young cladodes from cacti): Blanco sin Espinas, Blanco con Espinas, Verde Valtierrilla (cultivated materials) and a wild material from the central region of México were studied at different sizes of harvesting. The first three are commercial crops. None of the tested materials exhibited superior characteristics in all of the evaluated parameters in relation to each one of them. In various cases properties of the wild crop were comparable, if not superior, to commercial ones. Some important changes were observed in total soluble solids, water content, texture, acidity and pH as affected by size of cladode and specific crop. Most cladode samples appear to be a good source of beta-carotene and lutein. The presence of these compounds is important for human nutraceutical purposes.

Thermal and rheological properties of nixtamalized maize starch.

The effect of nixtamalization process on thermal and rheological characteristics of corn starch was studied. Starch of raw sample had higher gelatinization temperature than its raw counterpart, because, the Ca(2+) ions stabilize starch structure of nixtamalized sample; however, the enthalpy values were not different in both samples. The temperature of the phase transition of the retrograded starches (raw and nixtamalized) were not different at the storage times assessed, but the enthalpy values of the above mentioned transition was different, indicating a lower reorganization of the starch structure in the nixtamalized sample. The viscoamylographic profile showed differences between both starches, since raw starch had higher peak viscosity than the nixtamalized sample due to partial gelatinization of some granules during this heat treatment. Rheological test showed that at low temperature (25 degrees C) the raw and nixtamalized starches presented different behaviour; however, the elastic characteristic was more important in the starch gel structure. The nixtamalization process produced changes in thermal and rheological characteristics becoming important in those products elaborated from nixtamalized maize.

Accumulation, assembly, and digestibility of amarantin expressed in transgenic tropical maize.

An amaranth ( Amaranthus hypochondriacus) 11S globulin cDNA, encoding one of the most important storage proteins (amarantin) of the seed, with a high content of essential amino acids, was used in the transformation of CIMMYT tropical maize genotype. Constructs contained the amarantin cDNA under the control of a tissue-specific promoter from rice glutelin-1 ( osGT1) or a constitutive ( CaMV 35S) promoter with and without the first maize alcohol dehydrogenase intron ( AdH). Southern-blot analysis confirmed the integration of the amarantin cDNA, and copy number ranged from one to more than ten copies per maize genome. Western-blot and ultracentrifugation analyses of transgenic maize indicate that the expressed recombinant amarantin precursors were processed into the mature form, and accumulated stably in maize endosperm. Total protein and some essential amino acids of the best expressing maize augmented 32% and 8-44%, respectively, compared to non-transformed samples. The soluble expressed proteins were susceptible to digestion by simulated gastric and intestinal fluids, and it is suggested that they show no allergenic activity. These findings demonstrate the feasibility of using genetic engineering to improve the amino acid composition of grain crops.

Expression of ripening-related genes in prickly pear (Opuntia sp.) fruits.

To throw light on the expression of ripening-related genes in prickly pear (Opuntia sp.) fruits and on the possible role of the gaseous hormone ethylene in nonclimacteric fruit ripening, cDNA fragments that showed high homologies with 1-aminocyclopropane-1-carboxylate (ACC) synthase and ACC oxidase cDNAs from other plants were cloned and partially characterized. Thus, the corresponding genes were accordingly named opaccs-1 and opacco-1, after Opuntia ACC synthase-1 and Opuntia ACC oxidase-1, respectively. Southern analysis suggests the presence of at least one copy of both genes, as well as other related homologous sequences in the Opuntia genome. Northern analysis of the opaccs-1 gene shows an enhanced expression in ripening fruit tissues, whereas opacco-1 expression is highly induced in ripe tissues with respect to the green fruits and mature cladodes. These results are in agreement with an active metabolic role of ethylene during nonclimacteric prickly pear fruit ripening. This is the first report on the analysis at the molecular level of ripening-related genes of the Opuntia genus.

Functional properties of corn, banana and potato starch blends.

Potato, corn and banana starches were blended in various combinations and ratios. Stability and clarity, freeze-thaw stability, water retention capacity and apparent viscosity of the pastes (prepared with a hydrothermic treatment using 100 degrees C for 30 min) were evaluated. In general, the samples stored at room temperature (28 degrees C) presented stability as well as low retrogradation rate. However, in the samples stored at 4 degrees C the propagation and maturation of crystals in the amylopectin component were favored, increasing sample retrogradation. A synergistic effect was shown in some starch blends. The blends had poor stability to freeze-thaw cycle, but a high synergestic effect was presented in water retention capacity. Potato:banana and corn:potato blends showed a synergistic effect in the apparent viscosity and in general, starch blends had stability during the 30-min test.

Characterization of yam bean (Pachyrhizus erosus) proteins.

Seed proteins from Mexican yam bean seeds (Pachyrhizus erosus L.) were sequentially extracted according to the Osborne classification. Albumins were the major fraction (52.1-31.0%), followed by globulins (30.7-27.5%). The minor protein fraction was prolamins (0.8%). Defatting with chloroform/methanol remarkably affected the distribution of protein solubility classes; albumins were the most affected fraction (4.3-17.5%). Electrophoretic patterns of albumins showed bands at 55, 40, 35, and 31 kDa. After reduction of the globulin fraction exhibited two triplets, one from 35 to 31 kDa and the second from 19 to 21 kDa, these could be compared to the acid and basic polypeptides of 11S-like proteins. Prolamins showed one band at 31 kDa, and glutelins after reduction showed three main bands at 52, 27, and 14 kDa. Trypsin inhibitors were assayed in saline extracts; the values found (1232-2608 IU/g of meal) were lower than those of other legumes. In general, yam bean seed proteins showed an excellent balance of all essential amino acids; albumins contain the highest amount of essential amino acids.

Overexpression, purification, and in vitro refolding of the 11S globulin from amaranth seed in Escherichia coli.

An amarantin 11S globulin cDNA encoding one of the most important storage proteins of amaranth seeds, with a high content of essential amino acids, was expressed in Escherichia coli. A good level of expression of recombinant amarantin with a molecular weight of 59 kDa was obtained. The recombinant protein was extracted by ammonium sulfate precipitation and purified to homogeneity using ion-exchange chromatography and reversed phase high-performance liquid chromatography. The expressed protein exhibited electrophoretic, immunochemical, and surface hydrophobicity properties similar to those of native amarantin from amaranth seed. Also, the recombinant protein was refolded in vitro using two different methods.

Natural pigments: carotenoids, anthocyanins, and betalains--characteristics, biosynthesis, processing, and stability.

Pigments are present in all living matter and provide attractive colors and play basic roles in the development of organisms. Human beings, like most animals, come in contact with their surroundings through color, and things can or cannot be acceptable based on their color characteristics. This review presents the basic information about pigments focusing attention on the natural ones; it emphasizes the principal plant pigments: carotenoids, anthocyanins, and betalains. Special considerations are given to their salient characteristics; to their biosynthesis, taking into account the biochemical and molecular biology information generated in their elucidation; and to the processing and stability properties of these compounds as food colorants.

Acetylation and characterization of banana (Musa paradisiaca) starch.

Banana native starch was acetylated and some of its functional properties were evaluated and compared to corn starch. In general, acetylated banana starch presented higher values in ash, protein and fat than corn acetylated starch. The modified starches had minor tendency to retrogradation assessed as % transmittance of starch pastes. At high temperature acetylated starches presented a water retention capacity similar to their native counterpart. The acetylation considerably increased the solubility of starches, and a similar behavior was found for swelling power. When freeze-thaw stability was studied, acetyl banana starch drained approximately 60% of water in the first and second cycles, but in the third and fourth cycles the percentage of separated water was low. However, acetyl corn starch showed lower freeze-thaw stability than the untreated sample. The modification increased the viscosity of banana starch pastes.

Isolation and partial characterization of banana starches.

Two varieties of banana green fruit growing in Guerrero, Mexico, were used for starch isolation. Chemical analysis and physicochemical and functional properties were studied in these starches. The "macho" variety presented higher starch yield than "criollo". In general, chemical compositions in both starches were similar, except in ash content, where the "criollo" variety showed a lower value than "macho". The results of freeze-thaw stability suggested that banana starches cannot be used in frozen products. Both starches presented similar water retention capacity values that increased when temperature increased. Solubility profiles showed that at low temperature "criollo" had lower solubility than "macho", but at higher temperature an inverse behavior was evident; also the solubility increased when temperature increased. Behavior similar to that for solubility was obtained in the swelling test. The banana starch studies indicate the "macho" and "criollo" varieties have different starch structures as evidenced by viscosity.

Purification, crystallization, and preliminary X-ray characterization of a 36 kDa amaranth globulin.

The purpose of this study was to purify, crystallize, and characterize by X-ray diffraction an amaranth globulin for its subsequent structure elucidation. A 36-kDa amaranth globulin was extracted by sequential precipitation and purified by gel filtration and cationic exchange columns. It was crystallized at 18 degrees C from 4 M sodium formate. Suitable crystals for X-ray analysis were found to belong to the tetragonal crystal system with cell dimensions of a = b = 195.5 A and c = 164.14 A. Two possible tetragonal space groups P4(1)2(1)2 or P4(3)2(1)2 were determined. The crystals diffracted up to 2.5 A.

Evaluation of some cereals, plants and tubers through protein composition.

Wild and cultivated maize, sorghum, rice, amaranth, soybean, and cassava were screened for variability in seed storage proteins. Total seed proteins, albumin (Alb-1 and Alb-2), globulin, alcohol-soluble (A1 and A2), and glutelin (G1 and G2) fractions were investigated by means of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The comparison was done by the obtained protein patterns and their relative amounts. Using quantitative analysis of the protein composition and the electrophoretic patterns, the relationships between total proteins and amount of individual proteins were determined. Electrophoretic patterns of extracted proteins from investigated samples showed that the main protein subunits were concentrated between 10 and 45 kDa. Variation was found in major fractions and minor bands. Electrophoretic patterns of the protein fractions are directly related to the genetic background of the protein and can be identified and used to certify the genetic makeup of wild, cultivated, or newly derived cereals and plants.

Stability of some Cactaceae proteins based on fluorescence, circular dichroism, and differential scanning calorimetry measurements.

Characterization of three cactus proteins (native and denatured) from Machaerocereus gummosus (Pitahaya agria), Lophocereu schottii (Garambullo), and Cholla opuntia (Cholla), was based on electrophoretic, fluorescence, CD (circular dichroism), DSC (differential scanning calorimetry), and FT-IR (Fourier transform infrared) measurements. The obtained results of intrinsic fluorescence, DSC, and CD were dissimilar for the three species of cactus, providing evidence of differences in secondary and tertiary structures. Cactus proteins may be situated in the following order corresponding to their relative stability: Machaerocereus gummosus (Pitahaya agria) > Cholla opuntia (Cholla) > Lophocereu schottii (Garambullo). Thermodynamic properties of proteins and their changes upon denaturation (temperature of denaturation, enthalphy, and the number of ruptured hydrogen bonds) were correlated with the secondary structure of proteins and disappearance of alpha-helix.

Computational analysis of the amino acid residue sequences of amaranth and some other proteins.

Amaranth belongs to a nutritious class of pseudocereals. The well balanced amino acid composition of amaranth compared with those of major cereals would indicate that it deserves a quantitative study of its chemical properties. This work was undertaken to compare Amaranthus (A.) caudatus with a number of other plants on the basis of the sequences of various proteins and the composition of their alcohol-soluble protein mixture and glutelins. Alcohol-soluble proteins were extracted with 55% isopropanol (2-ProOH) + 5% 2-mercaptoethanol (2-ME) and glutelin fractions were obtained with borate buffer + 3% 2-ME + 0.5% sodium dodecyl sulfate (SDS), pH 10. Protein fractions were then electrophoreded on sodium dodecyl sulfate polyacrylamide gels (SDS-PAGE). FASTA and TFASTA programmes were used for comparison of amino acid sequences. Dot matrix analysis and secondary structure predictions which were drawn by Plot-structure, were taken from the GCG package. Electrophoretic tests failed to indicate significant correlation between prolamins from cereals and other plants with the alcohol-soluble fractions from amaranth, proving that these proteins cannot represent the main fraction in amaranth. On the other hand, glutelins shared some common electrophoretic bands with other cereals and showed some identity by SDS-PAGE. Amino acid sequences of A. caudatus (100% identity) had degrees of similarity in the range of 71.4 to 52.2% with rice, garden pea, jobs' tears, maize, and yam. Rice glutelin had similarity in the range of 93.3% to 44.8% with oats, soybean, and pea. Secondary structures of A. caudatus (using conservative amino acid replacement), jobs' tears and rice glutelins, oat globulin, and pea legumin sequences were predicted. Some relationship was shown among electrophoretic patterns of alcohol-soluble proteins and glutelins of A. caudatus.

Effects of Sunlight Illumination of Marigold Flower Meals on Egg Yolk Pigmentation.

The effect of sunlight illumination of marigold flower meal on the pigmentation of feed for laying hens and of their resulting egg yolks was evaluated by high-performance liquid chromatography and by subjective and light reflectance colorimetry techniques. Illumination did not have an effect on the identity of carotenoids in the flower meal. Interestingly, illuminated marigold flower meals yielded an oleoresin with a higher all-trans-zeaxanthin level, with respect to meals kept in darkness. A higher level of all-trans-zeaxanthin was also present in feed pigmented with that oleoresin. Additionally, this pigmented feed showed the best color values and resulted in egg yolks with good color; remarkably, these egg yolks had a low pigment content with respect to control treatments. Thus, sunlight illumination of marigold flower meal showed a positive effect on egg yolk color; the main factors contributing to this effect were not the identity or quantity of carotenoids in laying hen feed or egg yolks, but rather other as yet unidentified marigold component(s) which was (were) somehow influenced by sunlight illumination.

Enzymatic treatment to enhance carotenoid content in dehydrated marigold flower meal.

The effect of enzymatic treatments using a commercial enzyme (Econase-cep at pH 5.0 and 0.1% w/w concentration) at different levels of dehydrated marigold meal (5, 10, 15 and 20% dry weight), to enhance carotenoid extraction, was evaluated. The AOAC method consisting of a simultaneous extraction and saponification by using hexane-ethanol-acetone-toluene (10:6:7:7 v/v) and metanolic KOH (40% w/v) was used to evaluate the carotenoid content. The measurement of carotenoids was also carried out in samples in which the water soluble compounds were previously eliminated (AOAC-H2O). Total carotenoids ranged from 11.4 to 17.4 g/kg and 18 to 24.7 g/kg of control and treated marigold meal, respectively. Highest amount of carotenoids were noted when 5% level of treated meal was used.