Constitution of leguminous seeds: The microscopic structure of proteins isolated from Phaseolus beans

Proteins were isolated from citric acid and sodium hydroxide extracts of Phaseolus beans. Examination of the proteins under the light microscope revealed that they had different micro-structures. Bipyramidal crystalline and spheroidal protein were obtained from the citric acid extracts of the white kidney bean, the navy bean and the baby lima bean. Cubical crystalline, rosette-type and needle-like structures were isolated from the navy bean under certain conditions. Analysis of the proteins revealed the presence of phytic acid and carbohydrate material. There was some indication that neither of these two materials affect the microscopic structure of the proteins.     

Constitution of leguminous seeds. Scanning electron microscopy of proteins prepared from Phaseolus beans

Proteins were isolated from citric acid and sodium hydroxide extracts of navy beans (Phaseolus vulgaris), white kidney beans (Phaseolus vulgaris) and baby lima beans (Phaseolus lunatus). Examination of the proteins under the scanning electron microscope revealed that several types of particulate micro-structures were present in the proteins obtained by citric acid extraction of the beans followed by precipitation by cooling. Examination of the proteins obtained by extraction with sodium hydroxide solution and isoelectric precipitation revealed the presence of only one type of non-particulate micro-structure.     

Fractionation of Algerian common wheat proteins by HPLC and sodium dodecyl sulfate-polyacrylamide gel electrophoresis; relationship with technological quality

Sixteen Algerian common wheat genotypes have been analysed during three harvests for their protein characteristics. SE- HPLC analysis showed some relation between the percentages or the absolute amounts of the glutenin fractions F1, F2 or F1/F2 ratio and several technological parameters. However, the relative amount of SDS unextractable polymeric glutenins in total polymeric glutenins or in total polymeric proteins and the ratios of the SDS unextractable proteins, extracted from the residues after sonication, in extracted total polymeric proteins seem to play a more determinant role in wheat strength. If no interesting links were observed between the HMW/LMW glutenin ratios determined by RP-HPLC and the technological quality characteristics, HMW glutenin SDS-PAGE analysis and technological and biochemical tests once more showed the superiority of the 5+10 HMW glutenin subunit pair compared with 2+12 allelic pair in the determination of the strength, its aptitude to give more aggregate of large molecular sizes, and higher HMW/LMW glutenin ratios.     

Tryptic fragments of phaseolin from protein isolates of Phaseolus beans

Crystalline and amorphous protein isolates from white kidney and navy beans (Phaseolus vulgaris) and baby lima and large lima beans (Phaseolus lunatus) were subjected to tryptic hydrolysis. The hydrolysis was monitored by the nitrogen solubility index (NSI) and reverse phase-high performance liquid chromatography/mass spectrometry (RP-HPLC/MS) analysis of the hydrolysates. The results of the NSI and RP-HPLC showed that the tryptic fragments of the crystalline isolates possessed higher solubility properties than the fragments of the amorphous isolates. The results of the MS study of phaseolin peptides in the RP-HPLC fractions of the hydrolysates showed that trypsin-specific bonds located in β-structured regions of β-phaseolin are resistant to tryptic hydrolysis, and that the most susceptible bonds to trypsin hydrolysis are located in regions not directly involved in the formation of secondary structural units, but in regions of disordered structure, or in regions interconnecting secondary structural units. Some trypsin-specific bonds located within α-helical structures were also cleaved by trypsin hydrolysis.     

Influence of naturally acid-soluble proteins from beans (Phaseolus vulgaris L.) on in vitro digestibility determination

The in vitro digestibility of bean (Phaseolus vulgaris) protein fractions was studied using a pepsin-pancreatin system. Enzymatic hydrolysis was stopped by adding a strong acid and the extent of proteolysis determined by measurement of free amino groups in the soluble fraction. The in vitro digestibility of bean protein fractions was low when in the native state and was differently affected by denaturation. For phaseolin, the main reserve protein, heating caused a significant increase of susceptibility to hydrolysis, whereas heat had no apparent effect on digestibility of glutelins and albumins (II). For the PIL (protease inhibitor-lectin rich) fraction, which was shown to have a composition similar to total albumins, there was a decrease of digestibility, probably associated to disulfide bond formation upon heating. Results of in vitro digestibility were shown to be strongly dependent on the utilization of a sample blank to account for proteins naturally soluble in the acid used to interrupt hydrolysis, which would otherwise be estimated as digested protein. These proteins are characterized by a high carbohydrate content, probably responsible for their high solubility and low digestibility.     

Structure-modifying alkaline and acidic pH-shifting processes promote film formation of soy proteins

The effect of pH-shifting, a process that induces the molten globule state in proteins, on the film-forming potential of soy protein isolate (SPI) at different temperatures was investigated. Partial unfolding at pH 1.5 or 12, followed by refolding at pH 7.0, was performed to alter the protein structure. Glycerin-plasticised films were prepared from pH-treated SPI at ambient temperature (20 °C), or by heating at 50, 60, 70, or 80 °C (30 min). Tensile strength (TS), elongation at break (EAB), water vapour permeability (WVP), protein solubility (pH 3–7), and non-participating proteins of films were analysed, and the film microstructures were examined. The pH₁₂-treated SPI spontaneously formed a transparent, slightly yellowish film at 20 °C, which had the greatest EAB, while pH_1.5-treated and native SPIs required preheating at 50 and 70 °C, respectively, to form a film. Heating generally decreased solubility and WVP but increased TS. Films formed from both pH₁₂- and pH_1.5-treated SPIs were more elastic (up to 2-fold greater in EAB, P < 0.05) than the film formed from untreated SPI despite slightly reduced TS and WVP. Electrophoresis revealed disulphide bonds between A and B subunits of glycinin being a dominant force in pH₁₂- and pH_1.5-treated SPI films, while noncovalent forces were abundant in untreated SPI films. The pH₁₂-treated SPI film consisted of more interactive protein strands than other SPI films, which seemed to explain its superior elastic properties.     

Dry beans of Phaseolus. A review. Part 1. Chemical composition: proteins

Beans of Phaseolus are important food crops both economically and nutritionally and are cultivated and consumed worldwide. With ever‐rising costs of meats and fresh fruits and vegetables, dry beans are expected to contribute more to the human nutrition in coming years. Traditionally, they have been referred to as “poor man's meat” and have contributed significantly to the diets of many people of several countries in Asia, Africa, Middle East, and South America. In recent years, a renewed interest in bean research in Western European countries and the U.S. is evident. In this review, certain biochemical, technological, nutritional, and toxicological aspects are discussed and the limitations and problems associated with dry beans of Phaseolus as human food are addressed.     

Constitution of leguminous seeds. The effect of some physico-chemical factors on the yield of proteins isolated from Phaseolus beans

The yields of acid-soluble proteins isolated from white kidney beans (Phaseolus vulgaris), navy beans (P. vulgaris) and baby lima beans (P. lunatus) were determined under different conditions of extraction. Highest yields of protein material were obtained when malic acid solutions [0.4M (pH 3.5) white kidney bean and navy bean; 0.05M (pH 3.5) baby lima bean] were used and under the following conditions: shaking time 20-30 min; extraction temperature 40-45°C; particle size 0.50-1.00 mm.     

The effect of cooking with kanwa alkaline salt on the chemical composition of black beans (Phaseolus vulgaris)

The effect of cooking with kanwa alkaline solution on the chemical composition of black beans (Phaseolus vulgaris) was analyzed. Crude lipids and water-soluble fractions were extracted from three flour samples obtained from raw black beans and black beans cooked in kanwa solution or distilled water. Heat processing resulted in significant reduction in crude lipids, proteins and neutral sugars. Neither heat treatment induced changes in the levels of palmitic, stearic, oleic or linoleic acids, present in the crude lipid fraction. There was a significant change in both the total amino acids and the total essential amino acids. Heat treatment in alkaline solution decreased the levels of isoleucine, lysine, tyrosine, phenylalanine, threonine and valine. There was also a decrease in the galactose content after this heat processing.     

Flavour release from rehydrated French beans (Phaseolus vulgaris) influenced by composition and volume of artificial saliva

Influence of saliva composition and volume on flavour release from rehydrated French beans (Phaseolus vulgaris) was studied in three types of mouth model systems; dynamic headspace (DH), dynamic headspace and mastication (DHM) and a purge-and-trap (PT) model system. Volatile compounds were analysed by gas chromatography, using flame ionization detection (FID), mass spectrometry and sniffing port detection. Areas of FID peaks were largest in the PT system, followed by those of the DHM and DH systems, respectively. Saliva composition as well as volume influenced the release of volatile compounds from rehydrated French beans. Generally, FID data showed a decrease in release by the saliva component mucin, because of interactions between volatile compounds and protein, and an increase in release by its α-amylase, probably due to degradation of inclusion complexes of starch. The decrease in flavour release by the enlarged saliva volume was evaluated by a model study. Sniffing patterns of odour active compounds were barely influenced by either saliva composition or volume.     

Constitution of leguminous seeds. Polyacrylamide-disc gel electrophoresis of acid soluble and acid precipitated proteins prepared from baby lima beans

Acid soluble proteins (bipyramidal crystalline, 76.9% protein, 15% carbohydrate) prepared by citric acid extraction and acid precipitated proteins (amorphous, 64.2% protein, 11.3% carbohydrate) prepared by alkali extraction from baby lima beans (Phaseolus lunatus) were found to behave in a similar manner under alkaline conditions (pH 8.9) of electrophoresis (absence of urea). Striking differences were observed in the behaviour of the two types of protein preparations when electrophoresis was performed under acidic conditions (pH 4.5; absence and presence of urea and a mixture of urea and 2-mercaptoethanol) and in the presence of sodium dodecyl sulphate.     

Thermal inactivation kinetics of peroxidase and lipoxygenase from fresh pinto beans (Phaseolus vulgaris)

 Thermal inactivation kinetics of crude peroxidase (POX) and lipoxygenase (LOX) in fresh pinto beans were studied over the temperature range of 55–90°C. The inactivation of both enzymes followed first-order kinetics. The biphasic inactivation curves for POX indicate the existence of several isoenzymes of varying heat stability. In the temperature range of 55–70°C, the activation energies (E _a) of POX were 46.5 kcal·mol^–1 for the heat-labile portion and 37.6 kcal·mol^–1 for the heat-stable portion. On the other hand, the LOX enzyme had an E _a value of 42.26 kcal·mol^–1 at 55–75°C and 49.1 kcal·mol^–1 at 55–90°C. Received: 28 July 1997 / Revised version: 16 October 1997     

Thermal inactivation kinetics of peroxidase and lipoxygenase from fresh pinto beans (Phaseolus vulgaris)

 Thermal inactivation kinetics of crude peroxidase (POX) and lipoxygenase (LOX) in fresh pinto beans were studied over the temperature range of 55–90°C. The inactivation of both enzymes followed first-order kinetics. The biphasic inactivation curves for POX indicate the existence of several isoenzymes of varying heat stability. In the temperature range of 55–70°C, the activation energies (E _a) of POX were 46.5 kcal·mol^–1 for the heat-labile portion and 37.6 kcal·mol^–1 for the heat-stable portion. On the other hand, the LOX enzyme had an E _a value of 42.26 kcal·mol^–1 at 55–75°C and 49.1 kcal·mol^–1 at 55–90°C. Received: 28 July 1997 / Revised version: 16 October 1997     

Identification and quantification of soluble sugars in green beans by HPLC

An HPLC method has been performed and validated for soluble sugar analysis in green bean samples (Phaseolus vulgaris cv. Perona), with good linearity, accuracy and precision. Monosaccharides (fructose and glucose), disaccharide (sucrose) and the polyalcohol (myo-inositol) were identified in green beans samples, as well as two unknown compounds, whose content was less than 16% of total soluble sugars. Enzymatic assays using !-glucosidases were performed in order to clarify the identity of one of the components of this fraction (identified as myo-inositol). In all the batches of green beans analysed, fructose was the major sugar (0.88-1.44%), while sucrose (0.10-0.39%) and myo-inositol (0.08-0.66%) presented higher variability on the analysed samples.     

Extraction and characterization of pectic polysaccharides from easy- and hard-to-cook common beans (Phaseolus vulgaris)

The occurrence of the hard-to-cook (HTC) defect in legumes is characterized by the inability of cotyledons to soften during the cooking process. This phenomenon may be influenced by pectin properties. The objective of this study was to characterize the pectic polysaccharides comprised in the alcohol insoluble residue (AIR) extracted from easy-to-cook (Rose coco) and hard-to-cook (Pinto) common beans. This would provide an insight in the relationship between the pectin properties and HTC defect. The AIR was extracted from raw, half-cooked hard, half-cooked soft and fully-cooked bean samples. Subsequently, it was fractionated into water-, chelator- and Na₂CO₃-soluble pectin fractions and a hemicellulose fraction. For the AIR and the pectin fractions, determination of the galacturonic acid content, neutral sugars, degree of methylesterfication (DM), degree of acetylation (DAc) and molar mass (MM) distribution was performed. Results on the pectin fractions, MM distribution and pectin content profile, revealed that Rose coco pectin generally showed higher pectin solubility than Pinto. Neutral sugar profiles indicated that Pinto contained higher amounts of branched pectin (i.e. arabinans) than Rose coco. There was no difference between the DM of Pinto and Rose coco, however, the DAc was higher in Rose coco. In conclusion, the differences in pectin structure and solubility properties between easy- and hard-to-cook common beans might contribute to the differences in their cooking behavior.     

不同豆类中4种大豆异黄酮的HPLC法测定

建立同时测定豆类中4种大豆异黄酮成分含量的高效液相色谱法,探讨了该方法的最佳测定条件,结果显示,70％的乙醇在60℃超声提取40min时,效果最佳。该方法简便、灵敏、准确,适用于豆类中4种大豆异黄酮成分的含量测定和产品质量控制。     

Recovery of proteins from fish waste products by alkaline extraction

 Waste from fish-filleting units is used in the production of fish meal or directly used in animal feeds but more frequently is simply discarded. In order to upgrade the by-products of the filleting of hake and monkfish, a systematic study was made of the recovery of proteins by chemical extraction and precipitation with HCl and sodium hexametaphosphate [Na₆(PO₃)₆]. The extraction process was studied to determine the effect of pH, type of alkaline solution used [NaOH or Ca(OH)₂], concentration of NaCl, ratio of extracting media to raw material, and temperature on the percentage of protein solubilised. Proteins present in the extract were recovered by precipitation with HCl and the effect of pH on the percentage recovered was examined. The effect of Na₆(PO₃)₆ concentration on the recovery of soluble proteins present in the supernatant after isoelectric precipitation was also studied. The raw material and products were characterised by their approximate chemical composition and amino acid profile. Received: 12 January 1999 / Revised version: 8 April 1999