In vitro digestibility,structural and functional properties of starch from pigeon pea (Cajanus cajan) cultivars grown in India

Starches isolated from two pigeon pea cultivars (AL-15 and AL-201) were evaluated for their in vitro digestibility, structural and functional properties. Both the cultivars exhibited a characteristic C-type diffraction pattern with relative crystallinity values of 31.9% and 34.2%, for AL-15 and AL-201, respectively. The structural characterization obtained using high performance size exclusion column chromatography revealed that molecular weight of amylopectin and amylose was higher for AL-201 (396 and 3.92 × 10⁶ g/mol, respectively) in comparison to AL-15 starch (354 and 3.31 × 10⁶ g/mol, respectively). AL-201 exhibited higher values for transition temperatures, enthalpy of gelatinization, pasting temperature and percentage retrogradation in comparison to AL-15 starch. Slowly digestible starch, readily digestible starch and resistant starch contents of AL-15 and AL-201 cultivars were observed to be 31.0, 8.1 and 60.9% and 29.6, 5.2 and 65.2%, respectively. The hydrolysis index and RS values indicated that pigeon pea starches were highly resistant to digestion.     

Physicochemical properties of Pinhão (Araucaria angustifolia, Bert, O. Ktze) starch phosphates

Physicochemical properties of pinhão (seeds of Paraná pine) starch phosphates were evaluated and compared to corn starch phosphates. The phosphorylation process used yielded starch phosphates with three different degrees of substitution (DS): low (0.015), medium (0.07) and high (?0.12). Medium and high DS starch phosphates had higher cold water binding capacity, swelling power, and paste clarity, but lower paste syneresis (at 5 °C and after freeze-thaw cycles) than native starches (P<0.05). Low, medium, and high DS corn starches had higher solubility than native starches (3.8-, 8-, and 6-fold higher; P<0.05), but the solubility of pinhão starch increased only in medium DS starch phosphates (3-fold higher; P<0.05). Low DS starch phosphates had viscosity curves similar to native starches. In contrast, medium and high DS starch pastes had peak viscosity at room temperature, reached the minimum viscosity when heated to 95 °C, and had low setback.     

Starch enzymatic hydrolysis,structural, thermal and rheological properties of pigeon pea (Cajanus cajan) and dolichos bean (Dolichos lab-lab) legume starches

Cajanus Cajans and Dolichos lab-lab legume starches from Argentine cultivars were investigated under a technological and nutritional point of view. Their physico-chemical, structural, thermal and the rheological properties of their gels were evaluated. Rice (RS) and potato (PS) starches were included as references. In vitro digestibility from Englyst method was also evaluated. Legume starches had the highest amylose content and the most stable chemical structure. Their rapidly digestible starch and starch digestibility rate index were very low, similar to PS, and fivefold lower than RS. They had a much higher slowly digestible starch content than PS. Legume starches showed the highest gel stability versus heating and stirring and an intermedium pasting temperature between RS and PS. They formed viscoelastic gels at 6% concentration with stronger elastic-like behaviour and higher yield stress than references. Our results indicate these legumes represent an efficient starch source to provide tailor-made properties to food/industrial applications.     

Influence of certain physico-chemical treatments on the cookability of pigeon pea (Cajanus cajan)

The influence of sodium hexametaphosphate (SHMP) and trisodium citrate (TSQ on the cookability of split cotyledons (dhal) of pigeon pea was studied. The former was found to be more effective in reducing the cooking time than the latter chemical when added to the cooking water at (85 ± 1)°C at 2% level of concentration. Influence of certain physicochemical treatments involving presoaking, freezing, thawing, and controlled drying on the cookability of the pigeon pea dhal was also investigated. Presoaking in a salt solution followed by either controlled drying alone or freezing, thawing and controlled drying in succession resulted in quick-cooking dhal.     

Effects of NaCl,ionic strength and pH on the foaming and gelation of pigeon pea (Cajanus cajan) protein concentrates

Studies were carried out on the effects of pH, ionic strength, sample concentration and added salt (NaCl) concentration on two hydrodynamic properties — gelation capacity and foaming properties of pigeon pea protein concentrates. Results indicate that the protein concentrate has a good gelation capacity with a least gelation concentration of 6% (w/v). Using the least concentration endpoint (LCE) as an index of gelating ability, the gelation capacity of the flour improved in the presence of moderate NaCl concentration and low ionic strength. Acidic and neutral pH also enhanced gelation while alkaline pH decreased it. The foaming capacity of the flour could be improved in a medium of low ionic strength and by increasing the concentration of protein sample as well as by a moderate concentration (0.25% w/v) of NaCl. Better foaming capacity was observed in the acidic region than in the alkaline region. Foams were also observed to be more stable as concentration of NaCl, concentration of protein concentrate and ionic strength increased.     

Effect of several pre-treatments on the physical characteristics of dehulled fraction of pigeon pea (Cajanus cajan L)

Processing of pigeon pea ( Cajanus cajan L.) involves pre-treatment in order to loosen the hull, followed by dehulling. In this study, different pre-treatments were investigated and different parameters such as moisture gain, temperature change during different steps of processing and dehulled fractions were measured and analysed. The highest temperature observed after pre-treatment was 92.1 °C and the lowest was 24.6 °C, for hydrothermal and wet methods, respectively. It was found that the hydrothermally treated pigeon pea gave the highest amount of dehulled grains, followed by the dry method. There were higher amounts of brokens (17.6 g) in case of wet method and lower (6.2 g) in case of dry method. Hydrothermal treatment was found suitable when compared with other pre-treatments. Cooked samples were tested against a 9-point hedonic scale and hydrothermally treated samples were found to have better acceptability.     

The physico-functional characteristics of starches from cowpea (Vigna unguiculata), pigeon pea (Cajanus cajan) and yambean (Sphenostylis stenocarpa)

Starches fractionated from cowpea (Vigna unguiculata, Ife Brown), pigeon pea (Cajanus cajan, Cita II) and yambean (Sphenostylis stenocarpa) were comparatively studied for physical and functional properties, including granule morphology, granule sizes, water absorption capacity, water–oil absorption index, swelling capacity, ionic property, bulk density and amylographic viscosities. The three legume starch granules range in diameter size from 5–57.5 μm. The water absorption capacities of all the starches were generally low at room temperature up to 70°C. Pigeon pea starch was the least susceptible to swelling while the cowpea starch was the most susceptible. The starches displayed non-ionic character, low water activity, high bulk density, water and oil absorption capacities and type C Brabender visco-amylograms at 6.2% starch-water slurry (on dry wt basis). ©     

Physicochemical and functional properties of makal (Xanthosoma yucatanensis) starch

Physicochemical and functional properties of makal (Xanthosoma yucatanensis) starch were determined. Granules were oval in shape and 12.4 μm average diameter. Starch purity was high (96.7%) with low protein (0.1%), fat (0.2%), fibre (0.4%) and ash (0.1%) contents. Amylose content was 22.4%. The gelatinization temperature was 78.5 °C and transition enthalpy was 15 J/g. At 90 °C, solubility was 32.9%, swelling power was 28.6 g water/g starch and water absorption capacity was 19.2 g water/g starch. Pasting characteristics were: temperature 75 °C, maximum viscosity 280 BU, breakdown −8 BU, setback 180 BU and consistency 172 BU. Clarity, expressed as transmittance, was 35.8%. Gel deformation was 20.8% with a 0.03 kgf maximum load. Makal starch’s high gelification temperature and firmness make it appropriate for use in high temperature food systems, but its low stability in refrigeration and freezing cycles make it inadequate for use in foods subject to those conditions.     

Physicochemical characteristics of waxy rice starch influencing the in vitro digestibility of a starch gel

Starches were isolated from three waxy rice varieties: Koganemochi (Kog), Hakuchomochi (Hak), and Kantomochi 172 (K172). Forty percent starch gels were prepared and the extent of starch gel digestibility was determined by an in vitro method. The distribution of chain lengths of amylopectin was analyzed and differential scanning calorimetry was used to analyze gelatinization and retrogradation of waxy rice starch. The K172 gel had significantly higher resistance to hydrolysis than had the other gels. The K172 starch contained lower proportions of the short chains of amylopectin and showed higher gelatinization temperature and enthalpy. The retrogradation peak was measured using waxy rice starch gels stored for 1 and 7 days at 5 °C. The K172 gel was observed to retrograde more quickly and to have a greater extent of retrogradation than the other gels. The difference in amylopectin chain length distribution and recrystallinity contributed to the variation in the starch gel digestibility of waxy rice.     

Effect of bicarbonate soaking on dehusking efficiency and composition of pigeon pea (Cajanus cajan L.) seeds and dhal

Soaking pigeon pea seeds in 6% sodium bicarbonate solution for 1 h, followed by oven-drying to 10% moisture improved dehusking efficiency from 66% in untreated seeds, or 71% in water-soaked seeds similarly dried, to 94% yield of dhal. Treatment reduced gum and pectin content, increased enzyme activity, but caused losses in protein and starch content of the dhal.     

Domestic processing effects on available carbohydrate content and starch digestibility of black grams (Vigna mungo) and chick peas (Cicer arietium)

Domestic processing effects on available carbohydrate contents and starch digestibility of black grams and chick peas were investigated. The food legumes were soaked in tap water and alkaline solution of sodium bicarbonate at 30 and 100 °C for 1–2 h before cooking under pressure. Total soluble sugars, reducing sugars and starch contents of black grams and chick peas were 9.64% and 9.83%, 0.78% and 0.83%, 43.0% and 44.3%, respectively. All these available carbohydrate contents of black grams and chick peas were reduced to various extents as a result of soaking and cooking. At 30 °C, 4.46% of total soluble sugars, 3.84% of reducing sugars and 6.86% of starch contents were reduced on soaking the black grams in tap water for 1 h. Available carbohydrate contents were further reduced when soaking time and temperature of the food legumes was increased before cooking. About 3.43–25.0% of total soluble sugars and 4.26–22.7% of starch contents were lost on soaking black grams and chick peas in tap water and sodium bicarbonate solution. Maximum amounts of total soluble sugars (28.5–59.6%) and starch contents (29.9–67.4%) were lost on cooking the water- and alkali-soaked food legumes. However, these losses were comparatively less with the water soaking process. Besides these losses, starch digestibilities of black grams and chick peas were markedly improved as a result of cooking. However, no appreciable improvement in the starch digestibility was observed after soaking these food legumes in water or alkaline solution.     

Starch hydroxyalkylation: Physicochemical properties and enzymatic digestibility of native and hydroxypropylated finger millet (Eleusine coracana) starch

Starch was isolated from finger millet (Eleusine coracana) and it was etherified with propylene oxide to produce hydroxypropylated derivative. The specific specie used in this study is African finger millet known as jeero. The yield of starch obtained from finger millet on dry weight basis was 52.4%. Progressive increases in molar substitution (MS) were observed as the volume of propylene oxide added to the reaction medium increased. The X-ray pattern of native finger millet starch conforms to the ‘A’ diffraction pattern characteristics of cereal starches. Prominent peaks were observed at around 2θ=15°, 17°, 18° and 23° and weaker peaks at around 2θ=20° and 26°. No pronounced differences were observed between the diffractograms of native starch and the hydroxypropyl derivatives. Hydroxypropylation improved the free swelling capacities of the native starch at all temperatures studied (30–90 °C). Turbidity of unmodified finger millet starch paste increased progressively as the days of storage increased. Turbidity reduced remarkably after hydroxypropylation and reduction in turbidity was observed as the MS of the modified starches increased. Hydroxypropylation reduced pasting temperature, increased peak viscosity but reduced setback value. In addition, hydroxypropylation reduced percentage syneresis of the unmodified starch. Retrogradation properties monitored with differential scanning calorimetry reveals that starch retrogradation reduced reasonably after hydroxypropylation. Carbon 13 NMR spectroscopy reveals that hydroxypropylation took place predominantly on carbon 6 on the anhydroglucose unit (AGU).     

Optimization of process parameters for the development of a cheese analogue from pigeon pea (Cajanus cajan) and soy milk using response surface methodology

Response surface methodology was used to optimize starter culture concentration (3–7%), pigeon pea–soy solids ratio (1 : 0.3–1 : 1.1), pigeon pea–water ratio (1 : 12–1 : 9), incubation temperature (37–45C) and coagulation temperature (75–95C) in the development of a cheese analogue from pigeon pea and soy milk. Pigeon pea milk and soy milk were prepared by a hot water grinding method, followed by filtration and inoculation. Cheese analogue was obtained through coagulation of the fermented milk by boiling for 15 min, followed by filtration using double-layered muslin cloth and pressing at 1 kg/cm ² pressure for 1 h. The results showed that the total solids recovery (TSR), protein content, fat content and pH varied from 51.09–62.61%, 40.04–55.93%, 9.35–15.36% and 4.48–4.9, respectively, depending on the experimental conditions. The optimum conditions of process parameters for maximum total solids recovery were 6.0% starter culture concentration, 1 : 0.4 pigeon pea–soy solids ratio, 1 : 11 pigeon pea–water ratio, 40.5C incubation temperature and 88.5C coagulation temperature.     

Effect of endosperm type on texture and in vitro starch digestibility of maize tortillas

Tortilla is the main staple of Mexico and it is made using diverse maize varieties, which have different endosperm types. Three maize varieties with vitreous, intermediate and floury endosperms were used. Texture and starch digestibility were evaluated in freshly prepared and stored tortillas for 24, 48 and 72 h. Tortilla made with maize of vitreous endosperm had the highest force to rupture and the lowest distance of elongation, indicating more rigid texture. Stored tortillas had lower available starch content and higher effect was shown by tortilla of vitreous endosperm, pattern that agrees with the higher increase in the resistant starch content with the storage time. Fresh tortilla of floury endosperm showed the highest hydrolysis rate during the first 15 min followed by tortillas of intermediate and vitreous endosperms. Starch hydrolysis values decreased when storage time increased, in agreement with the resistant starch content in the stored tortillas. At the longest storage time (72 h) tortilla of floury endosperm presented higher hydrolysis rate, followed by tortilla of intermediate and vitreous endosperms. The endosperm type plays an important role in the textural and starch digestibility of fresh and stored tortillas.     

Further characterisation of protease inhibitors from pigeon pea (cajanus cajan (l) millsp) seeds

Cajanus trypsin inhibitor (CTI) and Cajanus trypsin-chymotrypsin inhibitor (CTCI) previously purified from cv TAT-10 were further characterised. The modification of the inhibitors revealed the presence of lysine at the trypsin reactive site in both CTI and CTCI. Modification of tyrosine at the reactive site of CTCI did not abolish chymotrypsin inhibition suggesting the presence of leucine or phenylalanine as reported in other chymotrypsin inhibitors. CTCI did not contain tryptophan. Dissociation constants for the inhibitors with bovine trypsin were in the region of 0.69 nmol (CTCI) and 0.029 nmol (CTI). Although the protease inhibitors lost their inhibitory activity on exposure to 2-mercaptoethanol they remained attached to the enzyme. The inhibitors were not very effective against the protease from Helicoverpa armigera which is a serious field pest of Cajanus. Dissociation constants for the inhibitors with the larval enzyme were in the region of 100 nmol.     

Influence of non-starch polysaccharides on the in vitro digestibility and viscosity of starch suspensions

The effects of adding non-starch polysaccharides (xanthan gum, guar gum, konjac glucomannan, and pectin) on the starch digestibility and viscosity of raw starch suspensions in a mixed system were determined. Each type of polysaccharide was added to high-amylose corn starch suspensions at defined concentrations. High-amylose rice starch suspensions mixed with xanthan and guar gum were prepared for comparison. The extent of starch digestibility was determined by an in vitro method, and the glucose diffusibility from the dialysis tube in the presence of polysaccharides was measured. The added polysaccharides were observed to decrease the starch digestibility in a mixed system. When compared at the same concentration, xanthan gum showed the most pronounced suppressive effect on starch digestibility and glucose diffusibility from the dialysis tube. The addition of polysaccharides increased the viscosity of the starch suspension. Significant relations were found between the extent of starch digestibility and the apparent viscosity at low shear rate.     

Purification and characterisation of protease inhibitors from pigeon pea (cajanus cajan (l) millsp) seeds

Two protease inhibitors from Cajanus cajan seeds have been purified to homogeneity by trichloroacetic acid (TCA) solubilisation, ion-exchange and gel-filtration chromatography followed by preparative polyacrylamide gel electro-phoresis. One of the inhibitors, Cajanus trypsin-chymotrypsin inhibitor (CTCI), inhibits both bovine trypsin and chymotrypsin while the other, Cajanus trypsin inhibitor(CTI), inhibits only bovine trypsin. The two inhibitors contained no carbohydrate and had an isoelectric point of 6. CTCI and CTI had average molecular weights of 15000 and 10500, respectively. The purified inhibitors in solution were stable to heat at 80°C for 15 min and pH 7–10. In the pH range 3–5, 80% of the activity was retained. Autoclaving totally destroyed the inhibitor activity. CTCI had two sites for trypsin binding and one site for chymotrypsin binding while CTI had only one site for trypsin binding. The inhibitors were very specific towards mammalian serine proteases and did not inhibit other proteases or serine proteases of bacterial origin.