Francisco Millán

Protein isolates from chickpea (Cicer arietinum L.): chemical composition, functional properties and protein characterization

Two types of protein isolates were prepared from ground chickpea seeds by alkaline extraction, with (Isolate-B) and without (Isolate-A) sodium sulphite, and acid precipitation of the proteins at the isoelectric point (pI 4.3). The percentage of protein recovered from chickpea flour in the preparation of Isolates-A and B were 65.9 and 62.1%, respectively. Chemical composition, main functional properties and protein composition of chickpea flour and protein isolates were determined. Isolates-A and B contained 78 and 88.1% of protein, respectively, and had a balanced content of essential amino acids, with respect to the FAO pattern. The in vitro protein digestibility ranged between 95.6 and 96.1%. Isolate-A showed a partial dissociation of the 11S protein because of the high pH used for the protein extraction, and this probably explains the differences observed in the functional characteristics of both isolates.

Production of ace inhibitory peptides by digestion of chickpea legumin with alcalase

Abstract Short peptides from different sources have proved to be very efficient inhibitors of the angiotensin I-converting enzyme, an enzyme with a major role in the regulation of blood pressure. These peptides are of therapeutic value, so that the possibility of obtaining such peptides by treatment of chickpea legumin with the protease alcalase has been explored. Legumin is the main storage protein in chickpea seeds. Treatment of legumin with alcalase yielded a hydrolysate that inhibited the angiotensin I-converting enzyme with an IC 50 of 0.18 mg/ml. Fractionation of this hydrolysate by reverse phase chromatography afforded six inhibitory peptides with IC 50 values ranging from 0.011 to 0.021 mg/ml. All these peptides contain the amino acid methionine and are also rich in other hydrophobic amino acids. These results demonstrate that hydrolysates of chickpea legumin obtained by treatment with alcalase are a good source of peptides with angiotensin I-converting enzyme inhibitory activity.

Lupinus angustifolius protein isolates: chemical composition, functional properties and protein characterization

Abstract Two types of protein isolates were prepared from Lupinus angustifolius defatted flour by alkaline extraction, with (Isolate B) and without (Isolate A) sodium sulphite, and acid precipitation of proteins at the isoelectric point (IEP 4.3). Chemical composition, main functional properties and protein composition of L. angustifolius defatted flour and protein isolates were determined. Isolate A and B have 93.9 and 84.6% protein content, respectively, and had a balanced composition of essential amino acids, with respect to the FAO pattern except for lysine. The in vitro protein digestibility ranged between 86.3 and 93.9% for isolate A and B, respectively.

Differential presence of oleosins in oleogenic seed and mesocarp tissues in olive (Olea europaea) and avocado (Persea americana)

Abstract Olive drupes accumulate triacylglycerol (TAG) in the fleshy mesocarp of the fruit and also in the endosperm and embryo tissue of their seeds. Ultrastructural analysis has shown that, whereas the TAG in the seed tissues is stored in small, relatively regular oil bodies with diameters in the region of 0.5–2.0 μm, it is present in large, irregular oil bodies of 10–20 μm in the mesocarp. The fatty acid profiles of the TAG in oil bodies isolated from seed and mesocarp tissues are very similar, but oil bodies from these tissues differ dramatically in their protein content. Oil bodies from olive seed endosperm and embryo tissues contain about 10% (w/w) protein, whereas no significant protein was detected in oil bodies from mesocarp tissue of olive or avocado. Major polypeptides of 22 kDa and 50 kDa were purified from olive seed oil bodies and antibodies were raised against them. The 22-kDa oil-body protein was demonstrated to be an oleosin, based on its exclusive localisation on the surface of oil bodies of mature seed tissues, as shown by immunogold electron microscopy. It is concluded that oleosins, such as the 22-kDa polypeptide in olive, are present in the long-term storage oil bodies from the embryo and endosperm tissues of the seed and are absent from oil bodies of the mesocarp.

Protein quality of chickpea (Cicer arietinum L.) protein hydrolysates

Abstract Chickpea protein isolate (CPI) was used as the starting material in the production of chickpea protein hydrolysates (CPHs). To obtain a highly extensive hydrolysate with a degree of hydrolysis higher than 50%, a sequential utilisation of endoprotease (Alcalase) and exoprotease (Flavourzyme) was necessary. Molecular weight patterns of CPHs were determined by gel filtration chromatography. As a result of the enzymatic activity, differences in the chromatographic pattern of CPHs were observed. Although significant ( P ⩽0.05) decreases of Phe and Arg were observed after hydrolysis, adequate amounts of essential amino acids in relation to the reference pattern of FAO (FAO/WHO/ONU, 1985. Energy and requirements. Technical report series No. 724. Geneva) were found. In vitro protein digestibility of CPHs (95%) were similar to that of the starting material (CPI), and TIA was not detected in any case. A high increase of solubility in CPHs, with respect to CPI, was observed, one CPH being totally soluble over a wide pH range (2–10) when the enzymes were added sequentially. Due to their high protein quality and solubility, CPHs might be considered as potential ingredients in the food industry.

Effect of cooking on protein quality of chickpea (Cicer arietinum) seeds

Amino acid composition and in vitro protein digestibility of cooked chickpea were determined and compared to raw chickpea seeds. Heat treatment produced a decrease of methionine, cysteine, lysine, arginine, tyrosine and leucine, the highest reductions being in cysteine (15%) and lysine (13.2%). Protein content declined by 3.4% and in vitro protein digestibility improved significantly from 71.8 to 83.5% after cooking. The decrease of lysine was higher in the cooked chickpea seeds than in the heated protein fractions, globulins and albumins. The structural modification in globulins during heat treatment seems to be the reason for the increase in protein digestibility, although the activity of proteolytic inhibitors in the albumin fraction was not reduced. Results suggest that appropriate heat treatment may improve the bioavailability of chickpea proteins.

Factors affecting the in vitro protein digestibility of chickpea albumins

In vitro protein digestibility (IVPD) of chickpea albumins and its possible relationship to their structure and the presence of trypsin inhibitor activity (TIA) have been studied. Trypsin digestion of the albumin fraction under non-reducing conditions was incomplete, while the reduction of inter- and intramolecular disulphide bonds caused an improvement in the accessibility of sites susceptible to trypsin digestion. Trypsin inhibitor activity in the chickpea albumin fraction was dependent upon both temperature and heating time. Although heating the albumin fraction at 100 °C for 30 min reduced the TIA by more than 50% with respect to the initial activity, an important TIA rate was attributable to heat-resistant trypsin inhibitor. The TIA decrease was not related to an increase in the rate of IVPD. However, we observed a significant (P ≤ 0.05) increment in IVPD in the presence of β-ME, confirming the essential role of disulphide bonds in stabilising the protein structure of the albumin fraction. © 2000 Society of Chemical Industry

Performance evaluation of a mesophilic anaerobic fluidized-bed reactor treating wastewater derived from the production of proteins from extracted sunflower flour.

A study of the anaerobic digestion of wastewater derived from the production of protein isolates from extracted sunflower flour was carried out in a laboratory-scale, mesophilic (35 degrees C) fluidized-bed reactor with saponite as bacterial support. Chemical oxygen demand (COD) removal efficiencies in the range of 98.3-80.0% were achieved in the reactor at organic loading rates (OLR) of between 0.6 and 9.3 g COD/I d, hydraulic retention times (HRT) of between 20.0 and 1.1 d and average feed COD concentration of 10.6 g/l. Eighty percent of feed COD could be removed up to OLR of 9.3 g COD/l d. The yield coefficient of methane production was 0.33 l of methane (at STP) per gram of COD removed and was virtually independent of the OLR applied. Because the buffering capacity of the experimental system was maintained at favorable levels with excess total alkalinity present at all loadings, the rate of methanogenesis was not affected by loading. The experimental data indicated that a total alkalinity in the range of 2,000-2,460 mg/l as CaCO3 was sufficient to prevent the pH from dropping to below 7.0 for OLR of up to 9.3 g COD/l d. The volatile fatty acid (VFA) levels and the VFA/alkalinity ratio were lower than the suggested limits for digester failure (0.3-0.4) for OLR and HRT up to 9.3 g COD/l d and 1.1 d, respectively. For a HRT of 0.87 d (OLR of 12.1 g COD/l d) the start of acidification was observed in the reactor.

Chemical composition of extracted dried olive pomaces containing two and three phases

Abstract The chemical composition of extracted dried olive pomaces, obtained from extraction of systems containing two and three phases, was similar. The main component was fibre, with values above 70% in both systems. Nitrogen values and extractability was low for both systems, although in vitro protein digestibility was high (75–80%). Amino acid composition was balanced except for lysine. The isoelectric point was low, centred around pH 2.0. Soluble sugars and organic acids contents were similar as well as fatty acid composition of the extracted oil from olive pomace. Therefore, an oil extraction of a system of two phases is advisable as environmental problems could be reduced with the elimination of vegetation water, and similar applications could be carried out with both types after drying.

Effect of processing on water absorption and softening kinetics in chickpea (Cicer arietinum L) seeds

The processing effect on the physical properties of chickpea seeds (kabuli type cv Athenas) is reported. Soaking of chickpea seeds in different solutions (distilled water, 0·5% NaHCO3 and 0·5% CaCl2) is characterised by a rapid water absorption followed by a decrease in the hydration rate to saturation point. An improvement in chickpea softening rate and water absorption during cooking, with previous 12 h soaking in 0·5% NaHCO3, was observed. The presence of Ca2+ ions delayed the softening process in chickpea seeds. Physicochemical changes associated to the soaking and cooking process necessary for reducing cooking time are discussed. The texturometer method was estimated as a suitable objective method for the evaluation of the cooking degree in chickpea seeds.