Chemical characterization and functional properties of a potato protein concentrate prepared by large-scale expanded bed adsorption chromatography

Native potato proteins consisting mainly of patatin and protease inhibitors were isolated from industrial potato fruit water by expanded bed adsorption (EBA) chromatography. The EBA-refined proteins were dried by different methods and the effect of drying-conditions on solubility, extent of denaturation, rheology and emulsifying properties was investigated. Drying methods include spray drying at varying outlet temperatures, vacuum freeze drying, fluid-bed and atmospherical freeze drying. Solubilities measured in the range pH 4-6 showed that the higher solubility was at pH 6 of around 65%, except for spray drying using an outlet temperature of 165 °C, which showed low solubility for all pH values. Spray drying at 90 °C and atmospheric freeze-drying emerged as the least deleterious methods with respect to retaining esterase and protease inhibitor activities, comparable to the vacuum freeze drying. The values obtained for the complex modulus suggest that potato protein is not a good gel former even when the protein was vacuum freeze dried. Emulsions prepared with xanthan as stabilizer were more stable at pH 6 compared to pH 4 judged from oil particle sizes. This study showed that potato proteins obtained under gentle isolation and drying conditions will provide interesting functional properties for potential application in food systems.     

Functional properties of protein concentrates and isolates produced from cashew (Anacardium occidentale L.) nut

Protein isolates and concentrates were obtained from defatted cashew nut powder by two methods: alkaline extraction-isoelectric precipitation (IP) and alkaline extraction-methanol precipitation (MP). The functional properties of cashew nut protein isolates, concentrates and powder were significantly different (p < 0.05). Cashew nut protein isolate (CNPI) had higher water and oil absorption capacities (2.20 ml/g and 4.42 ml/g, respectively), emulsifying stability index (447%), foam capacity and stability (45% and 55%, respectively), and least gelation capacity (13.5%) than cashew nut protein concentrate (CNPC), which was also higher than that of defatted cashew nut powder (DCNP). However, emulsifying activity index (12.45%) and bulk density (0.31) of CNPI were lower than that of CNPC, which were also lower than that of DCNP. The water solubility of CNPI (95%) and CNPC (95%) was not significantly different (p > 0.05) among the samples, but was significantly different (p < 0.05) from that of DCNP (75%). The CNPI, CNPC and DCNP showed decreasing solubility with decreasing pH, with the minimum solubility being observed at a pH range of 4.0–4.5, confirming the isoelectric point of cashew proteins. However, higher water solubility, emulsifying activity, and foaming property were observed at an alkaline pH than at an acidic pH in all samples.     

Influence of oxidative browning inhibitors and isolation techniques on sweet potato protein recovery and composition

Effects of oxidative browning inhibitors on sweet potato protein (SPP) recovery and quality were studied. Oxidative browning inhibitors successfully decreased sweet potato oxidative browning, but reduced both SPP extractability and recovery. Ultrafiltration/diafiltration processed sweet potato (UDSP) protein (at pH 4, 6 and 7) showed significantly (p < 0.05) higher yield, purity, solubility, thermal stability and amino acid constituents than that of isoelectrically precipitated sweet potato (IPSP) protein (at pH 4). The yield of UDSP proteins was more than twice that of IPSP protein. Denaturation temperature (T_d), enthalpy change (ΔH) and solubility (at pH 3 and 8) of UDSP proteins were in the ranges 82.89–90.29 °C, 6.34–11.35 (J/g) and 71.4–94.2%, respectively, while that of IPSP protein were 85.27 °C, 2.35 (J/g) 31.2% and 55.5%, respectively. Ratio of SPP essential amino acid to the total amino acid ratio ranged from 0.49 to 0.51. SPP in vitro digestibility and digestibility-corrected amino acid score (PDCAAS) ranged 70–80.7% and 44.79–51.08%, respectively.     

The amino acid composition,solubility and emulsifying properties of sweet potato protein

A protein was purified from the high-protein type sweet potato variety 55-2 available in China. The amino acid composition, solubility and emulsifying properties of the sweet potato protein (SPP) were studied. The SPP was rich in aspartic acid (18.5%) and glutamic acid (9.30%) while essential acid amino acids made up approximately 40.7% of the SPP. The SPP was highly soluble in distilled water over a wide range of pH. However, solubility of the SPP in 1.0 M NaCl and 1.0 M CaCl₂ solutions was low especially at pH below the pI of the SPP. The SPP in CaCl₂ demonstrated emulsifying activity index (EAI) and emulsion stability index (ESI) many folds higher than those in distilled water and NaCl solution (P < 0.05).     

Some physicochemical and functional properties of alfalfa soluble leaf proteins

Important physicochemical and functional properties of soluble leaf proteins (SLPs) from alfalfa herbage are presented. Subunits molecular weight (MW) distribution, denaturation temperature, and functional properties like, emulsification, foaming, and solubility are discussed. SLP concentrates were prepared by acid precipitation, and ultrafiltration of clarified alfalfa juice. The MW of major soluble protein component ribulose 1,5, bisphosphate carboxylase/oxygenase was estimated to be around 490 kDa. Denaturation temperature of soluble proteins was observed to be around 70-75 °C. Most of the functional properties were affected by concentrate preparation. Acid-precipitated SLP concentrate showed lowest emulsifying properties and nitrogen solubility. Heat stability of emulsions was good. Foam overrun for SLP concentrate depended on pH and was stable around protein's isoelectric point. Stress relaxation tests on 7/100 g SLP gels indicated that they were softer gels and relaxed faster compared to 13/100 g WPI gels. SLP preparations showed encouraging functional properties.     

Rheological properties of soy protein hydrolysates obtained from limited enzymatic hydrolysis

Soy protein products hexane-defatted soy flour, extruded-expelled soy flour, soy protein concentrate and soy protein isolate, were modified by using the enzyme bromelain to 2% and 4% degrees of hydrolysis (DH). Peptide profiles, water solubility, and rheological properties including dynamic shear, large deformation, and apparent viscosities of resulting hydrolysates were determined. Protein subunits profiles for the hydrolysed isolates and concentrates were extensively altered by the treatment while only minor changes were observed for the hydrolysed flours. Water solubility profiles of all hydrolysates in the pH range of 3.0-7.0 were enhanced by hydrolysis. For the unhydrolysed controls, the isolate had the highest storage modulus (G′), followed by the concentrate, the extruded-expelled flour and the hexane-defatted flour. The hydrolysates retained some of their gelling ability even though the losses in storage modulus (G′) were substantial. After heating step to 95 °C, the G′ values of all substrates at 25 °C decreased with increase in DH. Texture profile analyses of the soy protein gels were also lower in hardness after hydrolysis. The Power Law model provided excellent fit to hydrolysate dispersions flow (R²>0.99). Hydrolysis decreased the consistency coefficients of dispersion and increased flow behavior index resulting in thinner dispersions. These results suggest that limited protease hydrolysis of various soy protein meals with bromelain produce soy protein ingredients with modified rheological properties.     

Effect of pH on phosphorylation of potato protein isolate

Potato protein isolate (PPI) was phosphorylated with sodium trimetaphosphate (STMP) at ambient temperature and various reaction pH (5.2, 6.2, 8.0 and 10.5) to improve the functional properties without impairing the nutritional availability. Changes in chemical composition (total and coagulable protein content, ash and minerals content and amino acid composition), functional properties (protein solubility index, emulsifying activity and foaming capacity, water and oil absorption capacity) and phosphorus were determined. The chemical composition and functional properties of phosphorylated potato protein isolate (PP-PPI) were significantly different (p < 0.05). The PP-PPI at pH 5.2 was characterised by the highest content of all amino acids, whereas, PP-PPI under alkaline conditions (pH 10.5) caused decrease in these compounds. PP-PPI at pH 8.0 had the highest oil absorption capacity, emulsion activity and foam capacity, whereas, PP-PPI at pH 10.5 had the highest WAC.     

Physico-chemical, amino acid composition, functional and antioxidant properties of roe protein concentrates obtained from Channa striatus and Lates calcarifer

Roe protein concentrates prepared from Channa striatus (CRPC) and Lates calcarifer (LRPC) were investigated for physico-chemical characteristics, amino acid composition, functional properties and antioxidant activity. Channa and Lates roes yielded 20.7% and 22.5% of protein concentrates possessing 90.2% and 82.5% protein, respectively. Major differences were not observed in each of the amino acids except leucine in CRPC and LRPC. The solubility of protein was 3.93-54.6% and 1.6-55.5% over a pH range of 2-12 in CRPC and LRPC, respectively. Water absorption, oil absorption, foam capacity, stability and emulsifying capacity were found to be higher in CRPC than in LRPC. Antioxidant activity determined by the radical scavenging activity and ferric reducing power was higher in CRPC. SDS-PAGE of both roe protein concentrates showed protein bands of 170, 95 and 55 kDa. Moisture sorption isotherms of protein concentrates indicated their hygroscopic nature.     

Changes in nutritional value of potato proteins during the preparation of potato protein concentrate from tuber sap

Nutritional value of potato proteins and its changes during the preparation of potato protein concentrates was studied. Proteins were coagulated by a heat treatment (80-85°C) at pH 4.5, the coagulate was washed with water and spray- or drum-dried. Both the chemical analyses (amino acid content, available lysine and trypsin inhibitor activity) and the biological evaluation (true N digestibility, biological value, net protein utilization) showed that no changes (with the exception of slight fluctuations during the drum drying) occurred during the technological procedure which could adversely affect the nutritional value of proteins. Protein of the products obtained had a high nutritional value, comparable with that of the soy protein concentrate.     

Low temperature dry extrusion and high-pressure processing prior to enzyme-assisted aqueous extraction of full fat soybean flakes

Oil, protein and solid extraction yields obtained during aqueous extraction processing (AEP) of full fat soybean flakes (FFSF), FFSF extruded at a die temperature of 100 °C and FFSF pressurised at 200 and 500 MPa for 15 min at 25 °C, were compared to those obtained during enzyme-assisted aqueous extraction processing (EAEP) using 0.5% of protease Protex 7L. Without enzyme addition, pretreatment of the FFSF with extrusion and 500 MPa increased and decreased, respectively, the oil extraction yield while protein extraction yield was significantly decreased after both treatments. The best treatment in terms of oil and protein recovery was EAEP of extruded flakes with 90% and 82% of oil and protein extraction yield, respectively, and 17% of free oil. Addition of protease during extraction significantly decreased the yield of isolated soy protein (ISP) due to an increased solubility of the proteins at pH 4.5. ISP from extruded EAEP had higher solubility at pH 7.0 and better functionality. The DSC results, combined with the protein extraction yields, showed that a proportion of the proteins became insoluble after extrusion and 500 MPa treatment, while only those extracted from 500 MPa FFSF had a reduced native state.     

Preparation and characterisation of protein concentrates from defatted kenaf seed

Two kenaf varieties QP3 and V36 were used to obtain protein concentrates. Proximate analysis, foaming, water and oil absorption properties were studied. Significant (P < 0.05) differences were observed among the two varieties only in their content in oil and carbohydrates. The protein concentrate yield was 13.04% and 10.56%, respectively. The two varieties showed significantly different (P < 0.05) water and oil absorption capacities. QP3 showed higher foaming capacity than did V38, and it was increased with increasing salt and sugar concentration. Albumin was the main fraction representing 59.6% and 66.1% in QP3 and V36 varieties, respectively, followed by globulin, which represented 22.6% and 19.1%, respectively. The ratios of albumin, globulin, glutelin and prolamin were significantly different. Based on the data obtained from sodium dodecyl sulphate polyacrylamide gel electrophoresis, the main kenaf seed proteins present in the concentrates were five proteins with molecular weights ranging from 10 to 66 kDa. From differential scanning calorimetry data, QP3 and V36 protein concentrates had similar denaturation temperatures (82.6 and 81.8 °C, respectively).     

Comparative study of potato protein concentrates extracted using ammonium sulfate and isoelectric precipitation

In this study, effects of NaCl concentrations (0.0, 0.2, 0.4, 0.6, 0.8, and 1.0 M) and pH (3.0, 5.0, 7.0, and 8.0) on the physico-chemical and functional properties of potato protein concentrates extracted from potato fruit juice (PFJ) using ammonium sulfate precipitation (ASP) and isoelectric precipitation (IEP) were investigated. The total polyphenol content of potato protein concentrates extracted by IEP (IEPP) was 2.5 times of that of potato protein concentrates extracted by ASP (ASPP), which resulted in the color of IEPP darker than that of ASPP. More protein fractions (74, 62, and 35 kDa) were found in IEPP compared to ASPP. ASPP exhibited higher solubility than IEPP. The emulsifying properties of ASPP and IEPP increased along with the increasing NaCl concentration. ASPP and IEPP showed the lowest emulsifying properties and foaming ability at pH 5.0. While the foaming stability of ASPP and IEPP achieved the maximum and minimum at pH 5.0, respectively. Two endothermic peaks were observed in ASPP at pH 3.0, 8.0, and higher NaCl concentration (≥0.6 M), while more than two endothermic peaks were observed in IEPP at all NaCl concentrations (0.2–1.0 M) and pH values (3.0, 5.0, 7.0, and 8.0). The glutamic acid concentration of ASPP and aspartic acid concentration of IEPP were the highest, while histidine was the lowest according to the amino acid profile of both ASPP and IEPP. In terms of an essential amino acid index with respect to a reference protein of FAO/WHO, the nutritional values of IEPP were higher than those of ASPP.     

The acylated protein derivatives of Canavalia ensiformis (jack bean): A study of functional characteristics

Protein concentrate was prepared from jack bean (JNP) and it was modified by acylation using acetic (JAP) and succinic anhydrides (JSP). Proximate analyses revealed that moisture and ash content increased following acetylation and succinylation, while both acetylation and succinylation reduced percentage crude fat and protein. Acetylation and succinylation reduced protein solubility in the acidic pH range below the isoelectric point (4.5) of the protein concentrate but improved the solubility of the unmodified protein concentrate at the isoelectric point and pH range alkaline to the isoelectric point. Both acetylation and succinylation increased the water absorption capacity of unmodified protein concentrates at all levels of ionic strength investigated (0.1-1.0 mol/l). Acetylation improved oil absorption capacity whereas the tendency to absorb oil reduced after succinylation. Maximal emulsifying activity of native and modified proteins were obtained at pH 10. Emulsion stability of acylated proteins was higher than those of native proteins in the range of pH 4-10 but lower when the pH was 2. Foam capacity and stability of both native and modified proteins increased with increase in protein concentration. Foam capacity of modified proteins increased progressively with increase in pH from 2 to 10. Also, acylated protein derivatives had improved foam capacity over the native protein except at pH 2. Gelation capacity of both native and modified proteins was maximal at the region of isoelectric point.     

Two-stage foam separation technology for recovering potato protein from potato processing wastewater using the column with the spiral internal component

For recovering potato protein from potato processing wastewater, the effects of temperature, pH, volumetric airflow rate, liquid loading volume and sparging time on the foam separation performances were investigated using the column with the spiral internal component (SIC). A two-stage foam separation technology was designed to improve both the enrichment ratio and recovery percentage of potato protein. The results showed that the SIC and specially the increase of temperature were effective for improving the enrichment ratio of potato protein. A best enrichment ratio of potato protein of 4.69 was obtained under the optimal conditions of temperature 45 °C, pH 7, volumetric airflow rate 100 mL/min, liquid loading volume 300 mL and sparging time 90 min. The total recovery percentage of potato protein was as high as 73.4% by using the two-stage foam separation technology. So the two-stage technology was effective for the protein recovery from potato processing wastewater.     

Proteolysis of noncollagenous proteins in sea cucumber, Stichopus japonicus, body wall: Characterisation and the effects of cysteine protease inhibitors

Proteolysis of noncollagenous proteins in sea cucumber, Stichopus Japonicus, body wall (sjBW) was investigated. The proteins removed from sjBW by SDS and urea extraction were mainly noncollagenous proteins with molecular weights about 200 kDa (Band I) and 44 kDa (Band II), respectively. Band I and Band II were identified as major yolk protein (MYP) and actin, respectively, from holothurian species by liquid chromatography–mass spectrometry (LC–MS/MS) with significant scores. Based on TCA-soluble oligopeptide assay, the optimum proteolysis condition of noncollagenous proteins was at 46.3 °C and pH 6.1, by response surface methodology. The proteolysis of MYP, and actin, was partially inhibited by cysteine protease inhibitors, including Trans-epoxysuccinyl-l-leucyl-amido (4-guanidino) butane (E-64), iodoacetic acid, antipain and whey protein concentrate. These results suggest that cysteine proteases are partially involved in the proteolysis of noncollagenous proteins in body wall of sea cucumber, S. japonicus.     

Antioxidant and emulsifying properties of potato protein hydrolysate in soybean oil-in-water emulsions

The efficacy of a previously developed antioxidative potato protein hydrolysate (PPH) for the stabilisation of oil droplets and inhibition of lipid oxidation in soybean oil-in-water (O/W) emulsions was investigated. Emulsions (10% lipid, pH 7.0) with PPH-coated oil droplets were less stable than those produced with Tween 20 (P < 0.05). However, the presence of PPH, whether added before or after homogenisation with Tween 20, retarded emulsion oxidation, showing reduced formation of peroxides up to 53.4% and malonaldehyde-equivalent substances up to 70.8% after 7-d storage at 37 °C (P < 0.05), when compared with PPH-free emulsions. In the emulsions stabilised by PPH + Tween 20, 8–15% of PPH was distributed at the interface. Adjustment of the pH from 3 to 7 markedly increased ζ-potential of such emulsions (P < 0.05). Inhibition of lipid oxidation by PPH in soybean O/W emulsions can be attributed to both chemical and physical (shielding) actions.     

Effects of supplementing concentrates differing in carbohydrate composition in veal calf diets: I. Animal performance and rumen fermentation characteristics

The aim of this experiment was to examine the effects of concentrates in feed, differing in carbohydrate source, on the growth performance and rumen fermentation characteristics of veal calves. For this purpose, 160 Holstein Friesian × Dutch Friesian crossbred male calves were used in a complete randomized block design with a 5 × 2 factorial arrangement. Dietary treatments consisted of 1) milk replacer control, 2) pectin-based concentrate, 3) neutral detergent fiber-based concentrate, 4) starch-based concentrate, and 5) mixed concentrate (equal amounts of concentrates of treatments 2, 3, and 4). Concentrate diets were provided as pellets in addition to a commercial milk replacer. Calves were euthanized either at the end of 8 or 12 wk of age. The overall dry matter intake of the concentrate diets varied between 0.37 and 0.52 kg/d. Among the concentrate diets, the dry matter intake was lower in the starch diet (0.37 kg/d of dry matter) and differed between the NDF and pectin diets. The average daily gain for all the dietary treatments varied between 0.70 and 0.78 kg/d. The mixed- and NDF-fed calves had an increased average daily gain (0.78 and 0.77 kg/d, respectively) compared with the starch- and pectin-fed calves (0.70 and 0.71 kg/d, respectively). Rumen fermentation in the calves fed concentrates was characterized by a low pH (4.9 to 5.2), volatile fatty acid concentrations between 100 and 121 mmol/L, and high concentrations of reducing sugars (33 to 66 g/kg of dry matter). The volatile fatty acid concentrations of calves fed concentrates were higher than those of the control calves. All concentrate treatments showed a low acetate-to-propionate ratio in rumen fluid (between 1.3 and 1.9). Among the concentrates, the NDF diet had the highest (55.5%) and starch the lowest (45.5%) molar proportions of acetate. Calves fed the mixed, pectin, and starch diets had significantly higher molar proportions of butyrate (13.1 to 15.8%) than the NDF- and control-fed groups (9.9 and 9.6%, respectively). Calves fed the control diet had a higher lactate concentration (21 mmol/L) than the concentrate-fed calves (between 5 and 11 mmol/L). With the exception of the NDF diet, polysaccharide-degrading enzyme activities in the rumen contents generally showed an adaptation of the microorganisms to the carbohydrate source in the diet. The mixed diet exhibited the least variation in rumen polysaccharide-degrading enzyme activities among the enzymes systems tested. Results indicated that the carbohydrate source can influence intake, growth rate, and rumen fermentation in young veal calves.     

Effect of alternative processes on the yield and physicochemical characterization of protein concentrates from Amaranthus cruentus

Three different processes for the preparation of amaranth protein concentrates (APCs) were investigated with respect to the yield and physicochemical characteristics. The first was the conventional process for isolating protein (standard process), the second included an acid washing step prior to protein extraction (acid washing process) and the third included heating (50 °C) during the alkaline extraction step (thermal process). The protein yields were 17.8 and 25.6% for the acid washing and thermal processes, respectively. The concentrates were analyzed by SDS-PAGE, free sulfhydryl groups (SH), differential scanning calorimetry (DSC), size-exclusion high performance liquid chromatography (SE-HPLC), solubility in water and in 0.05 mol L⁻¹ NaCl at pH 3.0, 4.5 and 7.0, phenolic compounds content and color parameters. The results indicated that the acid washing process had positive effects on the composition, color parameters, protein solubility and thermal stability of the concentrates. The thermal process also brought about positive effects on the characteristics of the proteins and color parameters although it negatively affected solubility due to the formation of high molar mass aggregates. The conventional process, when compared with the thermal and acid washing processes, adversely affected the properties evaluated.     

Functional properties of fish protein hydrolysates from Pacific whiting(Merluccius productus) muscle produced by a commercial protease

Pacific whiting (Merluccius productus) muscle was used to produce hydrolysates with 10%, 15% and 20% degree of hydrolysis (DH) using the commercial protease Alcalase^® and were characterized at pH 4.0, 7.0 and 10 according their solubility, emulsifying and foaming properties. Protein recovered in soluble fractions increased proportionally with the hydrolytic process, yielded 48.6 ± 1.9, 58.6 ± 4.1 and 67.8 ± 1.4 of total protein after 10%, 15% and 20% DH, respectively. Freeze-dried hydrolysates presented almost 100% solubility (p > 0.05) at the different pHs evaluated. Emulsifying properties (EC, EAI and ESI) were not affected by DH as most samples showed similar (p > 0.05) results. Higher EC (p ? 0.05) than sodium caseinate, used as control, were obtained at pH 4 for most hydrolysates. Hydrolysates showed very low foaming capacity not affected by pH; but foam stability was equal or even better (p > 0.05) than bovine serum albumin (BSA), except at pH 4.0. Results suggest that hydrolysates from Pacific whiting muscle can be produced with similar or better functional properties than the food ingredients used as standards.     

Manufacture of bioactive peptide-rich concentrates from Whey: Characterization of pilot process

This work was focused on the manufacture, at pilot scale, of cow whey protein and peptide concentrates, using selective filtration techniques—associated with hydrolysis brought about by proteolytic enzymes from Cynara cardunculus aqueous extracts, using as (optimal) conditions an enzyme/substrate ratio of 1.6% v/v, a pH of 5.2, a temperature of 55 °C and an incubation time of 7 h. The profiles of proteins and peptides were assessed by liquid chromatography and electrophoresis; ca. 87% of α-lactalbumin was hydrolyzed, but essentially no degradation of β-lactoglobulin (β-Lg) was observed. A bioactive peptide concentrate, its fraction below 3 kDa and a β-Lg-rich fraction were obtained as final products, containing ca. 73, 43 and 91% w/w protein (on a total solid mass basis). All these fractions were low in lactose and salt, and their microbial loads were reduced. Said fractions are high added-value products, so they can be used as nutritional and functional ingredients—thus yielding an economically viable alternative for upgrade of whey.