Coagulated Protein For Human Food Patent Application (2025)

U.S. patent application number 16/077930 was filed with the patent office on 2019-03-21 for coagulated protein for human food. The applicant listed for this patent is COOPERATIE AVEBE U.A.. Invention is credited to Hendrik Huttinga, Marc Christiaan Laus, Marcus Johannes Vorage.

COAGULATED PROTEIN FOR HUMAN FOOD

Abstract

The invention pertains to a coagulated root- or tuber proteinproduct which is not horny. Such products are characterized by asmall particle size, a low density and little color, which makesthem suitable for human food applications. The invention furtherpertains to a process for obtaining non-horny root- or tubercoagulated protein, and to use of these products in human foodapplications.

Foreign Application Data

Claims

1. A coagulated root or tuber protein powder having a glycoalkaloidcontent of below 100 mg/kg dry weight, wherein the d-10 is lessthan 30 .mu.m, the d-50 is less than 75 .mu.m, and the d-90 is lessthan 250 .mu.m, expressed on a dry product, and wherein the totalcontent of glucose, fructose and sucrose is less than 0.5 g/kg dryweight.

2. A coagulated root or tuber protein powder according to claim 1,wherein the bulk density of the protein powder is less than 475g/l.

3. A coagulated root or tuber protein powder according to claim 1,wherein the color of the protein powder by reflection is>0.50.

4. A coagulated root or tuber protein product according to claim 1,wherein the protein content before neutralization is at least 85wt. %, as determined by Kjeldahl nitrogen.

5. A coagulated root or tuber protein product as defined in claim1, obtainable by a method comprising a) subjecting the root ortuber fruit juice to a coagulation step to obtain coagulatedprotein; b) collecting the coagulated protein; c) washing thecoagulated protein with washing water having a conductivity ofbelow 1 mS/cm to obtain used washing water and washed coagulatedprotein; and d) drying the washed coagulated protein, whereinwashing is continued until the used washing water has aconductivity of less than 2 mS/cm.

6. A method to obtain a coagulated root or tuber protein powderfrom a root or tuber fruit juice, comprising a) subjecting the rootor tuber fruit juice to a coagulation step to obtain coagulatedprotein; b) collecting the coagulated protein; c) washing thecoagulated protein with washing water having a conductivity ofbelow 1 mS/cm to obtain used washing water and washed coagulatedprotein; and d) drying the washed coagulated protein, whereinwashing is continued until the used washing water has aconductivity of less than 2 mS/cm.

7. A method according to claim 6, wherein washing is continueduntil the used washing water has a conductivity of less than 1mS/cm.

8. A method according to claim 6, wherein the washing is continueduntil the content of glucose, fructose and sucrose in the usedwashing water is less than 0.54 mgt.

9. A method according to claim 6, wherein the method furthercomprises a step of neutralizing the coagulated protein to a pH of6.5-7.

10. A method according to claim 6, wherein the method furthercomprises a glycoalkaloid extraction procedure.

11. A method according to claim 6, wherein the coagulated root ortuber protein powder is subsequently fractionated into at least afirst fraction and a second fraction.

12. A method according to claim 11, wherein the first fraction hasa d-50 of at most 35 .mu.m.

13. A method according to claim 11, wherein the second fraction hasa d-50 of 42-69 .mu.m.

14. Use of a coagulated root or tuber protein as defined in claim 1in human food applications.

15. Use according to claim 14, wherein the food is a nutritiousdrink.

Description

[0001] The invention pertains to coagulated root or tuber proteinproducts, which are suitable for human food applications, and to aprocess to obtain such products, as well as use thereof in humanfood.

[0002] Coagulated protein products are known, and comprise forinstance protein products obtained by acid or thermal coagulation.Coagulation of protein results in protein denaturation, so that thedenatured protein is rendered insoluble, and coagulates to form asolid mass which may be isolated by for instance decantation,filtration or centrifugation.

[0003] A disadvantage of known coagulated protein products is thatthey are not suitable for human food applications. Despite the factthat the amino acid composition of root or tuber protein productsis often favorable, known coagulated protein products are hard andsolid (also called "horny"), and have a typical large particle sizeof d10 of 29 .mu.m, d50 of 102 .mu.m and d90 of 512 .mu.m (dryparticle size), which makes their organoleptic properties such astaste and mouthfeel unsuitable for human food applications. Oncecoagulated protein has turned horny, this process cannot bereversed. In addition, known products are often colored to such anextent that they cannot be used in human food.

[0004] In the present invention, we disclose for the first time aprocess to obtain a coagulated protein product which is not horny.Because the hard and solid character of the coagulated proteinparticles can be avoided, the product can be applied in human foodapplications, which benefit from the advantageous nutritionalproperties.

FIGURES

[0005] FIG. 1: microscope analysis of food-grade coagulated proteinproduct according to the invention (FIG. 1a) and of conventionalcoagulated protein product (FIG. 1b). Scale bar in both pictures0.5 mm.

[0006] FIG. 2: color of washing water; from left to right: initialwashings, acid was, water wash until conductivity of 1 mS/cm.

[0007] FIG. 3: pH, conductivity and total glycoalkaloid content infiltrate FIG. 4: Influence of washing on particle size distributionof dry potato protein. Blue line=sample 2, red line=sample 5, greenline=sample 4.

[0008] FIG. 5: Sediment layer formation in time of the samplesproduced in example 3 after 1, 2, 4, 6 8 and 10 minutes. Arrowsindicate the sediment layer.

[0009] FIG. 6: Particle size ratio between dry (Sympatec) and wet(Malvern) particle size analysis techniques.

DETAILED DESCRIPTION

[0010] The present invention discloses a coagulated root or tuberprotein product, which is not horny and which can be used in humanfood applications. The non-horny coagulated protein product ischaracterized by a small particle size, a low color, a low density,low off-taste and low level of residual sugars, relative to knowncoagulated root or tuber protein products.

[0011] It has been found that a non-horny protein product can beobtained by subjecting the coagulated protein product to extensivewashing. Surprisingly, it was discovered that formation of hornymaterial is due to a range of sticky components, which stick to theprotein even after washing. Upon drying, the protein coagulates dueto the presence of these sticky components, and forms hornymaterial. By extensive washing according to the invention, even thesticky components are removed, and a non-horny protein material canbe obtained. Non-horny material has the advantages described above,which makes it suitable for use in human food applications.

[0012] Coagulated protein products have lost all enzymaticfunctionality, and can be produced in large quantities in largescale installations in comparison with native protein products.Coagulated protein products are not soluble in water, whereasnative protein products generally have high solubility. As aresult, coagulated protein products and native protein productshave different application area's, and a coagulated protein productused in one application cannot be substituted for a native product,and vice versa. Therefore, the present coagulated protein productshould be compared with known coagulated protein products, and notwith native protein products.

[0013] The present invention discloses coagulated root or tuberprotein. Root or tuber in this context pertains to the species ofpotato (Solanum tuberosum or Irish potato, a seasonal crop grown intemperate zones all over the world); sweet potato (Ipomoea batatas,a seasonal crop grown in tropical and subtropical regions, usedmainly for human food); cassava (including Manihot esculenta, syn.M. utilissima, also called manioc, mandioca or yuca, and alsoincluding M. palmata, syn. M. dulcis, also called yuca dulce, whichare semi-permanent crops grown in tropical and subtropicalregions); yam (Dioscorea spp, widely grown throughout the tropicsas a starchy staple foodstuff); yautia (a group including severalplants grown mainly in the Caribbean, some with edible tubers andothers with edible stems, including Xanthosoma spp., also calledmalanga, new cocoyam, ocumo, and also including tannia (X.sagittifolium)); taro (Colocasia esculenta, a group of aroidscultivated for their edible starchy corms or underground stems,grown throughout the tropics for food, also called dasheen, eddoe,taro or old cocoyam); arracacha (Arracacoa xanthorrhiza); arrowroot(Maranta arundinacea); chufa (Cyperus esculentus); sago palm(Metroxylon, spp.); oca and ullucu (Oxalis tuberosa and Ullucustuberosus); yam bean and jicama (Pachyrxhizus erosus and P.angulatus); mashua (Tropaeolum tuberosum); Jerusalem artichoke(topinambur, Helianthus tuberosus).

[0014] Preferably, the root or tuber is a potato, sweet potato,cassava or yam, and more preferably the root or tuber is a potato(Solanum tuberosum).

[0015] Coagulated root or tuber protein pertains to any proteinfraction which can be obtained from root or tuber. That is,coagulated root or tuber protein may pertain to a coagulatedprotein product comprising substantially all protein present in aparticular root or tuber, but may also pertain to a fraction ofprotein present in that particular root or tuber, such as may occuron waste streams of root or tuber juice, where some protein hasalready been removed in a primary process. Preferably, thecoagulated protein product is a product comprising substantiallyall protein present in a waste stream obtained from starchisolation.

[0016] The coagulated protein product is characterized by a d-10 ofless than 30 .mu.m, preferably less than 28 .mu.m, more preferablyless than 24 .mu.m, more preferably less than 20 .mu.m. It isfurther characterized by a d-50 of less than 75 .mu.m, preferablyless than 65 .mu.m, even more preferably less than 55 .mu.m, and ad-90 of less than 250 .mu.m, preferably less than 200 .mu.m, morepreferably less than 150 .mu.m, as determined on a dry product.

[0017] The d-10, d-50 and d-90 are common parameters to expressparticle size distribution. The d-50 is the volume median particlesize, and indicates the diameter, in .mu.m, that splits thedistribution into two equal fractions, wherein half of the particlevolume has a diameter above the median diameter, and wherein halfof the particle volume has a diameter below the median diameter. Itcan also be referred to as Dv50.

[0018] Similarly, the d-10 indicates the diameter, in .mu.m, thatsplits the particle size distribution into two (volume) portions,wherein 10% of the particle volume has a diameter below the d-10,and wherein 90% of the particle volume has a diameter above thed-10.

[0019] The d-90 is defined in a similar manner, and indicates thediameter that splits the particle size distribution into two(volume) portions, wherein 90% of the particle volume has adiameter below the d-90, and wherein 10% of the particle volume hasa diameter above the d-90.

[0020] The (dry) particle size can be determined laser diffractionusing a Sympatec HELOS equipped with a RODOS dry dispenser with avibratory feeder. The RODOS dispersing line has an inner diameterof 4 mm. Particle sized is calculated by the integrated softwareusing the "fraunhofer" formula. Particles size reported here allrefer to the dry particle size.

[0021] Particle size can alternatively be determined by a "wet"method. In that case, the "wet" particle size can be converted to a"dry" particle size by division of the wet particle size using 1.3as conversion factor (FIG. 6).

[0022] The product is further characterized by a glycoalkaloidcontent of below 200 mg/kg, preferably below 150 mg/kg, morepreferably below 100 mg/kg, even more preferably below 50 mg/kg.Glycoalkaloid levels influence the taste of the potato proteinproduct. Bitter tasting potato varieties were reported to containglycoalkaloid levels exceeding 140 mg/kg fresh weight, while aburning perception in the mouth and throat was apparent with levelsabove 220 mg/kg. In addition, glycoalkaloids are known to bepoisonous, and their presence in consumption potatoes is restrictedby law. Therefore, the glycoalkaloid level is preferably low. Theglycoalkaloid content can be determined by the method of Alt andcoworkers (V. Alt, R. Steinhof, M. Lotz, R Ulber, C. Kasper, and TScheper--Optimization of Glycoalkaloid Analysis for Use inIndustrial Potato Fruit Juice Downstreaming--Eng. Life Sci. 2005,5, No. 6).

[0023] The protein product is further characterized by a lowvolumetric density of 475 gram per liter or lower, such as below400 gram/liter, preferably below 350 gram/liter, more preferablybelow 300 gram/liter.

[0024] The protein product is further characterized by a low color.Low color in this context is expressed as the reflected color,which can be determined by a Hunterlab Colorflex EZspectrophotometer as described below. The protein powder of theinvention is characterized by a reflection color of greater than0.50, preferably greater than 0.56, more preferably greater than0.58, even more preferably greater than 0.60, most preferablygreater than 0.62.

[0025] The protein product has preferably not been subjected to astep which actively reduces particle size by physical means, suchas in a homogenizer, a wet or dry mill, or a dryer with millingfunction.

[0026] The protein product can suitably be obtained by a methodcomprising

a) subjecting the root or tuber fruit juice to a coagulation stepto obtain coagulated protein; b) collecting the coagulated protein;c) washing the coagulated protein with washing water having aconductivity of below 1 mS/cm to obtain used washing water andwashed coagulated protein; and d) drying the washed coagulatedprotein, wherein washing is continued until the used washing waterhas a conductivity of less than 2 mS/cm.

[0027] It has been found that extensive washing removes many of thesticky components which have been found to be responsible for theformation of horny protein material upon drying. These stickycomponents include among others sugars, potassium, and variousorganic acids and amino acids, in particular sugars. Sugars in thiscontext are defined as the total of glucose, fructose and sucrose.A potato contains on average of 7.5 mg sugars/g potato. The totalamount of sticky components can be as high as 35-40 mg/g potato. Ithas been found that the sticky components tend to "stick" tocoagulated protein material, such that conventional washing doesnot sufficiently remove them, and a horny material is formed.

[0028] As a result, it is essential that root or tuber proteinafter coagulation is washed extensively prior to drying. When thecoagulated protein material is washed until the washing water hasreached a specific conductivity, this indicates that the stickycomponents are sufficiently removed so that the coagulated proteinmaterial does no longer form large horny lumps, but remains apowder with a small particle size, low color (high reflectioncolor) and low density and other advantages as defined above. Thespecific conductivity of the used washing water at which coagulatedprotein material does no longer form horny material is 2 mS/cm,preferably 1.5 mS/cm, even more preferably 1 mS/cm.

[0029] Washing to these levels ensures that the sticky components,importantly sugars, are removed to a sufficient degree so as toavoid formation of horny material. Alternatively therefore, washingmay be continued until the washing water contains less than 0.54mg/g sugars, preferably less than 0.4 mg/g, more preferably lessthan 0.3 mg/g, more preferably less than 0.2 mg/g. Sugars in thiscontext are defined as the total of glucose, fructose and sucrose.This results in a coagulated protein product which comprises lessthan 0.40 g/kg dry weight of sugars, preferably less than 0.35 g/kgdry weight. It has been found that these low amounts of sugarsmakes it possible to obtain a coagulated protein product which isnot horny.

[0030] The present method to obtain non-horny coagulated proteinmaterial starts with subjecting the root or tuber fruit juice to acoagulation step to obtain coagulated protein. The root or tuberjuice preferably has a protein content of 0.1-5 wt. %, morepreferably 1-2 wt. % but may be concentrated prior to coagulation,such as to a protein content of 3-20, preferably 5-15 wt. %.Concentration may be achieved in any known way, such as for exampleby ultrafiltration, diafiltration or freeze concentration.

[0031] Coagulated protein can be obtained by heat or acidcoagulation, preferably in water, or by subjecting the protein to asufficient quantity of a coagulating organic solvent orprecipitation aid, as is known in the art. These techniques or acombination thereof result in a suspension comprising coagulatedprotein.

[0032] Heat coagulation may be achieved by subjecting the protein,preferably in an aqueous environment, to heat, for a time longenough to coagulate the protein. This may be achieved by subjectingthe protein to a temperature of at least 70.degree. C., preferablyat least 80.degree. C., more preferably at least 90.degree. C. oreven to a temperature of 100.degree. C. or even more, for a periodof several minutes, preferably at least 30 minutes, more preferablyat least 1 hr, even more preferably at least 2 hrs, such as forinstance 30 min-5 hr or 1-4 hr. The higher the temperature, theshorter the time required for coagulation. In a preferredembodiment, coagulation is achieved at a temperature of100-110.degree. C., for a period of 1-60 seconds, for example at apH of 4.5-6.

[0033] Acid coagulation may be achieved by subjecting the protein,preferably in an aqueous environment, to a strong acid, such ashydrochloric acid, sulphuric acid, or weak (an) organic acids suchas phosphoric acid, citric acid or lactic acid. The pH in thecoagulating mixture is preferably from 0 to 6, preferably from 2-6.In some embodiments, protein is coagulated by a combination ofacid- and heat coagulation.

[0034] Coagulation may also be achieved by subjecting the proteinto a sufficient quantity of a coagulating organic solvent. Suchsolvents are known in the art. Suitable coagulating organicsolvents are for instance ethanol and propanol. Preferably, this isachieved by addition of the coagulating organic solvent to anaqueous environment comprising the protein. A sufficient quantityof the coagulating solvent can be at least 15 vol. % in water,preferably at least 20 vol. % in water, more preferably at least 40vol. % in water.

[0035] Coagulation may also be achieved by subjecting the proteinto a sufficient quantity of a coagulating agents. Suitablecoagulating agents are for instance metal salts (for exampleFeCl.sub.3, ZnCl.sub.2 or MnCl.sub.2. Suitable concentrations forusing metal salts are 1-80 mM, preferably 10-50 mM. Alternatively,coagulation may be achieved by carboxymethyl cellulose (CMC)complexation (CMC/protein weight ratio 0.05-0.2, preferably0.08-1.4). Preferably, this is achieved by adding the coagulatingagent to an aqueous environment comprising the protein.

[0036] After the coagulation step, the coagulated protein iscollected. This can be achieved by known methods, such asfiltration, centrifugation or sedimentation.

[0037] Filtration may be achieved by passing the coagulated proteinover a filter or membrane of 5-100 .mu.m, preferably 10-30.mu.m.

[0038] Centrifugation by means of a centrifuge, decanter orhydrocyclone separator may be achieved by subjecting the suspensioncomprising coagulated protein to centrifugal forces, such as50-4000 g.

[0039] Sedimentation may be achieved by allowing the coagulatedprotein to settle, and removing the water by decantation, such asin a settler or vessel.

[0040] After the coagulated protein has been collected, the proteinmust be washed. Washing of the coagulated protein should beachieved with washing water having a conductivity of below 1 mS/cm,preferably below 0.75 mS/cm, more preferably below 0.5 mS/cm, toobtain used washing water and washed coagulated protein. Theconductivity of the washing water, before and after use, can bedetermined by a calibrated conductivity meter. Washing is continueduntil the used washing water has a conductivity of 2 mS/cm,preferably 1.5 mS/cm, even more preferably 1 mS/cm, as describedabove. Washing can be achieved by resuspension of the collectedcoagulate protein in washing water as defined, and flushing theresuspended product over a filter. If necessary, this process canbe repeated, or additional washing water may be flushed over thefilter, until the used washing water fulfills the requirementsdescribed elsewhere.

[0041] Alternatively, washing is continued until the sugar contentof the washing water is less than 0.54 mg/g, as defined above. Thisresults in washed protein material which is not horny, as describedabove.

[0042] The washed coagulated protein is subsequently dried. Dryingmay be achieved in any known way, such as by air drying or freezedrying. Drying results in a coagulated protein powder which has awater content of 0-10 wt. %, preferably 1-7 wt. %, and usuallybetween 5-7 wt. %.

[0043] The dried protein powder generally has a protein content ofat least 85 wt. % on dry matter, preferably at least 87 wt. %, asanalyzed by Kjeldahl.

[0044] Air drying may be achieved by passing air over the washedprotein until the washed protein is a dry powder. This generallytakes from hours to days, depending on the quantity to be dried andthe temperature of the air. Preferably, the protein powder is mixedor circulated in some way, so as to achieve optimal contact betweenthe air and the protein powder, as is known in the art of dryingpowders. Air drying may be accelerated by using air at an elevatedtemperature, such as at least 50.degree. C., preferably at least80.degree. C., more preferably at least 100.degree. C., even morepreferably at least 150.degree. C., or even at least 200.degree.C., or 250.degree. C. Such conditions may suitably be achieved in avacuum belt filter, spray dryer, flash dryer, ring dryer,turbo-rotor dryer, swirl fluidizer, ultra flash spin drier,flugschicht dryer, spouting bed dryer, fluid bed dryer or any othertype of dryer where an intensive contact between wet particles andhot air is established.

[0045] Drying may also be achieved by freeze drying, which may beachieved by subjecting the wet, washed coagulated protein tosub-zero temperatures and a vacuum, so as to remove the remnantwater by sublimation. Also in this case, the protein powder ispreferably mixed during drying so as to optimize contact betweenthe vacuum and the protein powder. The temperature during freezedrying is preferably between -40.degree. C. and -90.degree. C.,more preferably between -50 and -80.degree. C., at least untilfrozen ice has disappeared. The pressure is preferably between 1and 200 mbar, preferably between 5 and 100 mbar. After the ice hasdisappeared, the temperature may be raised in order to removeremnant water from the coagulated protein material.

[0046] After drying, a coagulated root or tuber protein material isobtained as a dry powder. This powder is free from free aminoacids, sugars, phospholipids and other compounds naturally presentin potato, has a protein content of at least 85 wt. %, and is notnative.

[0047] Optionally, the method further comprises a step ofneutralizing the coagulated protein to a pH of 6.5-7. Thisneutralization step may be at any point after coagulation of theprotein, such as during, before or after collection of the protein,or during, before or after washing of the protein. Preferably, theneutralization is performed after the washing, such as by using anadditional step of neutralizing the protein product with water at apH of 6.5-7.5. The pH of the washing water may suitably be setusing conventional salts or buffers, such as phosphate, citrate orcarbonate buffers. The pH may be determined by using a pH-metercalibrated against at a temperature of 20.degree. C.

[0048] Further preferably, the neutralization is achieved byaddition of a solid base salt, such as for instance a carbonate orbicarbonate salt, to the protein prior to drying. The proteincontent of the neutralized protein product is usually 2% lower thandefined above due to addition of non-protein material.

[0049] The coagulated root or tuber protein material is optionallysubjected to a glycoalkaloid extraction procedure where the proteincoagulate is extracted with an organic- or anorganic acid at low pH(1-3.5) for the duration of 1 to 30 minutes after which theextracted protein is collected by any of the methods describedabove. The glycoalkaloid extraction procedure can be at any timeafter protein coagulation, but preferably, the glycoalkaloidextraction procedure is performed prior to the washing step.

[0050] When applying the present method, coagulated protein productcan be obtained with a small particle size as defined above,without the need of reducing the particle size by physical means,such as by grinding, milling or homogenization.

[0051] Further optionally, the coagulated, washed and dried proteinproduct is subsequently fractionated into at least a first fractionand a second fraction, that is, subjected to at least one step toseparate coarse particles from fine particles. This maybe achievedby sieving, cycloning, wind sifting or any other known way. Thisresults in at least two coagulated protein powder fractions, suchas at least a fine fraction and a course fraction.

[0052] Sieving may be achieved by placing the dry coagulatedprotein powder on a sieve of 63 .mu.m (230 mesh), so as to isolatea first, fine, fraction comprising all particles smaller than 63.mu.m, as well as a second, coarse, fraction comprising allparticles larger than 63 .mu.m. Sieving may also be achieved in acyclone (wind sieve), or in any other way, so as to achievecoagulated protein particles of specific particle size.

[0053] The fractionated protein product may be in the form of afine fraction, characterized by a d-10 of at most 12 .mu.m,preferably at most 8 .mu.m, a d-50 of at most 27, preferably atmost 23 .mu.m, and a d-90 of at most 46 .mu.m, preferably at most38 .mu.m, even more preferably at most 35 .mu.m.

[0054] The fractionated protein product may also be in the form ofa coarse fraction, characterized by a particle size of having ad-10 of between 15-38 .mu.m, preferably 15-30 .mu.m, a d-50 of42-69 .mu.m, preferably 42-61 .mu.m, and a d-90 of 150-250 .mu.m,preferably 170-210 .mu.m. The density of the coagulated proteinproduct is only marginally affected by fractionation, and iscomparable. Particle sizes of fractionated products have beendetermined by the wet method.

[0055] Coagulated protein products as obtained by the presentinvention are suitable for use in human food applications. The fineparticle size results in a good mouthfeel, and the relatively lowcoloration results in only little coloration of the food product.Furthermore, the taste of the coagulated protein product is barelynoticeable, so that the nutritious amino acid composition canfavourably be added to any food product which may benefit fromenrichment in protein.

[0056] In one embodiment, the food is a nutritious drink.Preferably, the coagulated protein powder is suspended in thedrink. Further preferably, the coagulated protein product is a finefraction of the coagulated protein product as defined above, so asto result in a stable suspension with the help of stabilizers.

[0057] In another embodiment, the food is a powdered beverage or apowder-based soup. Also, the food may be a protein, granola orother health bar, a breakfast cereal, a snack, such as an extruded,baked, fried or popped snack), a baked good or a baking mix, suchas gluten-free bread or pizza, a pasta product, such as noodles orspaghetti, a meat product, such as deli meats, injected ham orsausages, or a vegetable-based meat analogue or texturizedvegetable protein.

[0058] For the purpose of clarity and a concise descriptionfeatures are described herein as part of the same or separateembodiments, however, it will be appreciated that the scope of theinvention may include embodiments having combinations of all orsome of the features described.

[0059] The invention will now be illustrated by the followingnon-restricting examples.

EXAMPLES

Example 1

[0060] Potato juice was heat-coagulated at a temperature of104.degree. C. to obtain 12.9 gram solid protein particles/kgsuspension. The protein particles were separated from the juice bymeans of a two-phase decanter at 4000 g. The coagulated proteinobtained had a dry solid content of. 34 wt. %. A first portion ofthe coagulated protein was washed as is common in the art ofwashing coagulated protein powder and subsequently dried, whereas asecond portion was resuspended in water and sulphuric acid wasadded until a pH of 3.3 was reached in order to removeglycoalkaloids. After stirring for 30 minutes, the proteinsuspension was dewatered and thoroughly washed by means of a vacuumbelt filter.

[0061] The washing water used to wash the second portion before usehad a conductivity of 0.4 mS/cm, and washing was continued untilthe conductivity of the used washing water was below 1 mS/cm.

[0062] The thorough washing of the second portion according to theinvention took a considerably larger volume of washing water thanthe standard washing procedure applied for the first portion.

[0063] The first portion and the second portion were dried by meansof a flash dryer with an inlet/outlet temperature of 170.degree.C./80.degree. C., respectively. The wet cakes were introduced inthe hot air stream and after drying, the water content was 4.5 wt.% (see FIGS. 1a and 1b).

[0064] The conductivity was determined by using a calibrated WTWLF340 conductivity meter equipped with a Tetracon 325 probe.Calibration of the probe is carried out by Potassium chloridereference solution (1.41 mS/cm) from Merck (art nr.1.01553.0001).

[0065] Wet particle size distribution is measured by a laserdiffraction on a Malvern Mastersizer 2000G. Dry sample is added tothe water filled sample chamber until a laser obscuration level inthe range of 10 to 20% is obtained. Measurement is carried out forthe duration of approximately 2 minutes. Particle size determinedusing the wet method were converted to dry particle size bydivision, using a conversion factor of 1.3.

[0066] Particle size distribution of dry potato protein samples ismeasured by laser diffraction using a Sympatec HELIOS equipped witha RODOS dry dispenser with a vibratory feeder. The RODOS dispersingline has an inner diameter of 4 mm. Particle sized is calculated bythe integrated software using the "fraunhofer" formula.

[0067] The sugar content was determined by enzymatic analysis aspublished by megazyme (Ireland). This method makes use of asucrose/fructose/D-glucose assay kit (art no. K-SUFRG), andcomprises an UV-method for the determination of sucrose, D-fructoseand D-glucose in foodstuffs, beverages and other materials.

[0068] The color was determined by reflection. Reflected color of asample is measured by a Hunterlab Colorflex EZ spectrophotometercalibrated with the relevant Hunterlab color standards. The samplecup is filled for at least 50% of the volume with protein powderand placed on the measuring window. Reflected color is reported asthe y-value (reflection value) determined by the apparatus.

[0069] Bulk density of dried protein coagulate is measured bypouring a quantity of powder in a closed funnel with a calibratedcylinder of 0.5 liter underneath. Remove the slide of the funneland allow the powder to flow freely into the cylinder. The excessof powder is scraped off with a ruler and the weight of the powderfilled cylinder is measured on a Mettler Toledo PG5002-S scale. Thefree settled density of the powder is reported as g/l aftersubtraction of the weight of an empty cylinder.

TABLE-US-00001 TABLE 1 washing of the protein cake with washingwater having no sugars and a conductivity of 0.4 mS/cm Used washingwater Total sugar Color Time conductivity content Wash water T = 0min 2.2 mS/cm 0.54 mg/g Slightly yellow T = 15 min 2.0 mS/cm 0.54mg/g Slightly yellow T = 17 min 1.5 mS/cm 0.30 mg/g Slightly yellowT = 20 min 1.0 mS/cm 0.14 mg/g No color

TABLE-US-00002 TABLE 2 Comparison of non-horny material accordingto the invention with conventional, horny coagulated proteinpowder. particle size (determined using wet method) sugar bulk d-10d-50 d-90 content TGA density [.mu.m] [.mu.m] [.mu.m] mg/g mg/kgcolor g/l non-horny 19 42 100 0.33 81 0.62 336 coagulated Washedprotein powder (FIG. 1a) horny 31 115 492 10 1253 0.41 550coagulated conventionally washed protein powder (FIG. 1b)

Example 2

[0070] Potato juice was heat-coagulated at a temperature of104.degree. C. to obtain 12.9 gram solid protein particles/kgsuspension. The protein particles were concentrated by means of ahydrocyclone to a solid concentration of 27.5 gram solid proteinparticles/kg.

[0071] To separate the particles from the liquid, the suspensionwas filtered using a filter element. After a filter-cake was formedon the filter element, the suspension inside the filter wasreplaced with acidified water (solution of 0.5% sulphuric acid inwater, pH=1.3, conductivity Q=22 mS/cm) to effect an acid wash for30 minutes. Subsequently, the sulphuric acid solution in the filterwas replaced by cold water (conductivity 0.4 mS/cm) and furtherwashed until the conductivity fell below 1 mS/cm in the filtrate.The color of the filtrate gradually improved as a result of thewashing (FIGS. 2 & 3).

[0072] The protein cake inside the filter was dewatered by means ofcompressed air. Finally the cake was in a flash drier at160.degree. C. incoming air to a moisture content of 4.2 wt. %. Theanalytical data of the dry product were as followed:

TABLE-US-00003 TABLE 3 TGA analyses of dried, acid washed potatoprotein and dried untreated potato protein Dried washed Typicaluntreated protein potato protein TGA <52 mg/kg 1000-1500mg/kg

[0073] In table 3 it can be seen that "total glycoalkaloid content"of the dried potato protein is below the detection limit, which issufficient for use in human food applications.

Example 3

[0074] Potato juice was heat-coagulated at a temperature of104.degree. C. to obtain 12.9 gram solid protein particles/kgsuspension. The protein particles were separated from the juice bymeans of a two-phase decanter at 4000 g. The protein cake obtainedhad a dry solid content of 36.3 wt. %. The protein cake (86 kg) wasresuspended in (420 liter) cold water to obtain a proteinsuspension of 6 wt. % solids. The coagulated protein was rinsed inthis suspension by lowering the pH to a value of 3.2 by adding 10kg sulphuric acid solution (10 wt. %), and subsequent filtering.The obtained solution had a conductivity of 2.3 mS/cm.

[0075] Sample 1. Preparation of a thoroughly washed sample (withoutneutralization).

[0076] To separate the protein particles from the rinsing liquid acandle filter was used. After 150 liter of filtrate was obtainedwith a pH of 3.5 and a conductivity of 2.35 mS/cm, the liquid(protein suspension) between the filter elements was replaced bycold water (conductivity 0.4 mS/cm). From that moment the thoroughwashing of the filter cake started. During the washing theconductivity of the filtrate was measured and the washing wascontinued until a value below 1 mS/cm. From that moment the washwater was replaced by air and the filter cake was dewatered to awater content of 72 wt. %. The sample was dried in a ring dryer toobtain a fine off-white powder.

[0077] Sample 2. Preparation of a thoroughly washed sample (withneutralization).

[0078] To separate the protein particles from the rinsing liquid acandle filter was used. After 150 liter of filtrate was obtained,the liquid (protein suspension) between the filter elements wasreplaced by cold water. From that moment the thorough washing ofthe filter cake started. During the washing the conductivity of thefiltrate was measured and decreased to a value below 1 mS/cm. Fromthat moment the wash water was replaced by air and the filter cakewas dewatered to a water content of 72 wt. %. The filter cake wasneutralized in a batch mixer to a pH-value between 6.5 and 7 byadding 60 gram of dry potassium carbonate to 6 kg of filter cake.The sample was dried in a ring dryer to obtain a fine off-whitepowder.

[0079] Sample 3. Preparation of a thoroughly washed sample (withneutralization) of very fine particles.

[0080] To obtain a very fine powder, part of the dry product sample2, was wind-sifted using an Alpine Microplex MP 132. In this way afine and a course fraction was obtained. The fine fraction wasevaluated for its properties.

[0081] Sample 4. Preparation of a conventionally rinsed sample(with neutralization).

[0082] To separate the protein particles from the rinsing liquid acandle filter was used. After 150 liter of filtrate was obtained,the liquid (protein suspension) between the filter elements wasreplaced by air and the filter cake was dewatered to a watercontent of 70 wt. %. The filter cake was neutralized in a batchmixer to a pH-value between 6.5 and 7 by adding 60 gram drypotassium carbonate to 6 kg of filter cake. The sample was dried ina ring dryer to obtain a yellowish powder.

[0083] Sample 5. Preparation of an intermediate sample (withneutralization).

[0084] The neutralized filter cake from sample 2 and 4 were mixedin a 1:1 ratio in a batch mixer. The mixture was dried in a ringdryer to obtain an intermediate product.

TABLE-US-00004 TABLE 4 overview of prepared samples thorough washSample conventional according Wind- 1 rinse to inventionNeutralizing Drying sifting 1 Yes Yes No (pH = 3-3.5) Yes No 2 YesYes Yes (pH = 6.5-7) Yes No 3 Yes Yes Yes (pH = 6.5-7) Yes Yes 4Yes No Yes (pH = 6.5-7) Yes No 5 Yes comparative Yes (pH = 6.5-7)Yes No

[0085] To determine the effect of washing on the particle size ofthe dry product, samples 2, 4 and 5 were compared. Also see FIG.4.

TABLE-US-00005 TABLE 5 particle size of dry powder obtained bywashing according to the invention, conventional washing and nowashing. d-10 d-50 d-90 >425 .mu.m Potato protein Sample 2 27.mu.m 65 .mu.m 210 .mu.m 2.8% (thoroughly washed) Potato proteinSample 5 30 .mu.m 83 .mu.m 448 .mu.m 14.2% (comparative) Potatoprotein Sample 4 37 .mu.m 124 .mu.m 645 .mu.m 26.3% (conventionallywashed)

[0086] Sample 3 was subjected to fractionation to obtain a coursefraction and a fine fraction. The results are given in table 6.

TABLE-US-00006 TABLE 6 particle size distribution of the coarse andfine fractions of a coagulated protein product. Feed Fine fractionCoarse fraction d-10 27 gm 10 gm 30 gm d-50 65 gm 21 gm 61 gm d-90210 gm 35 gm 188 gm Quantity 8 kg (100%) 1.5 kg (20%) 6.5 kg(80%)

[0087] The five different dry samples were evaluated for use asfood-ingredient by a well trained sensoric panel (8 persons).

TABLE-US-00007 TABLE 7 Analyses of the dry potato powder. Sensoryevaluations were performed as a 5% suspension in water. sample 1 23 4 5 Dry matter 945 969 942 945 947 content [g/kg] Protein content888 868 855 861 866 [g/kg] Ash [mg/kg] 5.3 42.7 38.4 38.1 43.1 pH3.5 6.3 6.4 6.1 6.6 Color 0.62 0.58 0.62 0.48 0.55 d-10 24 27 13 3730 d-50 59 65 27 124 83 d-90 144 210 45 645 448 taste acidicNeutral/slightly bitter mouthfeel lightly lightly not sandy verysandy sandy sandy sandy astringency medium low odor low Conclusionacceptable in food application not acceptable in foodapplications

[0088] From the table can be concluded that the samples which arethoroughly washed have the desired (organoleptic) properties forfood application. The neutralized product has an improved taste forapplications in a pH-neutral environment. In applications weremouthfeel is very important the fine fraction has the bestperformance in regard to mouthfeel.

[0089] Protein content on dry matter is determined by Kjeldahlmethod using a FOSS Kjeltec 8400 automated protein analysis system.A conversion factor of N.times.6.25 is used to convert nitrogenlevel to protein.

[0090] Ash content was determined by weighing a quantity of 5 gramprotein accurately (error 0.1 mg) and heating for at least 3 hoursin a 550.degree. C. oven. After 3 hours the sample is cooled downto room temperature in an exsiccator and weighed again (0.1 mgaccuracy).

[0091] The pH of the suspension is measured in a 1 gram/100 mlsuspension in demineralized water by a calibrated pH meter.

Example 4

[0092] To determine the sedimentation behavior of the variousprotein samples prepared in example 3 a sedimentation test wasperformed. For this, 5 gram of protein powder was added to 95 gramof room temperature tap-water. The mixture was stirred to obtain ahomogenous protein suspension. The suspension was transferred to a100 ml measuring cylinder and the time was recorded. Sedimentationrate was measured by the sediment volume at the bottom of thecylinder at regular time intervals. The results can be seen in FIG.5. It was found that coagulated protein which had been washed untilthe washing water had a conductivity of less than 1 mS/cm displayedslower sedimentation than non-washed or conventionally washedsamples. It is irrelevant whether the protein has been neutralizedor not.

[0093] Reduced sedimentation was observed for the fine fraction ofthe coagulated protein product.

Example 5

[0094] To be able to correlate the particle size as determined bythe wet and dry methods, the following experiment wasperformed.

[0095] Potato protein was produced by means of the followingprocess steps: [0096] heat coagulation of potato juice by directsteam injection (pH=5.5 and 104.degree. C.). [0097] recovery ofsolid protein by means of a decanter (at 4000 g) [0098]resuspension of the protein cake in water (to a suspension of 6%ds). [0099] TGA extraction with sulphuric acid (at pH=3.3) [0100]Filtration and washing of protein cake with cold water (untilconductivity <1 mS/cm) [0101] Drying of the cake in a flashdrayer (at a T-in/T-out of 180/70.degree. C.). [0102] Differentsamples in size were produced with a windsifter (wheel: between2600-5300 rpm).

[0103] From the different samples the d-10, the d-50 and d-90[.mu.m] were analyzed by both the wet and the dry method (see FIG.6). The dry particle size was analyzed with Sympatec Helios &Rodos as described above, and the wet particle size was analyzedwith Malvern Mastersizer 2000G as described above.

[0104] From the graph it can be seen that the d-10, d-50 and d-90(.mu.m) value of a sample resuspended in water is a factor1.3.times.higher than the d-10, d-50 and d-90 (.mu.m value) of thedry particles. This increase in diameter of the particles(expansion/swelling) can be explained by the absorption of water.This value has been used as a conversion factor to report allparticle size values determined using the wet method as particlesize determined using the dry method. It has been indicated when aparticle size has been determined using the wet method, even thoughthe calculated result for the dry method is reported.

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