METHOD OF PREPARING LIQUID OAT BASE
FIELD
[0001] The present invention relates to a method of preparing liquid oat base, in particular a high-protein, non-dairy liquid oat base, which can be used in the manufacture of various oat-based products for human consumption. In particular, the method according to the invention comprises ultrasonication and enzyme treatment of oat raw materials. The invention also relates to non-dairy liquid oat bases, to products prepared therefrom and to the use of ultrasonication for improving solubility of oat proteins and colloidal stability of liquid oat bases. BACKGROUND
[0002] Oat or oats (Avena sativa ) is a species of cereal grain associated with various health benefits. The beneficial effects of oat are linked to reduction of blood cholesterol levels, reduction of blood glucose rise, and gut health. Compared to other cereals, oat contains more fat, protein, and soluble fibre, and is especially rich in b-glucan. The major storage proteins in oats are globulins, while prolamins constitute minor proteins of oat. Globulins are characterised by solubility in dilute salt solutions and limited solubility in water.
[0003] Oats have been traditionally consumed as breakfast cereals and in bakery products. During the last years, various new oat based products have been developed. Examples of oat based products include non-dairy products such as oat milk, oat based beverages, creams, desserts and fermented products, for example yoghurt-like products.
[0004] Methods for preparing various oat based drinks have been disclosed in several prior art publications, including i.a. EP 1123012 A2, EP 2205101 Al, and EP 2996492 Al. The methods typically comprise aqueous extraction of oats, an enzymatic treatment to degrade starch, in particular enzymatic treatment with a-amylases and/or b- amylases, and separation of insoluble components such as fibres. Conventional oat milk produced by an industrial process contains approx. 90% water and approx. 10% oats. Recently, various oat based health drinks or recovery drinks have been developed, such as an oat drink comprising oligosaccharides (US 8337880) or an oat based drink comprising carbohydrates having a high glycemic index (WO 2017018917 Al).
[0005] However, the poor solubility of oat proteins (globulins) in aqueous solutions has lowered the potential of oats in preparing high protein oat based products. Previous attempts to improve solubility of oat proteins include enzymatic hydrolysis (Guan et al, 2007), fermentation (Loponen et al, 2007), succinylation, deamidation (Mirmoghtadaie et al, 2009), non-polar lipid removal, pH adjustment, heat treatment (Konak et al, 2014) and cross-linking (Nivala et al, 2017).
[0006] Ultrasound is an acoustic wave with a frequency at the same level or higher than the threshold of human audio detection, 20 kHz. Ultrasound can be divided into high frequency ultrasound with low power (100-1000 kHz and < 1 W/cm2) and low frequency with high power (20-100 kHz and 10-1000 W/cm2). High frequency ultrasound is used for analyzing food, while low frequency ultrasound is increasingly studied for alteration of food (O’Sullivan et al, 2016).
[0007] Ultrasound, or sonication or ultrasonication, has been commercially used for vegetable puree mayonnaise and fruit juice processing for homogenization and modification of viscosity (Patist & Bates, 2008). It has recently been observed that also the structure of proteins can be modified by the ultrasonic cavities generated during sonication (O’Sullivan et al, 2017). Ultrasonic cavities are formed when ultrasound generated gas bubbles are rapidly formed and collapsed due to localized pressure gradients. The collapse of bubbles is associated with hydrodynamic shear forces and significant temperature raise, which are causing the ultrasound effect.
[0008] Ultrasound can have beneficial effects on the physicochemical properties of food proteins. Ultrasonication may offer improvement in solubility of protein, by reducing the size of protein aggregates and allowing more protein-water interactions. Other reported results from ultrasound treatment are increased intra-mo lecular mobility and surface activity, as well as changes in free sulfhydryl groups secondary structure, surface hydrophobicity and particle size.
[0009] Hu et al, 2013 observed increase of soy globulin solubility after ultrasound treatment, while it had no significant effect on the protein primary structure. On the other hand, O’Sullivan et al (2016) reported particle size reduction in soy protein isolate after ultrasound treatment at 20 kHz frequency and 34W power.
[0010] In the method of WO 2004/085484 Al, high viscosity beta-glucan products are prepared through methods involving sonification or sonification and enzymes. The method comprises mixing flour, particularly a pearled grain flour of barley or oats, with an alcohol, separating a fiber residue, mixing the fiber residue with an alcohol and subjecting the mixture to a sonification, or to a protease or amylase treatment step, or to both, and separating the final fiber residue product having a high beta-glucan content.
[0011] Ultrasound treatment was found to improve pea protein gelation compared to heat induced gelation in a study by Ruikka, 2018. CN 105166645 A discloses a method for preparing oat bran powder, wherein the method comprises enzymatic hydrolysis and subjecting the enzymatic hydrolysate to ultrasonic extraction. In CN 105725056A, quinoa powder is prepared by mixing quinoa and oats, carrying out enzymolysis and ultrasonic wave auxiliary extraction and microwave extraction before concentrating and drying to powder. CN 101849606 A discloses a method for preparing oat antihypertensive peptides by simultaneous enzymolysis and ultrasound treatment.
[0012] However, the effect of ultrasound on oat proteins has not been studied or suggested, although there are studies with other plant proteins, for example soy and pea proteins. In particular, ultrasonication of oat raw material subjected to at least one enzymatic treatment to increase the solubility of oat and to obtain a high-protein liquid oat base has not been disclosed, nor a method of ultrasonicating the oat raw material or a liquid oat base after enzymolysis to improve colloidal stability.
SUMMARY OF THE INVENTION
[0013] The invention is defined by the features of the independent claims. Some specific embodiments are defined in the dependent claims.
[0014] The present invention is based on the concept of using ultrasonication (ultrasound treatment) for modification of oat proteins to render said proteins more soluble without affecting the primary structure of the proteins. The finding that ultrasound treatment significantly improves solubility of oat proteins without degrading the protein primary structure finds use in various embodiments, particularly in a method of preparing high-protein oat-based products.
[0015] According to a first aspect of the present invention, there is thus provided a method of preparing a liquid oat base suitable for human consumption, the method
comprising the steps of ultrasonicating an aqueous suspension comprising oat raw material subjected to at least one enzymatic treatment and recovering the obtained liquid oat base.
[0016] According to a second aspect of the present invention, there is provided a high-protein liquid oat base, obtainable by the method according to the present invention.
[0017] According to a third aspect of the present invention, there is provided a high- protein liquid oat base having a protein content of at least 1.5%.
[0018] According to a fourth aspect of the present invention, there are provided food products comprising the liquid oat base of the invention.
[0019] According to a fifth aspect of the present invention, there is provided the use of the liquid oat base of the invention for preparing oat based products for human consumption.
[0020] According to a sixth aspect of the present invention, there is provided the use of ultrasonication for improving solubility of oat proteins, particularly for improving solubility of oat proteins in the manufacture of liquid oat bases, particularly high-protein non-dairy liquid oat bases.
[0021] According to the seventh aspect of the present invention, there is provided the use of ultrasonication for improving colloidal stability of oat suspensions or liquid oat bases, particularly for improving colloidal stability of liquid oat bases and food products comprising said liquid oat bases.
[0022] Considerable advantages are obtained by the invention. The present invention enables to achieve improvement in the solubility of oat proteins without degradation of the protein structure. The process according to the present invention produces an increased amount of soluble oat protein compared to the prior art processes which are based on enzymatic treatment only. The process according to the present invention thus enables to produce high-protein liquid oat bases from oat without having to use complementary protein sources.
[0023] Further, the present invention enables to achieve improvement in the colloidal stability of the liquid oat bases, resulting in slower sedimentation of the colloidal particles during storage. Sedimentation is a common problem related to liquid oat bases and oat based liquid food products. Improved stability of liquid oat bases provides better
processability and higher quality of the oat based liquid food products comprising liquid oat bases of the invention.
[0024] Further features and advantages of the present technology will appear from the following description of some embodiments. BRIEF DESCRIPTION OF THE FIGURES
[0025] FIGURE 1 illustrates the solubility of oat flour proteins after ultrasonication at different pHs, when whole grain oat flake flour was used as a starting material. Samples in Figure 1 are the following: 1) hydrolyzed pH 3.07; 2) hydrolyzed pH 6.32; 3) hydrolyzed pH 8.47. [0026] FIGURE 2 illustrates the solubility of oat proteins after ultrasonication at different pHs, when oat protein concentrate (non-hydrolyzed or after hydrolysis using amylase enzymes) was used as a starting material. Samples in Figure 2 are the following: 1) non-hydrolyzed pH 2.9; 2) non-hydrolyzed pH 6.38; 3) non-hydrolyzed pH 8.49; 4) hydrolyzed pH 3.1; 5) hydrolyzed pH 6.38; 6) hydrolyzed pH 8.45. [0027] FIGURE 3 shows SDS-PAGE gel run under reduced conditions for ultrasonicated oat samples and non-ultrasonicated controls, showing the molecular weight distribution of proteins. Samples in Figure 3 are the following: OP) Oat protein concentrate, non-hydrolyzed and centrifuged; OPU) Ultrasonicated OP; OPNF) Oat protein concentrate, non-centrifuged; OPNFU) Ultrasonicated OPNF; OPH) Oat protein concentrate, hydrolyzed and centrifuged; OPHU) Ultrasonicated OPH; OFH) Oat flour, hydrolyzed and centrifuged; OFHU) Ultrasonicated OFH.
[0028] FIGURE 4 shows the solubility of oat proteins after ultrasonication at different temperatures, when oat flour or oat protein concentrate was used as a starting material. The samples were hydrolysed using amylase enzymes either before or after ultrasonication. Non-ultrasonicated hydrolysed samples were used as controls.
EMBODIMENTS
[0029] DEFINITIONS
[0030] In the present context, the term“oat raw material” refers to oats in any of its forms which comprises oat protein, including but not limited to oat whole grains, dehulled
oat grains (oat groat), dehulled and heat-treated oat grains, rolled oats (flakes), steel-cut oats, oat flour or oat meal, both whole grain oat flour and non-whole grain oat flour, oat protein concentrate, oat bran, oat fiber, and a by-product or residual fraction from the production of oat milk (destarched oats). [0031] In the present context, the term“oat base”, particularly a“liquid oat base”, refers to a product, which is in principle edible as such but which is usually formulated or processed further into products for human consumption, for example by adding fats, salt, minerals, suitable flavours, by fermenting etc.
[0032] Within the present context, the term“high-protein” refers to a higher protein content in the liquid oat base than can be achieved by the state-of-the-art methods from the corresponding oat raw material, i.e. by methods which do not comprise ultrasonication. For example, the method according to the present invention provides liquid oat bases wherein the protein content is at least 1.6 times higher than the protein content of currently available liquid oat bases prepared without ultrasonication from whole grain oat flour. [0033] Particularly, the term“high-protein” in the context of the oat base refers to an oat base which comprises at least 1.5%, preferably at least 1.7%, more preferably at least 2%, even more preferably 2.5%, of soluble protein in the oat base solution or dispersion.
[0034] ‘Non-dairy” in this context means that the product referred to as non-dairy resembles a dairy product based on its taste, appearance, mouthfeel, functionality and/or end uses, but is free from milk-based ingredients.
[0035] The present invention is based on the finding that ultrasound treatment significantly improves solubility of oat proteins without degrading the primary protein structure. Ultrasound treatment of oat can thus be utilized for increasing the protein content of oat based products, particularly for increasing the protein content of a liquid oat base which can be formulated into various products for human consumption.
[0036] The method according to the invention for preparing a high-protein non-dairy liquid oat base for use in the manufacture of food for human consumption thus comprises the step of ultrasonicating an oat-water suspension obtained by at least one enzymatic treatment (hydrolysis) of aqueous suspension comprising oat raw material.
[0037] In an embodiment, the method of preparing a high-protein liquid oat base suitable for human consumption thus comprises the step of ultrasonicating an aqueous suspension comprising oat raw material subjected to at least one enzymatic treatment. The embodiment, wherein hydrolysed oat suspension is subjected to ultrasonication, preferably by using low frequency ultrasound with high power (such as 10-100 kHz and 10-1000 W/cm2) , provides a higher protein content than can be achieved without ultrasonication. Moreover, the primary structure of the oat proteins remains unaffected. In a preferred embodiment, after ultrasonication any insoluble fibre and other insoluble components are removed from the hydrolysed oat suspension to obtain a high-protein liquid oat base.
[0038] When the method according to the invention comprises the step of removing any insoluble fibre and other insoluble components, e.g. by centrifugation or filtration, typically by a decanter centrifuge (decanting), said step is arranged before or after the ultrasonication step, preferably after the ultrasonication step.“Decanting” in the present context refers to separation of the insoluble components (insoluble fibre and other insoluble components) from soluble components by using a decanter centrifuge.
[0039] In a further embodiment, the aqueous suspension comprising oat raw material subjected to at least one enzymatic treatment is a liquid oat base from which any insoluble fibre and other insoluble components have been removed, e.g. by decanting, before the ultrasonication step. Typically this embodiment provides liquid oat bases with improved colloidal stability. Also a further embodiment which does not comprise the step of separating insoluble components provides oat suspensions with improved colloidal stability.
[0040] In an embodiment, the method according to the invention also comprises heat treatment of the enzymatically treated aqueous suspension (hydrolysed oat suspension) to inactivate the enzymes.
[0041] In an embodiment, the method of the invention for preparing a liquid oat base suitable for human consumption comprises the following steps: a) providing oat raw material and optionally reducing the particle size of the oat raw material by grinding or milling; b) mixing the oat raw material with an aqueous media, in particular water, to form an aqueous suspension comprising oat raw material;
c) subjecting the aqueous suspension comprising oat raw material to enzymatic treatment by contacting the aqueous suspension with enzymes, preferably amylases, in particular a- amylases, to obtain a hydrolysed oat suspension; d) optionally subjecting the hydrolysed oat suspension to a further enzymatic treatment, by contacting the hydrolysed oat suspension with enzymes or a combination of enzymes, preferably amylases, in particular b-amylases or glucoamylases, or proteases, in particular endoproteases, or protein modifying enzymes, in particular deamidases or transglutaminases, or cell wall degrading enzymes, in particular b-glucanases, cellulases or xylanases; e) optionally heating the hydrolysed oat suspension to inactivate the enzymes; f) optionally decanting the hydrolysed oat suspension to separate any insoluble components and to obtain a liquid oat base; g) recovering the liquid oat base; and h) optionally formulating or further processing the liquid oat base to products for human consumption; wherein the method comprises the step of ultrasonicating the hydrolysed oat suspension to obtain a high-protein liquid oat base, or the step of ultrasonicating the liquid oat base to obtain a liquid oat base with improved colloidal stability.
[0042] In particular, the method of the invention comprises the step of ultrasonicating the hydrolysed oat suspension obtained by at least one enzymatic treatment of the aqueous suspension comprising the oat raw material.
[0043] In the embodiment disclosed above, ultrasonication is being arranged after step c).
[0044] In one embodiment, ultrasonication is being arranged between steps c) and d), or after step d), if step d) is present.
[0045] In one embodiment, ultrasonication is being arranged after step e), if step e) is present.
[0046] In one embodiment, ultrasonication is being arranged after step f), if step f) is present.
[0047] In embodiments, ultrasonication of the liquid oat base may thus be arranged after step c), between steps c) and d), after step d), after step e), after step f), or any combinations thereof in case two or more ultrasonication steps are carried out.
[0048] In particular, ultrasonication of the hydrolysed oat suspension is being arranged after step c) and between steps e) and f), if steps e) and f) are present.
[0049] In one embodiment, ultrasonication is being arranged after step c) and before step e), if step e) is present
[0050] In an embodiment where decanting step f) is present, ultrasonication step is being arranged after step c) and before or after the decanting step, preferably before the decanting step.
[0051] In an embodiment, the ultrasonication step can be carried out twice or more times, for example after step c) and before or after step g).
[0052] In the step of ultrasonicating the hydrolysed oat suspension or the liquid oat base, in principle any technique which provides cavitation forces to the material to be treated is applicable. In an embodiment, low frequency ultrasound with high power is used. In a preferred embodiment, ultrasound treatment with a frequency of about 20 kHz to 100 kHz, preferably about 20 kHz to 50 kHz, is used, particularly ultrasound treatment with a frequency of about 20 kHz. Ultrasonication time varies depending on the frequency and amplitude used for the ultrasound treatment. In an embodiment, the ultrasonication time in the method of the present invention varies from few seconds to couple of minutes, for example from 2 seconds to 10 minutes, particularly from 30 seconds to 5 minutes, or from 60 seconds to 2 minutes, when ultrasound treatment with a frequency of 20 kHz is used.
[0053] The protein content of the oat raw material varies depending on the form of the oat raw material. As an example, whole grain oat flour typically has a protein content of 10-17%, particularly 14-15%, while oat protein concentrate usually has a protein content of above 16%, typically above 18%.
[0054] The oat raw material is mixed with an aqueous media, in particular with water, to form an aqueous suspension comprising the oat raw material. In an embodiment
the oat raw material and the aqueous media are mixed in a ratio between 1 :3 and 1 :12, particularly in a ratio between 1 :5 and 1 :9. In an embodiment, the aqueous media and the oat raw material are mixed to obtain a 15 to 20% oat suspension. The temperature of the aqueous media is preferably higher than room temperature, such as above 40°C, preferably above 60°C, such as about 70°C. Mixing is continued until the oat raw material has been thoroughly mixed with aqueous media, for example for 5 to 10 minutes, to allow gelatinization of the oat starch.
[0055] The aqueous suspension comprising the oat raw material is subjected to enzymatic treatment, preferably to enzymatic treatment with amylases, in particular with a- amylases, to provide at least partial hydrolysis of starch in the oat raw material.
[0056] Enzymatic hydrolysis of starch of various oat raw materials is as such known to persons skilled in the art. In short, enzymatic hydrolysis can be carried out for example by mixing the enzymes, particularly a- and/or b-amylases, with an aqueous suspension of the raw material to be treated, at a pH, temperature and dose recommended for the particular enzymes. To achieve efficient hydrolysis of starch, it is preferred to gelatinize the starch by heating the aqueous suspension to above the gelatinization temperature, which is approximately 58-65°C for oat starch. Efficient hydrolysis also requires regular/constant mixing. The hydrolysis time can vary from some minutes to several hours depending on the enzyme, dose, environmental factors and desired level of hydrolysis. After enzymatic hydrolysis the enzymes are typically inactivated by heating the suspension above the inactivation temperature of the enzymes (typically 80-95 °C), in order to achieve a stable product.
[0057] After enzymatic treatment, the hydrolysed oat suspension is preferably subjected to heat treatment to inactivate the enzymes. Typically the suspension is heated to above 90°C, for example to 95 °C, for an appropriate period of time, for example 5 to 15 minutes.
[0058] When the method comprises a step for separation of any insoluble fibre and other insoluble components, in a preferred embodiment the separation is performed by using a decanter centrifuge (decanting).
[0059] In order to prevent rancidity, in embodiments of the invention it is possible to use protective agents or protective measures. Protective agents include but are not limited
to antioxidants, while protective measures include for example treatment under vacuum or nitrogen.
[0060] Surprisingly, ultrasonication of the aqueous oat suspension comprising whole grain oat flour increases the amount of oat protein in the liquid oat base to at least 1.5%, preferably to at least 1.7%, based on the total oat protein recovered in the liquid oat base after decanting, while without sonication, a protein content of only 0.8-1% is achievable with the corresponding method and raw material.
[0061] Depending on the oat raw material and oat to water ratio, a protein content of for example from at least about 1.5% to about 2.6% in the liquid oat base can thus be achieved by the method of the invention. By selecting an oat raw material with a high protein content and by adjusting the oat to water ratio, higher protein content in the liquid oat base can be achieved. When the oat raw material is whole grain oat flour, the method of the invention provides oat bases with approximately 1.5- 1.7% protein, while without sonication approximately 0.5-1% protein content is achievable. Correspondingly, using oat protein concentrate as starting material in the method of the present invention provides oat base liquids with 2.3-2.6% protein while the corresponding method without sonication leads to a protein content of approximately 1-2%
[0062] The recovered high-protein non-dairy liquid oat base can be formulated into various products with increased protein content, preferably without using complementary protein sources. Examples of such products include but are not limited to drinkable or spoonable products or semi-solid yogurt or cheese-like products, cooking products, egg replacers, fermented oat products, meat analogues or liquid or powdered oat protein concentrates or isolates.
[0063] It is to be understood that the embodiments of the invention disclosed are not limited to the particular structures, process steps, or materials disclosed herein, but are extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting.
[0064] Reference throughout this specification to one embodiment or an embodiment means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present
invention. Thus, appearances of the phrases“in one embodiment” or“in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Where reference is made to a numerical value using a term such as, for example, about or substantially, the exact numerical value is also disclosed.
[0065] As used herein, a plurality of items, structural elements, compositional elements, and/or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. In addition, various embodiments and example of the present invention may be referred to herein along with alternatives for the various components thereof. It is understood that such embodiments, examples, and alternatives are not to be construed as de facto equivalents of one another, but are to be considered as separate and autonomous representations of the present invention.
[0066] Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.
EXPERIMENTAL
Ultrasound treatment with pH adjustment
[0067] Ultrasound treatments were done in a pilot ultrasonication unit. For ultrasound treatments, different oat-water suspensions were prepared from whole grain oat flour or oat protein concentrate. From both raw materials, a slurry after starch hydrolysis using amylase enzymes was prepared. From oat flour, only hydrolyzed samples were prepared, whereas from oat protein concentrate, both hydrolyzed and non- hydrolyzed slurries were prepared for ultrasound treatment. Ultrasound treatment was tested at three
different pH’s: native (around 6.3) or adjusted to approximately pH 3 or 8.5. Different samples are presented in Table 1.
Table 1. Samples for ultrasound treatment with pH adjustment
Raw Material pre- treatment pH Protein content (%)
Oat flour Starch hydrolysis 3 2.24
Oat flour Starch hydrolysis 6.5 2.24
Oat flour Starch hydrolysis 8.5 2.24
Oat protein Starch hydrolysis 3 3
concentrate
Oat protein Starch hydrolysis 6.5 3
concentrate
Oat protein Starch hydrolysis 8.5 3
concentrate
Oat protein - 3 3
concentrate
Oat protein - 6.5 3
concentrate
Oat protein - 8.5 3
concentrate
[0068] Before ultrasonic treatment, hydrolyzed and non- hydrolyzed oat suspensions were diluted with water to 2-3% protein content and samples were cooled in ice bath to 5- l0°C. Chilled samples were ultrasonicated for fixed time with constant frequency with the sonication probe. Samples were centrifuged at room temperature to remove insoluble components and obtain a supernatant. [0069] Protein solubility was determined from the volume and protein concentration of the supernatants after centrifugation. The protein concentration was measured by using DC protein assay kit (BIO-RAD).
[0070] Colloidal stability was evaluated from supernatants as well as from non- centrifuged suspensions. Colloidal stability was evaluated by visually monitoring sedimentation in the samples while standing at room temperature. Density and height of the sediment was visually evaluated at Omin lOmin, 20min, 40min and 60min.
[0071] Ultrasonication substantially improved the solubility of oat protein.
Ultrasonication of hydrolyzed oat flour doubled the protein solubility (23-34% vs. 39-64%) compared to the non-sonicated control samples. Protein solubility of samples prepared from oat flour is presented in Figure 1. Samples in Figure 1 are the following: 1) hydrolyzed pH 3.07; 2) hydrolyzed pH 6.32; 3) hydrolyzed pH 8.47.
[0072] In non-hydro lyzed samples from oat protein concentrate, the solubility of protein increased slightly after ultrasonication. The solubility of these samples (30-45%) before ultrasonication was moderately higher when compared to hydrolyzed samples. In the hydrolysed samples, the solubility improved significantly after ultrasonication and resulted in higher protein solubility than in ultrasonicated non-hydrolyzed samples. The solubility of oat proteins from oat protein concentrate after ultrasonication is presented in Figure 2. Samples in Figure 2 are the following: 1) non-hydrolyzed pH 2.9; 2) non- hydrolyzed pH 6.38; 3) non-hydrolyzed pH 8.49; 4) hydrolyzed pH 3.1; 5) hydrolyzed pH 6.38; 6) hydrolyzed pH 8.45. [0073] Ultrasonication at native or acidic pH improved the colloidal stability of non- centrifuged suspensions from oat flour. By contrast, ultrasonication at alkaline pH decreased the stability. However, it should be noted that the stability at alkaline pH was already high without ultrasonication. Stability of non-centrifuged suspensions from oat protein concentrate was unaffected or decreased by ultrasonication regardless of the pH. Temperature of all oat suspensions increased during ultrasonication, whereas the pH either decreased slightly or remained unaffected. The results are shown in Table 2.
Table 2. pH and stability of ultrasonicated samples. + = improvement, 0 = no effect, -
= decrease. 1) oat flour 2) oat protein concentrate
Raw Pre- Ultrasonic. T (°C) pH prior pH after Change in material treatment T (°C) after ultrasonic. ultrasonic, stability ultrasonic.
oat flour Starch 8.6 25.5 3.07 3.03 +
hydrolysis
oat flour Starch 8.6 25.5 6.32 6.12 ++
hydrolysis
oat flour Starch 8.6 26.6 8.47 8.3
hydrolysis
oat protein - 7.9 27.3 2.9 2.97
concentrate
oat protein - 5.7 24.6 6.38 5.81 0 concentrate
oat protein - 8.4 24.7 8.49 8.61
concentrate
oat protein Starch 8.8 25.6 3.1 3.14 0 concentrate hydrolysis
oat protein Starch 9.8 26.3 6.38 6.46
concentrate hydrolysis
oat protein Starch 8.8 25 8.45 8.38 0 concentrate hydrolysis
[0074] The ultrasonicated samples and non-sonicated controls from oat flour and oat protein concentrate (native pH) were run in SDS-PAGE under reduced conditions. The gel is shown in Figure 3. [0075] In Figure 3, the samples are the following: OP) Oat protein concentrate, non- hydrolyzed and centrifuged; OPU) Ultrasonicated OP; OPNF) Oat protein concentrate, non-centrifuged; OPNFU) Ultrasonicated OPNF; OPH) Oat protein concentrate, hydrolyzed and centrifuged; OPHU) Ultrasonicated OPH; OFH) Oat Flour, hydrolyzed and centrifuged; OFHU) Ultrasonicated OFH.
[0076] The SDS-PAGE results confirm that the primary structure of oat proteins is not affected by the ultrasound treatment. As the oat protein structure is not degraded although solubility of oat proteins is increased, products having higher protein content can be produced without having to use complementary protein sources.
Ultrasonication with temperature adjustment [0077] Ultrasound treatment at different temperatures was tested for aqueous suspensions of oat flour or oat concentrate. The temperatures were adjusted to 5-lO°C, 20- 25°C and 50-55°C before sonication. In addition, it was studied how the sequence of treatments (starch hydrolysis and ultrasonication) influences protein solubility. Samples were pre-treated and post-processed according to table 3.
Table 3. Pre- and post- treatment of ultrasound samples
Raw Pre-treatment T(°C) Post-treatment
material
prior
treatment
Oat flour Starch 5-10 Centrifugation
hydrolysis
Oat flour Starch 20-25 Centrifugation
hydrolysis
Oat flour Starch 50-55 Centrifugation
hydrolysis
Oat flour - 5-10 Starch hydrolysis, centrifugation
Oat flour - 20-25 Starch hydrolysis, centrifugation
Oat flour - 50-55 Hydrolysis, centrifugation
Oat protein Starch 5-10 Centrifugation
concentrate hydrolysis
Oat protein Starch 20-25 Centrifugation
concentrate hydrolysis
Oat protein Starch 50-55 Centrifugation
concentrate hydrolysis
[0078] Each sample was tempered to desired temperature and then ultrasonicated for fixed time with constant frequency with the sonication probe. After ultrasonication, samples were tempered to 60°C before centrifugation.
[0079] In this second series of experiments, the temperature of the samples during sonication increased about 8-l7°C. Solubility of protein clearly increased in samples which were hydrolyzed prior to ultrasonication whereas the solubility was only marginally increased in samples that were hydrolyzed after ultrasonication. Ultrasonication temperature did not have a clear effect on solubility of protein. Figure 4 shows the solubility of oat proteins after ultrasonication at different temperatures.
[0080] Ultrasound treatment improved the colloidal stability of supernatants from oat flours. As an exception, no improvement in supernatant stability was observed when oat flour suspension was sonicated at 50-55°C. The changes in stability of supernatants from oat flourare presented in table 4.
Table 4. The change in stability of supernatants from oat flours after ultrasound
treatments. + = improvement, 0 = no effect, - = decrease
Pre- T(°C) T(°C) Post-treatment Change
treatment . in
prior after stability
ultrasonic, ultrasonic.
Starch 9 24.4 CentrifUgation +
hydrolysis
Starch 24.4 38 CentrifUgation +
hydrolysis
Starch 51.2 59.4 CentrifUgation 0
hydrolysis
9.2 27.4 Starch hydrolysis, +
CentrifUgation
24.5 42.1 Starch hydrolysis, +
CentrifUgation
54 65 Starch hydrolysis, 0
CentrifUgation
[0081] While the forgoing examples are illustrative of the principles of the present invention in one or more particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and details of implementation can be made without the exercise of inventive faculty, and without departing from the principles and concepts of the invention. Accordingly, it is not intended that the invention be limited, except as by the claims set forth below. [0082] The verbs“to comprise” and“to include” are used in this document as open limitations that neither exclude nor require the existence of also un-recited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of "a" or "an", that is, a singular form, throughout this document does not exclude a plurality. INDUSTRIAL APPLICABILITY
[0083] At least some embodiments of the present invention find industrial application in food industry, particularly in the manufacture of food for human
consumption. The present invention enables to prepare high-protein non-dairy liquid oat
bases, which can be formulated to various food products, such as oat based beverages, desserts, snacks, cooking products, egg replacers, fermented oat products, cheese analogues, meat analogues, protein concentrates or protein isolates.
CITATION LIST
Patent Literature
CN 105166645 A
CN 105725056A
CN 105725056A
EP 1123012 A2
EP 2205101 Al
EP 2996492 Al
US 8337880
WO 2004/085484 Al
WO 2017018917 Al
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