[0002} The method comprises treatment of starch product with a combination of individual fatty acids and free amino acids,

[0003] The resulting starch product exhibits superior characteristics comprising reduced breakdown, low retrogradation, and good stability under freeze-tha cycles.

BACKGROUND OF THE INVENTION

[0004 ] The history of humans eating starchy food can be tracked back to the beginning of civilization. Starch from different botanical sources, including seeds, tuber and roots was heated with or without water for basic food needs. Although wheat, corn and rice are three main sources of starch with almost equal amounts of production, different cereals and starches are favored in different regions of the world. Corn is indigenous to the Americas. Asia contributed the biggest percentage of rice and wheat production to the worid in the year 201 i .

[0005] Starch is a naturally occurring polymer comprised of glucose units, amylose and araylopectin, whereas amylose units are essentially linear chains and amylopectin are typically highly branched structures,

[0006] Native starch exists in the form of starch granules, which arc packed with amorphous amylose and amylopectin in semi-crystalline rings. Most native starch has between about 10 - 40% amylose, depending on a number of factors including botanical, source, growth condition, and harvesting time. For example, amylose content ranges from 20% to 36% for corn starch; from 1 8% to 23% for potato starch; from 21 % to 35% for sorghum starch; from 17% to 29% for wheat starch; from 1 1 % to 26% for rice starch; and from 34% to 37% for pea starch.

[0007] Starches from different plant sources exhibit different size, amylose/amylopectin ratio, granule organization and granule surface compounds, which also result in different thermal, pasting and other physicochemicai properties. [0008] For use of starch within the food industry, native starches exhibits certain undesirable texture problems during cooking, it is desirable that starch remain stable when undergoing typical processes such as heating, agitation, or acid treatment. For example, while heating cause s the viscosity of starch to increase, continuous heating with stirring causes the viscosity to decrease. While not being bound by this explanation, it appears that the viscosity d ec rease i s due to the rupture of starch granule, a process which is called breakdown. When starch undergoes breakdown, the starch becomes cohesive and usually lower in viscosity than desired. Long time storage of starch under low temperature c au se starch to reerystallize and loose its softness, a process which is called retrogradation.

[0009] At room temperature, native starch is insoluble in cold water. Upon heating, as water begins to penetrate the starch granules the starch begins to swell, referred to as gelatmization. Continuous heating destroys the crystalline regions of starch granule and causes significant swelling which is a stage called pasting where the starch reaches peak viscosity. At this point, molecular order in starch granules changes accompanied by irreversible starch swelling, leaching of amylose, and granule collapse. Granule collapse results in decreased viscosity of the starch.

[0010] After gelatmization occurs, additional heating may cause significant disruption of starch granules causing the starch viscosity to decrease until it reaches minimum viscosity. The difference between peak viscosity and minimum viscosity is called breakdown. This characteristic of starch defines stability of starch during cooking, or vulnerability of starch to being disrupted by other factors, such as shearing or acidic conditions, which also can accelerate starch granule collapse and breakdown.

[0011] Cooling starch product after gelatmization and pasting occurs causes an increase its viscosity, due to what is believed to be the association of starch gel. This process is called starch retrogradation. For example, starch retrogradation appears to be the main reason for bread staling or undesirable firming of other starchy food. Native starch with a high retrogradation rate would not be suitable in frozen food. High retrogradation may be a desirable attribute for products that require crispy structure and low stickiness, such as breakfast cereal,

[0Θ12] It is desirable to be able to stabilize starch product to control breakdown and retrogradation. PRIOR ART

[0013] Conventionally, to restrain swelling o r g e l at i n i z at i o n , food starches have been m od ified by crosslinking the starch with a variety of chemicals, fo r e x am p l e , phosphoryl chloride, sodium trimetaphosphate (STMP), orthophosphate, adipic acid or acetic acid.

[0014] Typically, starch is mixed with a crosslinking agent in a neutral or basic aqueous solution, dried, and then heated. Acid is used to terminate the reaction.

[0015] In U.S. Patent. No. 2,884,413, cross-linked starch was prepared by phosphorylation of starch using a variety of inorganic phosphates including sodium metaphosphate, polyphosphate, hexarnetaphosphate, and pyrophosphate. The reaction mixture has to be heated to 100 - 160°C for cross-linking of the starch molecules.

[0016] in U.S. Patent 4,098,997, an acetal cross-linked starch was prepared by reacting a granular starch with a propioiate ester at pH 6,5 - 12.5 at a temperature of 5°C to 60°C for 0.2 - 24hr, of which linkage can be readily removed under acidic conditions,

[0017] In European Patent EP 079686S B l , a high viscosity waxy potato starch was obtained by using typical crosslinking agents.

[0018] In PCX Patent Application Publication WO 2006/1 33335 A2, a reversibly swellable granular stareh-lipid was disclosed that included typical crosslinking agents, such as phosphorylating agents or epichlophydrin, to interact with the lipid.

[00 J 9] Large amounts of water are often needed to wash away the chemical residues or other impurities resulting from typical starch stabilization using chemicals. It is common that some chemicals used for treatment remain in the treated starch after washing.

[0020] The food industry prefers not to use chemicals to stabilize starch in edible foods because of the residual chemicals that becomes part of the starch, and because often residual chemicals remain.

[0021] Starch also has been stabilized by combining a starch with other natural products,

[0022] European Patent EP 0030448 B l discloses a method for fortifying foods with a sulfur-containing free amino acid dispersed in a liquid or softened plastic fat or oil [0023] PCX Patent Application Publication WO 2003/102072 Al discloses a method to stabilize starch against decomposition by combining a lipid, such as an individual fatty acid, with starch.

[0024] Native or added proteins when added to starch are known to change starch properties.

[0025] The effects of free amino acids addition to starch functional properties are known to have limited effects on starch. (Xiaonting Liang (2001); '"Effects of Lipids, Amino Acids, and Beta-Cyclodextrin on Gelatinization, Pasting, and Retrogradation Properties of Rice Starch;" Unpublished Doctoral Dissertation; Louisiana State University; Baton Rouge, LA, USA): (Xiaoming Liang and Joan M. King; "Pasting and Crystalline Property Differences of Commercial and solated Rice Starch With Added Amino Acids;" Journal of Food Science; 2003; Pages 832 ■- 838; Volume 68, Number 3; institute of Food Technologies (IFT); Chicago, IL, USA); (S. Lockwood, J. M. King and D. R. Labonte; "Altering Fasting Characteristics of Sweet Potato Starches Through Amino Acid Additives;" Journal of Food Science; 2008; Pages 373 - 377; Volume 73; Number 5, Institute of Food Technologies ( FT); Chicago, IL, USA), and (Azusa Ito, Makoto Hattori, Tadashi Yoshida, Keiji Yoshimura and Koji Takahashi; "Contribution of Charged Amino Acids to Improving the Degraded Viscosity of Potato Starch Paste by a Retort Treatment and During Storage;" Journal of Applied Glycoscience; 201 1 ; Pages 79 - 83; Volume 58; Number 3; Japanese Society of Applied Glycoscience; Tokyo, Japan).

[0026) Addition of charged free amino acids, such as lysine and monosodium giutamate, to starch resulted in inhibited peak viscosity and collapse of potato starch granules at pH 7 under retort treatment. (Azusa I to, Makoto Hattori, Tadashi Yoshida and Koji Takahashi; "Contribution of the Net Charge to the Regulatory Effects of Amino Acids and e-Poiy( _L - lysine) on the Gelatinization Behavior of Potato Starch Granules;" Bioscience, Biotechnology, and Biochemistry; 2006; Pages 76 - 85; Volume 70; Number 1 ; Japan Society for Bioscience, Biotechnology and Agrochemistry; Tokyo, Japan).

[0027] While lysine was found to depress starch breakdown for orange-fleshed sweet potato starch and white-fleshed sweet potato starch, it caused a higher breakdown value in rice starch as compared to starch with no additive. (Rosaly V. Manalis (2009); "Modification of Rice Starch Properties By Addition of Amino Acids at Various pH Levels;" Published Master Thesis; Louisiana State University; Baton Rouge, LA, USA). [Θ028] Different roles of aspartic acid and lysine additives were found in sweet potato in changing pasting stability. (S, Loekwood, J. M. King and D. R. Labonte; "Altering Pasting Characteristics of Sweet Potato Starches Through Amino Acid Additives;" Journal of Food Science; 2008; Pages 373 - 377; Volume 73; Number 5, Institute of Food Technologies (IFT); Chicago, IL, USA),

[0029] Lipids, such as free fatty acids, mono-,di- and tri-glycerides, have been used in food applications for different purposes. A main function of lipid, tor example, monogiyceride and sodium stearoyl lactylate, in starchy food is to retard finning and staling, which is related to inhibited starch retrogradation.

[0030] However, no one has combined starch, free amino acids and individual fatty acids, Surprisingly, we discovered that unexpectedly high stability was afforded to starch by combining starch with free amino acids and individual fatty acids, in excess of the expected additive effect of these additions.

BRIEF SUMMARY OF INVENTION

[ΘΘ31] In this invention, n at i v e starches were mixed with indivi dual fatty acids and free amino acids.

[( 032] The native starches comprise rice starch, potato starch, corn starch, wheat starch, tapioca starch, oat starch, barley starch, and waxy maize starch.

[0033] The free amino acids comprise lysine, glycine, gluiamine, aspartic acid, leucine, tyrosine, and cysteine,

[0034] The individual fatty acids comprise stearic acid, palmitic acid, linoleic acid, linoienic, and oleic acid,

[0035] The resulting novel starches exhibited increased pasting temperature decreased breakdown values and less retrogradation, when compared to native starch.

BRIEF DESCRIPTION OF DRAWINGS

[0036] Fig. 1 is a Differential Interference Contrast Microscope photograph of stained RVA heat treated samples without additional heating. [0037] Fig.2 is a Differentia! interference Contrast Microscope photograph of stained RVA heat treated samples which have undergone additional heating.

[0038] Fig.3 is RVA curves of rice starch untreated and treated with stearic acid and amino acids.

DETAILED DESCRIPTION OF INVENTION

[0039] In this invention, starch product with low breakdown and good stability at refrigeration temperature was created by adding a combination of an individual fatty acid, for example, stearic acid, and a free amino acid, for example, glycine, lysine, giutamine or cysteine to granular native starch.

[0040] The pH of a mixture comprising an individual fatty acid, a free amino acid and starch was adjusted to a value between 8- II, preferably to pH 10, using sodium hydroxide if necessary. The mixture was then slurried,

[0041] For treated rice starch, the individual fatty acid concentration was maintained between about 0.1% and 1.5%, with a preferred range between about 0.2% to 1.0% percent. The concentration of the free amino acids was maintained between about 1%- 6%. with a preferred range between 2% - 4%, Both individual fatty acid and free amino acid concentrations were on a starch dry weight basis.

[0042] The individual fatty acids comprise stearic acid, palmitic acid, linoleic acid, linoienic, and oleic acid,

[0043] The free amino acids comprise lysine, glycine, giutamine, aspartic acid, leucine, tyrosine, and cysteine.

[0044] Rapid visco analyzer ("RVA") was used to mimic heating and shearing condition, which includes a controlled heat-hold-cool temperature cycle. Each sample was held in an aluminum canister at 50 °C for 10 sec, with a stirring speed of about 9603pm, The stirring speed was then reduced to about 160rpm as the temperature of the mixture was increased at a rate of 12°C/min until the temperature of the mixture reached approximately 95°C, The mixture was maintained at about 95°C for about 2.5min. Then, the canister was cooled to 50°C at a rate of -12°C/min. During the entire heating and cooling process, the stirring speed was kept at 160rpm. [ΘΘ45] The novel starch mixtures were then dried by freeze-drier in accordance with conventional procedures and then milled into powders for storage,

EXAMPLE 1: Method for producing rice starch product of low breakdown by adding fixed asrs osnit of stearic acid as?d variable amou nts of lysine

[0046] Rice starch was purchased from Sigma Chemical Co. (S7260), By proximate analysis, this "batch of rice starch had 11 ,7% moisture, 0.20% lipid, 0.70% protein. There was 24,9% amylose based on dry rice starch weight.

[0047] To prepare a starch product with low breakdown, 2.9! g the rice starch was mixed with 0.4% stearic acid (on a starch dry weight basis) and to that was added lysine ranging i n co nc e ntrat i o n from 2% ~ 6% (on a starch dry weight basis). About 25g distilled water was added to the starch additive mixture in order to reach a final starch slurry of approximately 28g, The slurry had a pH of abo ut 1 0. Pasting characteristics of the starch slurries were tested by RVA analysis, wherein the Peak Viscosity (Peak), minimum viscosity (MV), final viscosity (FV), pasting time (Ptime) and pasting temperature (Ptemp) were measured. Further, breakdown (BKD) and total setback (TSK) were calculated, and all viscosity data reported in centipoise (cP),

[0048] R ice starch that was treated by add ing both stearic acid and lysine showed increased pasting temperature, from 83 to 91 C, and postponed peak time from 6.87 min to 7.96 min when compared to the control, untreated rice starch (See Table 1).

[0049] It appears that treatment of native rice starch caused starch to resist swelling and pasting. The breakdown value for the treated starch dropped from 241 cP for commercial starch to 71 cP for starch with 0.4% stearic acid and 6% lysine added. These changes in the starch characteristics when treated with stearic acid and lysine would appear to enhance cooking stability of rice starch. See Table 1 below for results for varying concentrations of stearic acid and lysine.

/ TABLE 3. Effects Of 0.4% Stearic A cid A nd 2%, 4% And 6% Lysine At Different Concentration On P asting Properties Of Commercial Rice

Stearic

Lysine Peak BKD Ptime Pterap TSB Acid M V (cP) FV (cP)

(%) (cP) (cP) (min) (°C) (cP)

0 0 2372.33b 2131.67b 240.67a 3112.00b 6.87c 83.15c 980.33a

0.4 2 2517.33a 2424.33a 93.00b 3425.67a 7.58b 88.92b 1001.33a

0.4 4 2507.67a 2431.00a 76.67bc 3458.67a 7.82ab 89.22ab 1027.67a

0.4 6 2506.33a 2435.33a 71.00c 3331.67a 7.96a 93.28a 896.33a

FA - fatty acid; MV · minimum viscosity; BKD - breakdown; FV - final viscosity; Ptemp temperature; Ptime - peak time; TSB - total setback.

The levels are based on starch dry weight.

Values followed by the same letter in the same column are not significantly different (P > 0.05).

EXAMPLE 2: Starch with fixed amouist of l sine and varying amounts of stearic acid added showed highly restricted swelling and pastmg properties,

[0050] The concentrations of stearic- acid of 0.4%, 0.6%, 0.8. a n d 1 .0% were added to rice starch, along with lysine at 6%. The preparation for starch mixture was the same as described above in Example 1. The starch slurry was at approximately pH 10. Pasting characteristics of the above starch slurries, including starch control, starch with added 0.4% stearic acid and 6% lysine, starch with added 0.6% stearic acid and 6% lysine, starch with added 0.8% stearic acid and 6% lysine, and starch with added 1.0% stearic acid and 6% lysine were tested by RVA analysis. The results are shown irs Table 2.

Table 2. Effects Of 0.4%, 0.6%, 0,8% And 1.0% Stearic Acid Asd 6% Lysine

Combinatio On Fasting Properties Of Commercial Rice

Values folio wed by the same letter in the same column are not significantly different [0051] As shown in Table 2, when lysine was kepi at 6%, addition of higher concentrations of stearic acid, 0.4%, 0,6%, 0,8% and 1.0 %, produced a starch slurry with average peak viscosities ("Peak") of 2506.33 cP, 2198,67cP, 1685.67cP and 123 ] .67cP, respectively.

[0052] Peak time values ("Ptiroe") for each treated starch slurry were significantly delayed when compared to control. The treated starch slurries showed that as the amount of stearic acid increased, the viscosity of the slurry ("Peak", "MV", and "FV") decreased. Lower viscosities typically indicate a high degree of cross-linking, while higher viscosities typically indicate a !ow cross-linking degree. The degree to which starch swelling ("Peak") is restricted, appears to be proportional with concentration of stearic acid for the concentrations examined. Total setback ("TSK"), which indicates potential for retrogradation of the starch, decreased with increased stearic acid added in the presence of 6% lysine.

[0053] Mixing of starch with a combination of free amino acids and individual fatty acids convert the starch into a starch thai resembles a chemically treated cross-linked starch.

EXAMPLE 3: Microscopic observation for rice starch product with stearic acid asd lysine as additives

[0054] A microscopic comparison was made between rice starch (control), rice starch with 6% lysine added, rice starch with 1% stearic acid added, and rice starch with 6% lysine and 1% stearic added,

[0055] The slurries were pre pared by R VA heat treatment as d e s cribed i n Examp l e 1 . The d ried starc h p ro d u ct s were milled and screened with a 0.5 mm screen in a Cyclone Sample Mill (tidy Corp., Port Collins, CO).

[0056] Mixtures of 3% starch slurries were prepared from each of the four freeze-dried rice samples described above, and each mixture was stirred for approximately 2 hrs. Each mixture was divided with one half of each starch mixture re-heated at 90°C for 20 min to cheek their heating stability; the other half was not heated. All starch mixtures, four mixtures both heated and isn~heated, were stained using 2% T ₂ -KT solution (0.2 g T and 2 g KI in 100 ml distilled water). The starch mixtures that had not been re-heated were designated Dl, D2, D3 and D4 respectively. The starch mixtures that were re-heated were designated HI, H2, H3 and H respectively. The stained samples were photographed using differential interference contrast microscopy (Leica DM RXA2), The results for the before-heating examples are shown in Figure 1.

[0057} Figure 1 showed that starches with additives exhibited different degrees of rupture after preparation by RVA heat treatment. In rice starch control (Dl), swollen starch fragments ( 1 ) can be observed, indicating rupture of starch granules and development of starch gels (3). These starch fragments ( 1 ) became even cloudier in rice starch with added 6,0 % lysine (D2), suggesting, though this explanation is not required for this invention, that there was an increase in the amount of amylose leached (3 ) from the starch granules. This explanation was consistent with the result of escalated breakdown of starch with lysine added during the RVA heat treatment caused by rapid starch granule rupture,

(0058] In rice starch treated with 1.0% stearic acid (D3), starch granules ( 1 ) showed shape with more clarity than starch with added 6.0% lysine (D2). it would appear that the addition of stearic acid caused less starch granule rupture.

0059] In rice starch treated with 1.0% stearic acid and 6.0% lysine (D4), far more intact swollen starch granules (7) were observed. This serves as strong evidence that addition of both 1.0% stearic acid and 6,0% lysine inhibited starch pasting by keeping swollen starch granules structure from rupturing,

[006Θ] Figure 2 displays the microphotograpbs of the rice starch and rice starch with additives after heating.

[0061] Rice starch heated (HI) and rice starch heated with either lysine or stearic acid (112 and H3, respectively) displayed increased amylose leaching, giving more blurred and fuzzier starch granule shape than unheated samples. The starch in HI shows significant amounts of starch gel (3), Addition of the lysine (H2) shows few starch granules and with more starch gel (3). The addition of stearic acid (H3) appears to result in more distinct swollen granules (1 ) as well as starch gel (3), Surprisingly, the shape of rice starch granule with both stearic acid 1 ,0% and lysine 6.0% (H4) added remained intact (7). Since neither starch treated with either a free amino acid nor an individual fatty acid alone produced stable starch granules, it was surprising that the combination of a free amino acid and an individual fatty acid would have such a dramatic, effect.

[0062] The novel starch comprising native starch, a free amino acid, and an individual fatty acid appears to be heat-resistant and resistant to swelling and pasting. While not requiring this explanation for the invention, it appears that the reduced peak viscosity found in native starch treated with 1.0% stearic acid and 6.0% lysine, was caused by inhibited starch swelling, rather than starch hydrolysis.

EXAMPLE 4: Starch with highly restricted swelling assd pasting properties by

stearic acid and other free ammo acids addition

[0063] Rice starch was mixed with 1% stearic acid and 6% glycine, glutamine, or cysteine (starch dry weight basis). The sample preparation was the same procedure as described in Example 1 above. The pH of the starch slurry was adjusted to 10 by sodium hydroxide, Pasting characteristics of the above starch samples were tested by RVA analysis as Example 1.

[0064] Similar to lysine, addition of both 6.0% glycine and 1.0% stearic acid at pH 10 showed inhibited starch pasting, lire trough of its RVA curve disappeared and its highest viscosity was only 10.6% of the peak viscosity of starch control The time to reach peak viscosity was postponed 1.5 min, compared to starch control. Cysteine and glutamine addition both demonstrated similar inhibited starch pasting as glycine. The degrees of inhibited swelling for cystein e an d gl utam ine were even higher than that of lysine. Because of their unique pasting curves, peak viscosity, minimum viscosity, and breakdown values c o u l d n ot be obtained. Results are shown in Figure 3, where viscosity is plotted against time for rice starch untreated and treated with 1.0% stearic acid and 6,0% amino acids. The amino acids included glutamine, cysteine, glycine and lysine.

EXAMPLE 5: Treated Starch Leads to Reduction in Reirogradation

[0065] The samples were prepared as described in Example 3. The samples including ( 1 ) rice starch control, (2) rice starch with 6% lysine added, (3 ) rice starch with 1.0% stearic acid added, and (4) rice starch with both 1 ,0% stearic acid and 6% lysine added, Individual fatty acids and free amino acids were added on a starch dry weight basis. All samples were examined using RVA heating cycles as described in Example 1 above. Th e starch products were freeze-dried and then milled with a 0.5 mm screen in the Cyclone Sample Mill (Udy Corp., Port Collins, CO).

[0066] Twenty mg of distilled water was added to 1 Omg of each of these starch samples in pans. The samples were then sealed and stored at room temperature overnight for starch hydration. The pans were heated in a differentiai scanning calorimeter (DSC) beginni ng at 15 °C and then increasing the temperature to 140 °C at a rate of 5 °C /mm. After the above DSC tests, pans were cooled to room temperature, and then refrigerated at 4 ± 1 °C for lO days. The starch samples were removed from the refrigerator and allowed to remain at room temperature for 2 hrs. Another pan containing 20 ml distilled water was used as a reference. The thermal transition parameters, including enthalpy (J/g), onset temperature and peak temperature were determined.

[0067 j The degree of starch retrogradation was calculated as follows:

% retrogradation = 100*[ ΔΗ1/ ΔΗ2]

where ΔΗ1 is the enthalpy change of the thermal transition for retrograded starch and ΔΗ2 is the enthalpy change for the thermal transition of starch geiatinization,

Table 3, Retrogra atiors Of Selected RVA Treated Samples After 10 Days

Refrigeration Storage

Sample (RVA heated) Starch-Lipid Complex Form Retrogradation Peak

ToCQ TpfC) ΔΗ (J/g) To (°C) Tp (°C) ΔΗ (J/g) Percentage

Control Rice Starch n/a n/a n/a 43,84 53.34 ■1.99 ■1 1 .38

Added 100.46 1 10.13 2,08 45.24 53.75 1 .60 13.27

Control Starch is Starch Without Any Additive

[0068] Retrogradation peak was found in samples after being stored for 10 days under refrigeration. It is widely accepied that starch retrogradation under long time storage is caused by amyiopectin crystallization, which can be measured by DSC in a temperature range of 40 - 100°C. The peak temperature fo r th e s ta rc h s am p l e s ranged from 51. PC to 58.8 ^C C.

[0069] The geiatinization temperature of raw rice starch is about. 20° higher than the valises obtained from the DSC, indicating a less ordered and less perfect starch structure for the treated starches than found for native starch granules. [0070] The addition of lysine and stearic acid to native starch caused the retrogradati on e nth a l py to be lower than the retrogradation peak for the control starch,

[ΘΘ71] Starch treated only with lysine was not as effective in lowering the retrogradation enthalpy.

[0072] Starch treated only with stearic acid was not as effective in lowering the retrogradation enthalpy.