WO2019123135A1

WO2019123135A1 - Method for producing a turmeric-based oil solution for food use

Info

Publication number: WO2019123135A1
Application number: PCT/IB2018/060004
Authority: WO
Inventors: Tullia GALLINA TOSCHI; Mara MANDRIOLI; Enrico VALLI; Federica SGARZI; Valentina SERRA; Fausto Merli
Original assignee: Alma Mater Studiorum - Universita' Di Bologna; Oleificio Zucchi S.P.A.
Priority date: 2017-12-20
Filing date: 2018-12-13
Publication date: 2019-06-27
Also published as: EP3727036A1

Abstract

A method for producing a turmeric oil solution for food use, comprising the following steps: selecting a turmeric powder, on the basis of the total amount of curcuminoids active principles contained in said powder; adding said turmeric powder to a high oleic sunflower oil, said high oleic sunflower oil containing at least 80% of oleic acid on the total of fatty acids, so as to obtain a 0.5: 10 ratio between said turmeric powder and said high oleic sunflower oil; subjecting said turmeric powder and said high oleic sunflower oil to stirring, so as to obtain a mixture comprising said turmeric powder and said high oleic sunflower oil; filtering said mixture, so as to remove said turmeric powder and obtain said turmeric oil solution. A turmeric oil solution for food use comprises a high oleic sunflower oil, said high oleic sunflower oil containing at least 80% of oleic acid on the total of fatty acids, and a total predetermined amount of curcuminoids active principles. Said oil solution is provided with a resistance to the forced oxidation that is at least 10% higher than the resistance to the forced oxidation of a high oleic sunflower oil as sampled, said resistance to the forced oxidation being measured in hours and determined through evaluation of the oxidative stability index (OSI) at 110°C.

Description

Method for producing a turmeric-based oil solution for food use

[0001] The invention relates to a method for producing a turmeric-based oil solution (so- called“turmeric oleolite”) for food use, in particular a method for producing a turmeric oil solution that is usable for seasoning, cooking and/or frying food products. The invention can be applied industrially in the sector of the production of vegetable oils.

[0002] The name“turmeric” identifies the species Curcuma longa L., herbaceous plant belonging to the family of Zingiberaceae and original from south-eastern Asia. The turmeric, and more exactly the turmeric powder (yellow-orange coloured powder, obtained from the boiled and dried rhizomes of the plant), is used in the cookery as an aromatizing agent (spice). The active principles contained in the turmeric powder are named curcuminoids and comprise the following molecules (having a linear diarylheptanoid structure): curcumin, bisdemethoxycurcumin and demethoxycurcumin. Curcuminoids active principles have been studied for their properties, in particular for the antioxidant activity and the antiradical activity, tested experimentally and fully documented in the scientific literature.

[0003] The presence of the aforesaid active principles thus makes it substantially advantageous and desirable to introduce the turmeric powder into the human diet. However, the oral intake of the turmeric powder may be scarcely easy and/or pleasant for many of the potential users. The use has been thus proposed of food oils, for example soyabean oil, ( Asnaashari , E., Asnaashari, M., Ehtiati, A. et al. Comparison of adaptive neuro-fuzzy inference system and artificial neural networks (MLP and RBF)for estimation of oxidation parameters of soybean oil added with curcumin. Food Measure (2015) 9: 215 ) or sunflower seed oil ( Semwal , A.D., Sharma, G.K., Arya, S.S. Antioxygenic activity of turmeric (Curcuma longa) in sunflower oil and ghee. Journal of Food Science and Technology (1997) 34 (1), pp. 67-69), as suitable vehicles for the oral administration of curcuminoids active principles. A food oil supplemented with curcuminoids active principles (extracted chemically from turmeric powder) can in fact be used as an alternative to a traditional food oil, both for raw seasoning (for example, for seasoning salads) and for cooking, in particular frying, food products.

[0004] A drawback of the aforesaid oils for food use supplemented with curcuminoids principles consists of the fact that these oils have, already originally, a substantially poor resistance to oxidation (oxidation that is caused by the heat treatments underwent by the oil during the cooking or frying step), which causes a significant deterioration of the fats present in the oil. [0005] Another drawback consists of the fact that, in the oils for food use supplemented with curcuminoids principles of known type, the titre of the active principles is not determined, with a consequent risk of making the oral intake of the oil scarcely effective for the consumer.

[0006] A further drawback consists of the fact that, in order to make an oil for food use supplemented with curcuminoids principles by using the known methods, it is necessary to extract with organic solvents the active principles from the dried rhizome. This makes producing the oil supplemented with extracted curcuminoids principles substantially costly and laborious, also for the need of disposing suitably of the solvents used for the extraction.

[0007] An object of the invention is to improve the known methods for producing oils for food use containing curcuminoids active principles.

[0008] Another object is to make available a method for producing an oil for food use containing curcuminoids active principles and provided with a suitable resistance to oxidation, a deterioration process that occurs, in particular, during a cooking or frying heat treatment.

[0009] A further object is to make available a method for producing an oil for food use containing curcuminoids active principles, in which the titre in curcuminoids active principles is substantially predetermined and high.

[0010] Still another object is to make available a method for producing an oil for food use containing curcuminoids active principles, which enables the need to extract the curcuminoids active principles by using solvents to be avoided.

[0011] A still further object is to make available an oil for food use containing curcuminoids active principles, in which the titre in curcuminoids active principles is substantially predetermined and high and which is provided with a suitable resistance to oxidation.

[0012] In a first aspect of the invention, a method is provided for producing a turmeric oil solution, as defined in claim 1.

[0013] In a second aspect of the invention, a turmeric oil solution is provided, as defined in claim 10.

[0014] Owing to these aspects, a method for producing a turmeric oil solution and a corresponding product (turmeric oil solution) are made available, which enable the previously mentioned objects to be achieved. [0015] In fact, the method according to the invention enables a turmeric oil solution to be produced that is usable as an oil for food use, which is provided with a suitable resistance to the oxidation during cooking or frying. Moreover, the method according to the invention does not require an extraction step with solvents and enables an end product to be obtained in which the minimum total amount in curcuminoids active principles is at least 500 ppm, this making the turmeric oil solution according to the invention able to carry a predetermined amount of curcuminoids active principles.

[0016] The Applicants could verify that by mixing high oleic sunflower oil - i.e. a sunflower seed oil with high oleic acid (Cl 8:1) content - and a turmeric powder containing a predetermined total amount of curcuminoids active principles it is possible to produce a turmeric oil solution (which can also be defined as“turmeric oleolite”) having peculiar properties.

[0017] In fact, the turmeric oil solution according to the invention is provided with a resistance to the forced oxidation that is greater than the resistance to the forced oxidation with which a high oleic sunflower oil is provided in the absence of curcuminoids active principles. In particular, it has been observed that the resistance to the forced oxidation exhibited by the turmeric oil solution according to the invention is greater than the resistance to the forced oxidation that could be expected because of the simultaneous presence of high oleic sunflower oil and curcuminoids active principles. Therefore, the Applicants hypothesised a new and surprisingly unexpected synergic effect due to the presence of curcuminoids active principles in a total amount of at least 500 ppm in a high oleic sunflower oil.

[0018] The invention can be better understood and implemented with reference to the attached drawings which illustrate an embodiment thereof by way of non- limiting example, in which:

[0019] Figure 1 is a chromatogram relating to the chromatographic elution of a standard solution mixture of curcumin, bisdemethoxycurcumin and demethoxycurcumin;

[0020] Figure 2 is a chromatogram relating to the chromatographic elution of a sample of oil solution according to the invention;

[0021] Figure 3 is a graph illustrating the outcomes of an analytical evaluation of the total antioxidant activity of the phenol fraction in samples of oil solution according to the invention and in samples of high oleic sunflower oil; [0022] Figure 4 is a graph illustrating the outcomes of a further analytical evaluation of the total antioxidant activity of the phenol fraction in samples of oil solution according to the invention and in samples of high oleic sunflower oil.

[0023] In the context of the present description and of the attached claims:

the terms“curcuminoids”,“curcuminoids active principles” and“active principles of the turmeric” are considered to be synonyms and are used interchangeably;

the terms“turmeric oil solution” and“turmeric-based oil solution” are considered to be synonyms and are used interchangeably;

the terms“high oleic sunflower oil” and“sunflower seed oil with high oleic acid content” are considered to be synonyms and are used interchangeably;

the terms“high oleic sunflower oil” and“sunflower seed oil with high oleic acid content” define a sunflower oil that contains at least 80% of oleic acid on the total of fatty acids.

[0024] The turmeric oil solution according to the invention has been obtained by the Applicants by mixing a high oleic sunflower oil, i.e. a sunflower oil containing at least 80% of oleic acid on the total of fatty acids, and a selected turmeric powder, with a 0.5:10 (w/w) oil / turmeric powder ratio. The mixture of oil and turmeric powder is produced by stirring (for example through rocking stirrer and at a speed of 250 oscillations/minute) at a temperature comprised between 40°C and 60°C for at least 24 hours in a closed system saturated with inert gas, in particular nitrogen (for example, a container with a sealing stopper and a headspace saturated with nitrogen). The turmeric powder has been selected on the basis of the total content thereof in curcuminoids active principles (curcumin, bisdemethoxycurcumin and demethoxycurcumin). In particular, a turmeric powder has been used containing from 2.22% to 2.85% in curcuminoids active principles. The mixture of oil and turmeric powder thus obtained has been subsequently filtered, obtaining an oil solution that is clear and devoid of suspended material. The filtering step can be performed by using known methods and devices and can comprise, for example, a filtration by gravity onto a paper filter.

[0025] If the method according to the invention is implemented on plant pilot scale or on industrial scale, it is possible to use devices and apparatuses that are known to the person skilled in the art. For example, the stirring step can be performed in a tank that is of suitable capacity and is equipped internally with a motorized mechanical stirrer (for example, a blade stirrer). In order to perform the stirring step at the required temperature, the tank can be provided with a heating gap or liner, which can be supplied with a suitable heating fluid (for example, water), as well as with one or more thermometric probes for the control of the temperature. In order to perform the stirring step in a closed system saturated with an inert gas, the tank can be equipped with a sealing lid, with safety valves and with a tube for the bubbling of nitrogen into the mixture being stirred. In order to perform the filtering step, it is possible to use, for example, an alluviation filter.

[0026] On the basis of what has been set out above, in the method according to the invention the following steps can thus be identified:

a) Selection of a turmeric powder, on the basis of the total content thereof in curcuminoids active principles;

b) Addition of the selected turmeric powder to a high oleic sunflower oil, so as to obtain a ratio equal to 0.5:10 between the turmeric powder and the high oleic sunflower oil;

c) Stirring (for at least 24 hours and at a temperature comprised between 40°C and 60°C) in a closed system saturated with an inert gas, in particular nitrogen, so as to obtain a mixture comprising the turmeric powder and the high oleic sunflower oil;

d) Filtration of the mixture, so as to remove the turmeric powder and obtain a turmeric- based oil solution.

[0027] The finished product (turmeric oil solution) has been subsequently analyzed by the Applicants. In particular, the total content in curcuminoids and the resistance to the forced oxidation have been determined. The latter is measured in hours and is determined through evaluation of the oxidative stability index (OSI) at H0°C. Through the experimental evaluation disclosed above, in the turmeric oil solution according to the invention a significant increase in the resistance time to the forced oxidation was observed with respect to the high oleic sunflower oil not mixed with the selected turmeric powder. Moreover, by using an RP-HPLC analytical method (disclosed in detail below) a total amount of curcuminoids active principles of at least 500 ppm was measured, which attests good levels of solubilization of the total curcuminoids active principles in the turmeric oil solution according to the invention.

[0028] By way of non-limiting example, the following are disclosed below: a procedure for determining analytically the total content in curcuminoids in a turmeric oil solution according to the invention (Example 1); a procedure for evaluating experimentally the oxidative stability index of a turmeric oil solution according to the invention (Example 2); a procedure of evaluation of raw materials that are usable in the method according to the invention (Example 3); a procedure for the preparation in laboratory of a turmeric oil solution according to the invention (Example 4); outcomes of analyses conducted on prototypes of turmeric oil solution according to the invention (Example 5); outcomes of analytical comparisons between a turmeric oil solution according to the invention and samples of high oleic sunflower oil (Example 6); considerations emerging from the experimental plan prepared and implemented by the Applicants (Example 7).

[0029] Example 1 - Analytical determination of the total content in curcuminoids

[0030] The total content in curcuminoids of the turmeric oil solution according to the invention has been determined analytically by RP-HPLC (high performance liquid chromatography in reverse phase). The extraction of the curcuminoids active principles is carried out with methanol, according to what is indicated by M. Paramasivam ( M . Paramasivam, R. Poi, H. Banerjee, A. Bandy opadhy ay: High-performance thin layer chromatographic method for quantitative _determination of curcuminoids in Curcuma longa germplasm. Food Chem. 113, 640-644, 2009). In particular, lg of turmeric oil solution is weighed and the extraction is carried out by adding 10 ml of methanol, stirring the mixture of oil solution and methanol through vortex (model ST5, Janke & Kunkel, Germany) for 1 minute, placing the mixture in an ultrasound bath (Branson 2510) for 15 minutes, centrifuging (ALC PK 120 model, ALC, Italy) and repeating the extraction another 2 times in the same mode. The collected methanol fractions are gathered and dried with rotating evaporator (Rotavapor, Buchi R-200). The residue is dissolved in methanol, brought up to the appropriate volume to obtain the optimum concentration necessary for chromatography injection and filtered with a 0.45 pm nylon filter (Phenomenex). The method for the chromatographic determination is the one, appropriately modified, suggested by R. Li (Rui Li, Cheng Xiang, Min Ye, Hui-Fang Li, Xing Zhang, De-An Guo: Qualitative and quantitative analysis of curcuminoids in herbal medicines derived from Curcuma species, Food Chemistry 126 (2011) 1890-1895). 10 pL of extract were injected into a HPLC HP 1100 Series system (Hewlett-Packard, Germany), equipped with: 1260 Infinity quaternary pump (Agilent Technologies, USA), Kinetex 5p C18 100 A 150 x 4.60 mm column (Phenomenex), 1100 Series self-sampler (Agilent Technologies, USA), 1050 Series UV-VIS photodiode detector (Hewlett-Packard, Germany), and a ChemStation acquisition software (Rev.A.08.03 Agilent Technologies, USA). The instrumental conditions were as follows: eluent mixture A consisting of 100% acetonitrile; eluent mixture B consisting of water with 0.1% formic acid (w/v); elution of the mixtures at a flow of 0.4 ml/min according to the gradient shown in the following Table 1:

The signal is monitored through a photodiode detector, at a 420 nm wavelength. The quantification of the curcuminoids active principles is then carried out with the method of the external standard, through the construction of calibration curves obtained by evaluating solutions with known concentration of analytical standards of pure curcumin for analysis (Sigma-Aldrich, Steinheim, Germany), bisdemethoxycurcumin (>98%-HPLC_Sigma- Aldrich, Steinheim, Germany) and demethoxycurcumin (>98%-HPLC Sigma-Aldrich, Steinheim, Germany). Figure 1 shows a chromatogram (indicated by the letter A) relating to the chromatographic elution of a standard solution mixture of curcumin (CU), bisdemethoxycurcumin (BDMC) and demethoxycurcumin (DMC). Figure 2 shows a chromatogram (indicated by letter B) relating to the chromatographic elution of a sample of oil solution according to the invention (CU = curcumin; BDMC = bisdemethoxycurcumin ; DMC = demethoxycurcumin).

[0032] Example 2 - Experimental evaluation of the oxidative stability index (QSI)

[0033] The stability against the oxidation, or oxidative stability index (OSI), of a turmeric oil solution according to the invention has been evaluated experimentally by measuring the so-called Osi-Time. The oxidative stability is determined by subjecting the oil solution to a forced oxidation, which is induced through heating and bubbling of air in standardized conditions. A tool of known type is used, in which the tested oil solution is heated to H0°C in the presence of a continuous flow of air having a speed of 150 ml/min. In this manner the end products of the oxidation step, above all organic acids such as formic acid, are induced first to volatilize and then to solubilize in bidistilled water. The resistance to the oxidation is determined by an electrode, which measures the variations in conductivity of the deionized water in which the air flow arrives that contains the volatilized substances. Through this measurement that is carried out continuously, the instrument extrapolates, from the initial step of the oxidation to the step in which the oxidation takes on an exponential trend, the datum relating to the induction period, expressed in hours and hundredths of hours and named as Osi-Time ( Jebe , Matlock, Sleeter, 1993: Collaborative study of the Oil Stability Index Analysis. - JAOCS, Vol. 70, 1055-1061). The instrument (OSI-8, produced by Omnion Scientific Instruments under licence from Archer Daniels Midland Co.) has 8 housings that are thermostated at H0°C, in each of which a glass sample-holding tube can be inserted that contains 5 ± 0.1 g of oil to be tested. Air is blown into each tube at a flowrate of 150 ml/min. Each tube containing the sample is connected to a polycarbonate tube containing 50 ml of bidistilled water, in which the volatile substances are bubbled that are formed during the oxidation of the lipid matrix of the oil solution and which are conveyed by the air flow. Inside the polycarbonate tube the electrode is contained by means of which it is possible to measure continuously the variation in conductivity of the bidistilled water. Alternatively to the measurement of the Osi-Time, it is possible to use another method that is based on the forced oxidation, which is named as AOM (Active Oxygen Method) and is standardized (AOCS Standard Method Cd-l2-b92).

[0034] Example 3 - Evaluation of raw materials to be used in the method according to the invention (high oleic sunflower oil; turmeric powder)

[0035] An analytic evaluation has been made of the raw materials to be used in the method according to the invention, i.e. high oleic sunflower oil and turmeric powder. For turmeric, three different typologies of dried powdered turmeric (provided by three different Manufacturers) were evaluated, in which both the content of total curcuminoids and the quantity of each single curcuminoid - bisdemethoxycurcumin (BDMC), demethoxycurcumin (DMC) and curcumin (CET) - were quantified. From the obtained results, it is inferred that BDMC, DMC and CU are present in the evaluated samples, but in very different amounts. In different turmeric powders, above all different BDMC and DMC contents are pointed out, with an always prevalent presence of CU. The values of the total curcuminoids varied, in the three analyzed powders, from 1.21% to 2.85% and the results obtained from the analyses carried out (RP-HPLC according to the aforesaid method of R. Li et al. (2011), modified) are shown in detail in the following Table 2:

[0036] Table 2

Following the obtained results, the powders of turmeric belonging to the Curcuma longa L. species were selected in order to produce the turmeric oil solution according to the invention and in the preparation of prototypes of turmeric oil solution the two typologies of powder corresponding to Sample 2 and Sample 3 of Table 2 have been used, namely the two samples containing the greatest quantity of total curcuminoids.

[0037] Example 4 - Preparation in laboratory of a turmeric oil solution according to the invention

[0038] 2 kg of high oleic sunflower oil have been mixed with the quantity of turmeric powder necessary for complying with the drug-oil ratio to be compared (0.5:10) in a steel container having a 3.5 litre capacity. The container was provided with an inlet for inert gas (nitrogen), with valve and tube suitable for enabling the gas to bubble into the mixture and subsequent production of a closed system saturated with inert gas. The container has been placed on an Arex-X (Velp Scientifica) heating plate provided with a VTF digital thermoregulator with Pt100 steel probe (temperature range -10 - +300 °C, resolution 0.2 °C, accuracy + 0.5 °C) for the control and the thermostating of the temperature. The temperature has been set at 60°C. The oil solution of turmeric powder has been kept under constant stirring for 48 h, through a DLH model (Velp Scientifica) rod mechanical stirrer at 370-450 rpm. Once completed the stirring step, the turmeric oil solution has been filtered by gravity onto a paper filter.

[0039] Example 5 - Analysis of prototypes of turmeric oil solution according to the invention

[0040] On the produced prototypes of turmeric oil solution (obtained from Sample 2 and from Sample 3 of Example 3) the parameters of interest have been determined, namely the resistance to the forced oxidation and the total amount of curcuminoids active principles. The obtained results pointed out, in both the prototypes, significant increases in the resistance time to the forced oxidation (Osi-Time) and good levels of solubilization of total curcuminoids active principles in the oil, as shown in the following Table 3:

[0041] Table 3

oleic sunflower oil (HOS) upon receipt of the oil and“Osi-Time HOS” indicates the determination carried out on the high oleic sunflower oil on the date on which the prototype of turmeric oil solution has been produced. Sample 2 has exhibited an Osi-Time value of 23.15 h and a total curcuminoids content of 923.80 ppm, whilst Sample 3 has exhibited an Osi-Time value of 24.83 h and a total curcuminoids content of 810.62 ppm.

[0042] Example 6 - Analytical evaluation of the variation in the total antioxidant activity of the phenol fraction in a turmeric oil solution according to the invention and in samples of high oleic sunflower oil

[0043] In order to evaluate the total antioxidant activity of the phenol fraction in experimental samples (samples of turmeric oil solution according to the invention versus samples of high oleic sunflower oil), the 2,2-diphenyl- l-picryl-hydrazyl radical test has been used (DPPH·, C18H72N5O6) (Blois, 1958). DPPH· is a purple red coloured powder having the property of undergoing decolouration in the presence of an antioxidant agent. The degree of decolouration is proportionate to the antioxidant charge of the tested substrate (sample). The DPPH· test enables compounds to be detected that are able to transfer hydrogen or electrons and this is evaluated through the measurement of the decrease in absorbance at predetermined wavelength (l=492 nm) of a DPPH· radical solution after a reaction with a sample to be tested. The spectrophotometric reading of the absorbance is carried out at regular time intervals, for a total incubation time of 35 minutes. The results of the analysis are expressed as percentage of inhibition of the DPPH· radical. In order to avoid autoxidation processes, the samples are stored in the dark in a cool and dry place until the DPPH· test is carried out.

[0044] The following samples have been analyzed:

Sample of turmeric oil solution according to the invention, made by using a high oleic sunflower oil produced by the Applicant Oleificio Zucchi Spa (sample named as“FS” hereinafter);

Sample of high oleic sunflower oil as sampled (namely without turmeric) produced by Oleificio Zucchi Spa (sample named as FZ hereinafter);

First sample of high oleic sunflower oil as sampled that is commercially available and is not produced by Oleificio Zucchi Spa (sample named as FE hereinafter).

Second sample of high oleic sunflower oil as sampled that is commercially available and is not produced by Oleificio Zucchi Spa (sample known as FO hereinafter).

[0045] Mode for carrying out the DPPH· radical test

[0046] All the samples have been diluted by a dilution factor equal to 5 and subsequently seeded (each sample replicated 5 times) in a 96- well plate. The stock (10 mM) and working (100 mM) solutions of DPPH· have been prepared at the time of use. Two blank samples (Bl and B2) have been also prepared that contained only DPPH·. The plate was analyzed (namely, read) on the spectrophotometer at the wavelength l of 492 nm at regular time intervals and for a total time of 35 minutes. The analysis has been conducted blindly. In the case of the FS samples, given their intense yellow colour, in two sample wells only the diluted oils have been sown, at the same concentration as the others.

[0047] The measured absorbance values (O.D.) have been processed by using the following formula:

[0048] The aforesaid samples FO, FE, FS and FZ have been tested before undergoing heat treatment (namely, oil as sampled), at the end of the first frying step (specifically, once the temperature of l80°C was reached, the oil has been maintained at this temperature for a further 15 minutes) and after a second heating step (the samples have been maintained at l00°C for another 6 hours). Hereinafter, the three aforesaid times are respectively indicated as: tO, tl and tF.

[0049] The outcomes of the test are shown in the graph of Figure 3. The analytical data have been undergone variance analysis (ANOVA) and Bonferroni post hoc test and are shown in the graph as percentage of inhibition of the DPPH· radical (tO: ****p<0.000l FS vs FO, FE and FZ; ****p<0.000l FO vs FE and FZ; tl: ****p<0.000l FS vs FO, FE and FZ; ****p<0.000l FO vs FE and FZ; tF: ****p<0,000l FS vs FO, FE and FZ, ****p<0.000l FO vs FE and FZ).

[0050] The carried out analysis has pointed out that the FS sample (turmeric oil solution according to the invention) shows a significant antioxidant activity (>55%) at all the investigated experimental times (tO, tl and tF) and that such activity is as well significantly greater than that of all the other analyzed samples (p<0.000l). Moreover, although the FO sample (commercially available high oleic sunflower oil) shows a lower antioxidant activity than the FS sample (<20%), the FO sample is however provided with an antioxidant activity that is higher than that of the FZ and FE samples.

[0051] The variation in antioxidant activity over time has been further evaluated for each of the samples FS, FO, FE and FZ, which have been tested before, during and after frying (namely at the experimental times tO, tl and tF). [0052] The outcomes of the aforesaid evaluation are shown in the graph in Figure 4. The analytical data have been undergone analysis of variance (ANOVA) and Bonferroni post hoc test and are shown in the graph as percentage of inhibition of the DPPH· radical (FO: **p<0.0l tO vs tF; FE: **p<0.0l tO vs tF).

[0053] The obtained results have pointed out a good stability of both FS (turmeric oleolite) and FZ (high oleic sunflower oil as sampled produced by Oleificio Zucchi) samples, exhibiting statistically not significant variations before and after the frying process, whereas the FO and FE samples (high oleic sunflower oil as sampled found on the market) on the other hand have shown a significant variation (p<0.0l) in antioxidant activity before and after frying.

[0054] Example 7 - Considerations emerging from the experimental plan prepared and implemented by the Applicants

[0055] In the scientific and technological context that enabled the present invention to be achieved, an experimental plan has been prepared aiming to identify the most suitable process conditions for producing a turmeric oil solution (oleolite) provided with specific composition features and with an appropriate resistance to the forced oxidation.

[0056] In the aforesaid experimental plan, the effects have been evaluated that were obtained by varying the following process parameters:

i) concentration ratio between turmeric powder and high oleic sunflower oil (0.1:10; 0.5:10; 1.0:10);

ii) temperature (ambient temperature = 20-25°C; 40°C; 60°C; 80°C; l50°C);

iii) maceration time or contact time (namely, the time during which the turmeric powder is mixed with the oil by stirring) of the turmeric powder in the oil (24 h; 48 h).

[0057] As shown in Table 4 (total curcuminoids and resistance to the forced oxidation relating to the oil solutions having a contact time of 24 hours) and in Table 5 (total curcuminoids and resistance to the forced oxidation relating to the oil solutions having a contact time of 48 hours) shown below, the obtained analytical results pointed out that, in the oleolites produced at a temperature of l50°C and both with a maceration time of 24 h and with a maceration time of 48 hours, the high temperature causes an oxidative degradation, with consequent drastic reduction of the resistance to the forced oxidation compared to the initial values exhibited by the high oleic sunflower oil as sampled, and a degradation of the curcuminoid active principles present. In general, with the temperature increase an increase in the solubility of the curcuminoid active principles occurs. [0058] At a temperature of 80°C and at low concentrations of the turmeric powder (drug/oil ratios 0.1:10 and 0.5:10) a reduction of Osi-Time (namely, of the time of induction to the forced oxidation) has been almost always observed, whilst at a higher concentration of the turmeric powder (drug/oil ratio 1.0:10) an increase of the Osi-Time has been observed also at a temperature of 80°C, which is probably due to the high concentrations of curcuminoid active principles reached.

[0059] The results obtained by preparing the turmeric oleolite with a 0.1:10 drug/oil ratio and a maceration time of 24 hours (see Table 4) point out that the Osi Time decreases as the temperature increases: in fact, at 80°C and with a curcuminoid concentration of 312.05 mg/kg (ppm), a reduction in Osi-Time is observed that is equal to -26.19% compared with the initial value.

[0060] Again with reference to a 0.1:10 drug/oil ratio and to a maceration time of 24 hours (see Table 4), it is noted that the total curcuminoid concentration varies between 262.69 ppm and 314.48 ppm and that the greatest concentrations are obtained at the temperatures of 60°C and 80°C, without nevertheless reaching the concentration of at least 500 mg/kg mentioned in the application in subject (see in particular Table 3 of the previous Example 5).

[0061] On the other hand, as shown in Table 4 and Table 5, an optimum combination of increases in both the resistance to the forced oxidation (Osi-Time comprised between 20.15+0.21 h and 25.38+1.59 h) and the concentration of total curcuminoid active principles (concentration comprised between 973.78+3.09 ppm and 1470.14+18.27 ppm) has been obtained by setting specifically the process parameters, in particular by providing a 0.5:10 drug/oil ratio and a 40-60°C temperature range.

[0062] This demonstrates the presence of a synergic effect between temperature and drug/oil concentration ratios (thus content in curcuminoid active principles), with consequent significant increase in the resistance to the forced oxidation.

[0063] Table 4

Table 5

[0064] From the disclosure above, it can be stated that the method according to the invention enables a product based on turmeric powder and high oleic sunflower oil (turmeric oil solution) to be obtained that is suitable for human consumption, has a predetermined content (at least 500 ppm) of curcuminoids active principles (curcumin, bisdemethoxycurcumin and demethoxycurcumin) and is provided with a resistance to the forced oxidation that is at least 10% higher than the resistance to the forced oxidation of a high oleic sunflower oil as sampled (i.e. without addition of turmeric powder). The aforesaid resistance to the forced oxidation is intended as measured in hours and determined by evaluation of the oxidative stability index (OSI) at 1 l0°C.

[0065] In particular, in the turmeric oil solution according to the invention it is possible to point out a synergic action (between the curcuminoids active principles and the high content in oleic acid of the sunflower oil), which provides the turmeric oil solution with a significant resistance to the oxidation. The turmeric oil solution according to the invention is particularly stable against the oxidation and the thermal treatments, being thus suitable not only for the use as a food condiment, but also for cooking and frying foods.

[0066] Possible variations and/or additions to what has been described above and/or shown in the Figures are moreover possible.

Claims

1. Method for producing a turmeric-based oil solution for food use, comprising the following steps:

Selecting a turmeric powder, on the basis of the total amount of curcuminoids active principles that is contained in said powder;

Adding said turmeric powder to a high oleic sunflower oil, said high oleic sunflower oil containing at least 80% of oleic acid on the total of fatty acids, so as to obtain a 0.5 : 10 ratio between said turmeric powder and said high oleic sunflower oil;

Subjecting said turmeric powder and said high oleic sunflower oil to stirring, so as to obtain a mixture comprising said turmeric powder and said high oleic sunflower oil;

Filtering said mixture, so as to remove said turmeric powder and obtain said turmeric -based oil solution.

2. Method according to claim 1, comprising using a turmeric powder in which said total amount of curcuminoids active principles is at least 2%.

3. Method according to claim 1, or 2, wherein said turmeric -based oil solution, obtained through said filtering, contains a total amount of curcuminoids active principles of at least 500 ppm.

4. Method according to any one of claims 1 to 3, wherein said turmeric -based oil solution, obtained through said filtering, is provided with a resistance to the forced oxidation that is at least 10% higher compared to the resistance to the forced oxidation of a high oleic sunflower oil as sampled, said resistance to the forced oxidation being measured in hours and determined through evaluation of the oxidative stability index (OSI) at H0°C.

5. Method according to any one of claims 1 to 4, wherein said subjecting said turmeric powder and said high oleic sunflower oil to stirring is carried out for at least 24 hours.

6. Method according to any one of claims 1 to 5, wherein said subjecting said turmeric powder and said high oleic sunflower oil to stirring is carried out at a temperature comprised between 40°C and 60°C.

7. Method according to any one of claims 1 to 6, wherein said subjecting said turmeric powder and said high oleic sunflower oil to stirring is carried out in presence of a flow of inert gas.

8. Method according to claim 7, wherein said inert gas comprises nitrogen.

9. Method according to any one of claims 1 to 8, wherein said filtering comprises using an alluviation filter.

10. Turmeric-based oil solution for food use, comprising a high oleic sunflower oil, said high oleic sunflower oil containing at least 80% of oleic acid on the total of fatty acids, and a predetermined total amount of curcuminoids active principles.

11. Turmeric-based oil solution according to claim 10, wherein said predetermined total amount of curcuminoids active principles is of at least 500 ppm.

12. Turmeric-based oil solution according to claim 10, or 11, said solution being provided with a resistance to the forced oxidation that is at least 10% higher compared to the resistance to the forced oxidation of a high oleic sunflower oil as sampled, said resistance to the forced oxidation being measured in hours and determined through evaluation of the oxidative stability index (OSI) at H0°C.