WO2004071213A1

WO2004071213A1 - Method of removing unwanted components from an aqueous flow derived from the processing of edible products having a natural origin

Info

Publication number: WO2004071213A1
Application number: PCT/NL2003/000107
Authority: WO
Inventors: Bernhard George Van Bommel; Esther Hendrika Gerarda Peeters
Original assignee: Cargill Inc.
Priority date: 2003-02-13
Filing date: 2003-02-13
Publication date: 2004-08-26
Also published as: AU2003207427A1

Abstract

In a method for the removal of unwanted components from an aqueous flow derived form the processing of edible products having a natural origin a treating agent comprising at least one fatty acid or acylglycerol derivative thereof is added to the aqueous flow in an amount sufficient to transfer the components aimed for from the aqueous flow to the treating agent. Thereafter the aqueous flow is separated from the treating agent now comprising the components.

Description

METHOD OF REMOVING UNWANTED COMPONENTS FROM AN AQUEOUS FLOW DERIVED FROM THE PROCESSING OF EDIBLE PRODUCTS HAVING A NATURAL ORIGIN

FIELD OF THE INVENTION

The present invention relates to a method of removing unwanted components from an aqueous flow derived from the processing of edible products having a natural origin. In particular, the invention is directed to the separation of compounds like lysophospholipids from an aqueous process stream in the processing of cereals, fruits, seeds, tubers, nuts, berries and the like, e.g. from a starch containing slurry in the preparation of glucose by conversion of grains like wheat and corn.

BACKGROUND OF THE INVENTION

It is known in the art of processing wheat to glucose syrup to filter the starch slurry (also termed "hydrolysate") in order to remove unwanted matter after an acid or enzymatic conversion step. Filtration using e.g. rotary vacuum precoat filters, membrane filters or pressure filters, but also flotation and centrifiguation can be used for this purpose. A rotary vacuum filter comprises a perforated drum with a cloth, which drum is rotably mounted upon a longitudinal axis. The outer circumference of the drum is covered with a precoat like perlite or diatomaceous earth, having an initial layer thickness of about 10cm. The fluid flow of starch hydrolysate is applied to the outside of the drum and sucked into the interior through the perforations by vacuum. Foreign matter and other unwanted compounds contained in the process flow like lysophospholipids, fats, proteins and so-called suspended solids, are removed by the precoat and in this way eliminated from the process flow. Because the top layer of the precoat such as diatomaceous earth primarily retains the unwanted compounds, this filter becomes blinded off. As a result, the filtering capacity thereof decreases in time. In order to maintain a constant filtering capacity the top layer is scraped by a knife or other suitable device, either continuously either intermittently, until the layer thickness gets too small and the layer needs to be replaced by a fresh one. The "contaminated" diatomaceous earth is discarded, e.g. by landfill or the like, or added to vegetable fibres for use in (cattle) feed. However, in addition to the expenses relating to this way of disposal, regulations become more strict. E.g. feed may not contain more than a limited amount of foreign material, dictated by national regulations. Furthermore the operational and maintenance costs of a rotary vacuum filter of this nature are high because of the energy requirements for the vacuum to be generated, the pollution encountered and the abrasive action of the precoat material to the equipment. In addition, due to the required replacement of the diatomaceous earth a full continuous operation cannot be achieved unless extra filter units are connected in parallel in the process line. Also a loss of glucose occurs which adversely affects the process efficiency. Therefor there is a general need to cost efficient techniques for the removal of unwanted matter from these types of flows, in particular to reduce the amount thereof to an acceptable level in the end product.

A further object of the invention is to reduce the overall amount of unwanted matter in a food processing flow such as a starch containing process flow, in particular to decrease the level of lysophospholipids .

Still another object of the invention is to reduce the level of fats, proteins and suspended solids as well. SUMMARY OF THE INVENTION

Accordingly the present invention provides a method of removing unwanted components from an aqueous flow derived from the processing of edible products having a natural origin, which method comprises the steps of adding a treating agent comprising at least one compound selected from the group comprising at least one fatty acid or a acylglycerol derivative thereof, to the aqueous flow in an amount sufficient to transfer the unwanted components from the aqueous flow to the treating agent, and separating the aqueous flow from the treating agent comprising the unwanted components. The method according to the invention comprises the treatment of an aqueous flow. This aqueous flow is derived from the processing of edible starting materials having a natural origin into products for consumption by humans or animals, i.e. food products and feed products . These starting materials having a natural origin comprise agricultural and horticultural products, and fruits. Examples comprise vegetables e.g. spinach and cabbage, grains including cereals and seeds e.g. wheat, corn, barley and sorghum, tubers like potatoes and sugar beets, fruits e.g. oranges, apples and berries, and others, e.g. sugar cane, chichorei, casave. In the present method this aqueous flow is treated with a medium essentially containing at least one fatty acid or an acylglycerol derivative thereof, preferably oils in view of water insolubility and density difference. The two streams are contacted in order to transfer the unwanted compounds from the aqueous phase to the treating agent. Low shear forces may be applied. Then the mixture is separated in its two phases, e.g. by allowing to stand for a sufficient amount of time. Subsequently the two phases thus separated can be isolated or treated otherwise. The unwanted components to be removed comprise compounds, the presence of which is undesirable in the products to be obtained from the aqueous flow concerned or which compounds interfere with the processing itself of the aqueous flow. As already stated, the aqueous flow is derived from the processing of edible starting materials having a natural origin. The treatment method according to the invention is carried out during this processing. The aqueous flow resulting from the treatment according to the invention is the main flow comprising the (intermediate) products for consumption. The flow comprising the treating agent and unwanted matter that has been removed, is considered as a by stream. However, the unwanted components do not comprise only contaminants or impurities to be discarded. The compounds themselves may be valuable e.g. from nutritional point of view. The unwanted components to be removed are selected dependent on the nature of the aqueous flow. Advantageously the components are selected from the group comprising lysophospholipids, phospholipids, fats, proteins, pesticides, organoleptic compounds, mycotoxines, tannins, suspended solids, pentosanes, enzymes and heavy metal complexes. Organoleptic compounds comprise flavours, aromas, colourants and odour compounds. In the processing of an aqueous flow derived from the processing of cereals, in particular a slurry comprising carbohydrates e.g. a (wheat) starch hydrolysate, the unwanted compounds comprise lysophospholipids, phospholipids, fats, proteins and suspended solids. In a particular embodiment the unwanted components have an oleophilic nature or proteinaceous nature. In a further preferred embodiment the unwanted components have an amphipatic nature. I.e. they have both polar and non-polar ends, and in addition are big enough for each end to display its own solubility behaviour. The polar end is water-soluble (hydrophilic) and the non-polar end is water-insoluble (lypophilic) . Without being bound to any theoretical concept it is believed that in the processing of wheat initially compounds having an amphipatic nature, specifically lysophospholipids (hereinafter abbreviated to LPL's), are incorporated in inclusion complexes. During conversion of starch into glucose these complexes fall apart and the LPL's are released. In the aqueous flow the LPL's thus released form micelles because the critical micelle concentration is exceeded. By the addition of a treating agent according to the invention these micelles are disturbed and fall apart into individual particles and molecules. These individual particles and molecules are readily transferred to the treating agent due to their (partial) lypophilic nature. As a beneficial side effect it has been shown that if any unsoluble proteins are present in the aqueous food processing flow, for the greater part they form a complex together with the components to be removed in particular LPL's, and oil, and consequently they are simultaneously removed. Here it should be noted that in the processing of wheat, the wheat oil (predominantly contained in the germs) themselves have been removed in a stage prior to the conversion of starch into glucose, because the presence of this oil would otherwise affect the quality of the end product. However, as explained hereinabove during removal of wheat lipids the unwanted compounds are still incorporated in inclusion complexes and cannot be extracted simultaneously with the wheat oil.

Hereinabove the principles of the invention have been explained in view of the processing of starch slurries. However the method according to the invention can be used in other technologies as well, e.g. in the production of beverages such as alcoholic beverages like beer and wine where the presence of LPL's is likewise undesirable, and fruit juices such as apple juice. During production compounds which are responsible of haziness can be removed by the method according to the invention. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an embodiment of a device for carrying out the method according to the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

The fatty acid or the fatty acid(s) of the acylglycerol of the treating agent has preferably a chain length of 14 to 20 carbon atoms, preferably 16 to 18 carbon atoms. The length of the non- polar chain influences the separation amongst others. The acylglycerol may be a mono-, di- or triacylglycerol. In view of rancidity saturated hydrogenated compounds are preferred. Advantageously the at least one fatty acid is selected such that the chain length thereof is essentially similar to the chain length of the compounds to be removed. Preferably the treating agent is of food grade quality. In particular the treating agent comprises an oil of natural origin, such as a vegetable oil or animal oil. Suitable examples of a vegetable oil include sunflower oil, palm oil, palm kernel oil, coconut oil, rapeseed oil and soy oil. Fish oil is an example of a suitable animal oil. Sunflower oil having a high oleic content, and palm oil because of efficiency are more preferred. In addition to the removal of LPL's the treatment according to the invention will preferably also reduce the content of other components such as fats, insoluble proteins and suspended solids in the aqueous flow. It is believed that suspended solids and in particular the insoluble proteins are partially entrained by the oil phase during phase separation, and are partially complexed by the oil. The simultaneous reduction of the fat and protein level is advantageous because otherwise these impurities are to be removed in an additional step. Processing aids in order to enhance the polar and/or hydrophobic interactions can also be used, whether they are present originally in the oil or added thereto on purpose. Processing aids may also be used with a view to increasing the effect of the density difference between the aqueous phase and oil phase.

Subjecting the food-processing flow to centrifugal forces is an advantageous way of physical assisting the phase separation. The method according to the invention is preferably performed on an aqueous flow comprising carbohydrates or derivatives thereof. A hydrolysate, which is obtained by acid or enzymatic conversion of e.g. corn or wheat, is a preferred process flow to be treated. The pH of the aqueous food processing flow may vary broadly. E.g. the method according to the present invention can be performed in the pH range from 2 to 8. Commonly known acids and alkaline compounds can be used to adjust the pH value. At the higher level (pH > 5.5) saponification may occur, therefor advantageously the pH is in the range from 3 to 5.5.

In order to accelerate the separation step of the process according to the invention the temperature may be raised, e.g. up to 100°C, preferably in the range of 70-90, e.g. 80°C provided that the quality of the aqueous flow and the end product to be attained therefrom are not deteriorated. At the higher temperatures the viscosity is reduced resulting in a faster separation between the aqueous phase and the phase of the treating agent.

Preferably the treating agent and aqueous flow are contacted intimately in order to increase the interaction between the different phases and thus the transfer of unwanted components from the aqueous phase to the treating agent. However, formation of a stable emulsion should be prevented. Conventional mixing will do, e.g. a common propeller mixer, spraying the aqueous phase into a bath of oil or vice versa, purging gas and the like. Low shear mixing is preferred in batch wise operation. Contact time and separation time can easily be determined by experimentation.

Oil tracers e.g. "Opacity Blue" can be used to determine an adequate separation. The amount of oil to be added depends on the amount and type of components to be removed. Based on conventional levels of components in wheat hydrolysate the volume ratio between oil and hydrolysate may vary within broad limits. In batch wise operation good results have been obtained in the range of 1:99 - 16:84, while the jlower ratios e.g. 2:98 show even better results.

The method according to the invention is preferably carried out under non-oxidizing conditions, more preferably in an inert atmosphere like carbon dioxide. The components to be removed by the method according to the invention have already been illustrated herein above. In a typical starch hydrolysate flow these components ( fats and proteins, except suspended solids) make up 2 wt.%, approximately 0.1-1% being LPL's. The aqueous food processing flow treated according to the invention could be further processed in a conventional manner, e.g. a starch slurry to a glucose syrup. The treating agent containing the unwanted components can be regenerated by removing these components. Then the treating agent is available for reuse, and allows a continuous process.

DETAILED DESCRIPTION of THE DRAWINGS

FIG. 1 shows diagrammatically a basic design of a device for carrying out the method according to the invention. This device comprises a holding tank 10. The tank 10 is provided with an inlet 12 connected to a supply line 14 for supplying an aqueous food processing flow into the tank 10. An upright baffle 16 connected to the bottom and side walls of the tank 10 provides an overflow for separation of the light oil phase from the relatively heavy water phase, and divides the tank into two compartments 18 and 20 respectively. Both compartments are provided with outlets, an outlet 22 provided in bottom 24 for discharging treated aqueous phase and an outlet 26 for discharging the oil phase. Oil is added to the tank 10 by a conduit 28, which is arranged in compartment 18, e.g. a perforated tube to which the oil is fed in a pressurized condition. The oil phase discharge outlet 26 may be connected to a further separation device 30, wherein the contaminants are separated from the oil. Then the purified oil can be returned to the conduit 28 by return line 32. Make up oil can be supplied via a line 34. The thus purified aqueous food processing flow leaving outlet 22 can be further processed in a conventional manner.

EXAMPLES

The invention will be further illustrated by way of the following non-limiting examples .

As starting material for each set of experiments a batch of glucose juice (DE = 37.5 - 42; pH about 4.5) was collected after acid conversion of wheat starch. This batch was divided into small portions and stored in a freezer, until needed. Table 1 and 2 summarize the conditions and results of the experiments. For each experiment performed under the conditions mentioned in Table 1 a portion was thawed during 8 hours at room temperature. Lysophospholipase (e.g. G-zyme G999, commercially available from Rhodia) was added in an amount of 0.02 ml/1 at the end of the 8- hour period and kept at 60°C overnight.

For those experiments without the addition of lysophospholipase, the samples were kept overnight at room temperature. On the day of the experiment the pH of the sample was adjusted using HC1 or NaOH to the required value. Optionally the sample was heated to the required temperature using a water bath. A quantity of oil was poured into a 3-way flask, and a quantity of the sample was added thereto. The total volume of oil and juice in each experiment was 1000 ml. The content was stirred using a propeller mixer. After the stirring had been stopped, the obtained mixture was poured into a separation funnel and allowed to stand for a certain period of time. After separation the two phases were collected separately. Analysis of the distribution of lysophospholipids (LPL), fat, protein, and suspended solids was performed.

Hereinafter the sample after the pH adjustment is referred to as sample A, the aqueous glucose phase after separation is called sample B, and the oil phase after separation is called sample C. Two sets of experiments were carried out. The conditions and results of the first set of five experiments numbered 1 to 5 using high oleic sunflower oil are shown in Table 1 and 2. This first set of experiments was done to get an indication of the process conditions.

Experiments 1 and 2 gave good results and experiments 3, 4 and 5 gave less good results.

In experiment 3 still all lysophospholipids (LPL's) are removed but the suspended solids, protein and fat content are much higher compared to experiments 1 and 2.

No lysophospholipase was added in experiments 2 and 4, but three parameters have been changed (amount of oil, temperature and pH) . Comparing the results of these experiments shows that a low amount of oil, low pH and high temperature improve the extraction of LPL, fat, protein and suspended solids. The results in Table 2 clearly indicate that LPL's initially contained in the glucose juice (sample A) have been removed completely and are found back in the oil phase (sample C) . The protein content is also reduced. This also applies to the fat content and insoluble matter (measure for suspended solids).

So a low amount of oil, low pH and high temperature are preferred to attain the positive effects of the method according to the invention.

Comparing experiment 5 with 1 three parameters have been varied (rpm mixer, separation time and pH) . Increase of the mixing speed, decrease of the separation time and high pH gave less good results, such as a smaller removal of the lysophospholipids and a lot of oil remaining in the aqueous glucose phase.

A second set of experiments was done to compare the effects of different types of oil to be used for the extraction. The conditions and results of the second set of experiments are summarized in Tables 1 and 2. Experiment 6, 7 and 8 gave good results and experiments 9, 10 and 11 gave less good results.

Sunflower oil high oleic seems the best oil type to use followed by palm oil. Rapeseed oil can also be used for the extraction of the LPL but the fat content of the glucose juice after the extraction compared to the experiments with the sunflower oil and palm oil is higher. pH and temperature are also important parameters that can vary dependent on the oil type used.

TABLE 1

Claims

C L A I M S

1. Method of removing unwanted components from an aqueous flow derived from the processing of edible products having a natural origin, wherein the method comprises the steps of adding a treating agent comprising at least one compound selected from the group comprising a fatty acid or an acylglycerol derivative thereof to the aqueous flow in an amount sufficient to transfer the unwanted components from the aqueous flow to the treating agent, and separating the aqueous flow thus treated from the treating agent comprising the unwanted components.

2. Method according to claim 1, wherein the fatty acid or acylglycerol derivative thereof has a chain length of 14 to 20 carbon atoms .

3. Method according to claim 2, wherein the fatty acid or acylglycerol derivative thereof has a chain length of 16 to 18 carbon atoms .

4. Method according to claim 1, wherein the fatty acid or acylglycerol derivative has a chain length similar to the chain length of the component to be removed.

5. Method according to claim 1, wherein the treating agent is an oil of natural origin.

6. Method according to claim 1, wherein the treating agent comprises sunflower oil and/or palm oil.

7. Method according to claim 6 , wherein the treating agent comprises a high oleic sunflower oil.

8. Method according to claim 1, wherein the unwanted components are selected from the group comprising lysophospholipids, phospholipids, fats, proteins, pesticides, organoleptic compounds, mycotoxines, tannins, suspended solids, pentosanes, enzymes and heavy metal complexes.

9. Method according to claim 8, wherein the unwanted components are selected from lysophospholipids, phospholipids, fats, proteins and suspended solids.

10. Method according to claim 1, wherein the unwanted components have an amphipathic nature.

11. Method according to claim 1, wherein the aqueous flow is a flow derived from vegetables, chosen from the group comprising cereals, grains, seeds, tubers, fruits, berries, nuts or mixtures thereof.

12. Method according to claim 1, wherein the aqueous flow comprises a flow of carbohydrates or derivatives thereof.

13. Method according to claim 1, wherein the pH of the aqueous flow is in the range of 2-8.

14. Method according to claim 13, wherein the pH of the aqueous food processing flow is in the range of 3-5.5.

15. Method according to claim 1, wherein the temperature of the aqueous food processing flow is in the range up to 100 °C.

16. Method according to claim 15, wherein the temperature of the aqueous food processing flow is in the range of 70-90°C.

17. Method according to claim 1, further comprising the step of adding an oil tracer to the aqueous flow to be treated.

18. Use of the method according to claim 1 in the preparation of glucose syrup.

19. Use of the method according to claim 1 in the preparation of beverages .