<p>&nbsp;Refining&nbsp; Do in Edible oil&nbsp;การกลั่นน้ำมันสำหรับบริโภค</p>

The methods of protecting the oil against auto-oxidation of the past have not been entirely satisfactory. Particularly, they have been less efficient, more expensive and less effective than is desirable.

 

The present invention provides an improved method of refining with prevents auto-oxidation of oil associated with refining and deodorization and thereafter. This method is especially useful with the method of continuous refining and deodorization disclosed in my co-pending patent application Ser. No. 540,037 filed Oct. 7, 1983. In order to provide a more complete understanding of the present invention and the art of edible oil refining in general, reference may be had to this co-pending application, the disclosure of which is incorporated herein by reference.

 

SUMMARY OF THE INVENTION

In view of the problems of auto-oxidation encountered in the past, it is an object of the present invention to provide an improved method for refining and deodorization of edible oil which more efficiently and effectively protects the oil from auto-oxidation. It is also an object of the present invention to provide such protection without adding additional oil processing steps and either without the addition of anti-oxidants, or with the addition of lower quantities of anti-oxidants.

 

It is a further object of the present invention to improve the continuous refining and deodorization processes of the type which include air-isolation and continuous steps of degumming by acid-water washing of the oil and/or bleaching of the oil by absorption on clays and subsequent filtration.

 

In accordance with these objects, the present invention provides an improved method of continuous refining and deodorization of edible oil of the type including air-isolation and continuous steps of degumming by acid-water washing of the oil. The improvement comprises deaerating the oil during the step of degumming by deaerating the acid-water mixture used in the process of degumming to less than one thousand parts per billion of dissolved oxygen so that, as the acid-water 

mixture removes phosphatides, it also removes oxygen from the oil due to oxygen in the oil being dissolved into the deaerated acid-water mixture and removed therewith. Thus, without adding any additional oil processing steps the oil is deaerated during degumming. This is especially desirable since the phosphatides removed during degumming are natural anti-oxidants. Thus, the present invention protects the oil by deaeration in the very process which removes the natural oil anti-oxidants.

 

In order to provide a better deaeration of oil it is preferable to deaerate the acid-water used in degumming to less than one hundred parts per billion of dissolved oxygen. Most preferably, the deaeration results in an acid-water mixture of less than fifty parts per billion of dissolved oxygen.

 

Following deaerating by degumming with a deaerated acid-water mixture, the present invention preferably includes a step of bleaching which protects the oil against oxidation which would otherwise occur in contacting the oil with clay having oxygen retained thereon. Protection of the deaerated oil is provided by purging oxygen from the bleaching clay with nitrogen and/or oxygen-scavenging gases prior to using the clay in the bleaching process. Other liquids and solids added subsequent to degumming should also be deaerated.

 

Although the present invention functions well to inhibit auto-oxidation without adding any special material to the oil, the addition of an oxygen scavenger, such as sodium sulfite eliminates any traces of oxygen. This oxygen scavenger should be added to the water used in degumming. The volume of sodium sulfite added can be gauged by the amount of sodium sulfite remaining in the water after the water is removed by the centrifuge used in degumming. Thus, no oxygen scavenger remains in the oil.

 

For a further understanding of the invention and for further objects, features and advantages, reference may now be had to the following description of preferred embodiments taken in conjunction with the accompanying drawings.

 

What is claimed is:

1. An improved method for refining and deodorization of edible oil of the type including air-isolated and continuous steps of degumming by acid-water washing of the oil; the improvement comprising the step of deaerating the oil during the step of degumming by deaerating the acid-water mixture used in the process of degumming to less than one thousand parts per billion of dissolved oxygen so that as the acid-water mixture removes phosphatides it also removes oxygen from the oil due to oxygen in the oil being dissolved in the deaerated acid-water mixture and removed therewith.

2. The improved method of claim 1 wherein said step of deaerating the oil comprises deaerating the acid-water mixture to less than one hundred parts per billion of dissolved oxygen.

3. The improved method of claim 2 wherein said step of deaerating the oil comprises deaerating the oil to less than fifty parts per billion of dissolved oxygen.

4. An improved method for continuous refining and deodorization of edible oil of the type including air-isolated and continuous steps of degumming by acid-water washing of the oil and bleaching by clay filtration of the oil followed by removal of fatty acids by vacuum distillation; the improvement comprising the steps of:deaerating the oil during the step of degumming by deaerating the acid-water mixture used in the process of degumming to less than one thousand parts per billion of dissolved oxygen so that as the acid-water mixture removes phosphatides it also removes oxygen from the oil due to oxygen in the oil being dissolved in the deaerated acid-water mixture and removed therewith; andprotecting the deaerated oil from said deaerating step during the step of bleaching by deaerating the clay used in the bleaching step.

5. The improved method of claim 4 wherein said protecting step comprises: nitrogen gas purging of oxygen from the clay followed by fluorene gas purging of oxygen from the clay.

6. The improved method of claim 4 wherein said vacuum distillation is isolated and scaled so that the oil being subjected to vacuum distillation does not contact water or oxygen thereby preventing oxidation and hydrolysis of the oil.

7. The improved method of claim 6 wherein said step of deaerating the oil comprises deaerating the acid-water mixture to less than one hundred parts per billion of dissolved oxygen.

8. The improved method of claim 7 wherein said step of deaerating the oil comprises deaerating the acid-water mixture to less than fifty parts per billion of dissolved oxygen.

9. The improved method of claim 4 which further comprises adding an oxygen scavenger to the water used during the step of degumming.

10. The improved method of claim 9 wherein the oxygen scavenger comprises sodium sulfite.

11. The improved method of claim 1 which further comprises adding an oxygen scavenger to the water used during the step of degumming.

12. The improved method of claim 11 wherein the oxygen scavenger comprises sodium sulfite.