JPS6243477B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for preventing flavor deterioration during storage of refined soybean oil, particularly due to light. Refined soybean oil may initially be odorless, but if it is stored for a long time in contact with air, it develops various odors and reduces its commercial value. This phenomenon is particularly accelerated when soybean oil is exposed to light. For example, if refined soybean oil is sealed and stored in a can immediately after refining, the flavor will not deteriorate over a long period of time;
The flavor deteriorates considerably in 2 to 3 weeks when exposed to diffused light, and within 2 to 3 hours when exposed to direct sunlight. The odor that develops during storage of purified soybean oil is called a return odor, and among these, the odor of deterioration due to light is a hay-like odor, which is an unpleasant odor unique to soybean oil. Conventionally, linolenic acid, linoleic acid, phospholipids, unsaponifiable substances, oxidized polymers, etc. have been cited as causative substances for the development of returned odor, but no satisfactory preventive measures have been found yet. The present inventors investigated various ways to prevent the deterioration of flavor caused by light during the storage of refined soybean oil, and found that unsaponifiable substances remaining in refined soybean oil, mainly chlorophyll and related substances, were exposed to light. chlorophyll and its related substances can be completely removed in the soybean oil refining process to prevent the flavor deterioration of refined soybean oil caused by light. It is impossible to completely remove these related substances through normal decolorization processes, and a special process to remove unsaponifiables is required to reduce the unsaponifiables content in refined soybean oil to 0.1% by weight or less. They discovered the need and special features and completed the present invention. That is, in addition to the usual soybean oil refining process consisting of degumming, deacidification, decolorization, and deodorization processes, the present invention adsorbs unsaponifiables using activated carbon after the degumming process and before the deodorization process. This is a method for preventing flavor deterioration of refined soybean oil, characterized in that the content of unsaponifiables in refined soybean oil is reduced to 0.1% by weight or less by repeating the removal operation at least four times. The method widely practiced so far for refining soybean oil consists of a degumming step with water or an aqueous acid solution, neutralization of free fatty acids with an aqueous alkaline solution, and washing away of the resulting soap with warm water. These include an acid process, a decolorization process using an adsorbent such as activated clay or activated carbon, and a deodorization process using steam under reduced pressure. Although this refining step removes some of the non-glyceride impurities contained in soybean crude oil, some unsaponifiables such as tocopherols, sterols, pigments, etc. remain. The amount of unsaponifiables remaining in this refined soybean oil is usually around 1% by weight. Conventionally, tocopherols, which are unsaponifiable components, play an important role in maintaining the stability of fats and oils as natural antioxidants, so it has been considered desirable for them to remain. Since it is stable and inert, it is said that there is no problem unless it is in extremely large quantities, and therefore no special operation is carried out to remove these unsaponifiables. Therefore, trace amounts of pigment components such as chlorophyll and related substances that are included in these unsaponifiable components and passed through the decolorization step are thermally decomposed in the next deodorization step. The present inventors speculate that the thermal decomposition products of chlorophyll and its related substances play a role in triggering the appearance of haystack odor in refined soybean oil, and in order to completely remove this chlorophyll and its related substances, it is necessary to It was concluded that it is necessary to perform special operations to remove unsaponifiables during the purification process. The reason why activated carbon was used to adsorb and remove unsaponifiables in soybean oil in the method of the present invention is that activated carbon has a higher ability to absorb unsaponifiables than other adsorbents such as activated clay, acid clay, activated alumina, and clay. This is because the adsorption ability is even better. In addition, methods for adsorbing and removing unsaponifiables in soybean oil using activated carbon include adding activated carbon to soybean oil and stirring it, and then removing the waste activated carbon by filtration or centrifugation, and using a tower filled with activated carbon. There are methods such as allowing soybean oil to pass through. In the method of the present invention, the treatment of soybean oil with activated carbon is carried out after the degumming step and before the deodorizing step, and is repeated at least four times to reduce the unsaponifiables content of the refined soybean oil to 0.1% by weight or less. However, if activated carbon treatment is performed before the degumming step, the activated carbon will adsorb gaseous substances, reducing its ability to adsorb unsaponifiables. In addition, if it is carried out after the deodorization process, there is a risk of imparting odor or deteriorating the flavor to refined soybean oil, and activated carbon treatment reduces the content of unsaponifiables in soybean oil to 0.1% by weight or less. It is necessary to repeat this process four or more times, and only by reducing the unsaponifiable content to 0.1% by weight or less can tocopherols, sterols, etc.
It is possible to almost completely remove trace components such as chlorophyll that coexist with other unsaponifiable substances, and it is also possible to prevent the deterioration of flavor of refined soybean oil due to light, that is, the development of hay smell. . According to the method of the present invention, it is possible to prevent the deterioration of the flavor of refined soybean oil due to light.
It is extremely effective in preventing the appearance of hay smell in soybean salad oil, etc. The method of the present invention mainly provides a method for preventing the deterioration of flavor of refined soybean oil due to light, but it also provides a method for preventing deterioration of the flavor of refined soybean oil due to light.
Adding about 1000 ppm can also prevent flavor deterioration due to autoxidation during storage of the soybean oil. Next, examples of the present invention will be shown. Example 1 100 ml of 80°C warm water was added to 5 kg of soybean crude oil obtained by extracting raw soybeans with n-hexane,
After stirring at around 85°C for 30 minutes, the mixture was centrifuged to obtain degummed oil. Add 5 ml of phosphoric acid to this degummed oil and stir at room temperature for 30 minutes, then add 25 ml of a 15% aqueous solution of caustic soda.
The mixture was added and stirred at room temperature for 45 minutes, and then the supernatant was filtered to obtain a deacidified oil. Add 30g of activated clay to 3kg of this deoxidized oil and heat at 100℃.
After stirring for 15 minutes, the bleached oil was obtained by filtration. 100 g of activated carbon was added to this decolorized oil, stirred at room temperature for 1 hour, and filtered to remove unsaponifiables, which was repeated 7 times. The resulting desaponified oil was heated to a temperature of 260°C.
Deodorization treatment was carried out by blowing steam into the solution for 1 hour at a temperature of about 6 mmHg under a reduced pressure of about 6 mmHg. The unsaponifiable content of the obtained refined soybean oil was determined to be 0.05% by weight according to the Standard Oil and Fat Analysis Test Method compiled by the Japan Oil Chemists' Association. Control Example 1 Refined soybean oil having an unsaponifiable matter content of 0.72% was obtained in the same manner as in Example 1, except that no unsaponifiable matter removal treatment using activated carbon was performed. In order to clarify the effects of the method of the present invention, 150 g of the refined soybean oil obtained in the above Examples and Control Examples were collected into wide-mouthed bottles each having a capacity of 250 ml.
Fluorescent light irradiation device (For details, see Oil Chemistry, Vol. 27, No. 8, August 20, 1978, Published by Japan Oil Chemists' Association, pp. 31-36, Effect of Citric Acid on
the Oxidative and Flavor Stability of Soybean
A flavor deterioration acceleration test was conducted using 7,000 lux fluorescent light irradiation for 8 hours, and the development of the dried grass odor was observed through a sensory test. The sensory test was conducted by 10 experienced people (5 men and women aged 20 to 50).
The evaluation was conducted using a 5-point scoring system by a panel of researchers. The results are shown in the table below.

[Table] Example 2 γ-
700 ppm of tocopherol was added and dissolved. A storage test was conducted in which 150 g of this refined soybean oil and the refined soybean oil obtained in Comparative Example 1 were each taken into wide-mouthed bottles with a capacity of 250 ml, sealed, and left on a table in a room away from direct sunlight for one month. At some point, the development of the deterioration odor was observed through a sensory test. The sensory test was conducted by 10 experienced people (5 men and women aged 20 to 50).
The evaluation was conducted using a five-point scoring system by a panel of researchers. The results are shown in the table below.

【table】

Claims (1)

[Scope of Claims] 1. In addition to the usual soybean oil refining process consisting of degumming, deacidification, decolorization, and deodorization processes, activated carbon is used to remove unsaponifiables after the degumming process and before the deodorization process. By repeating the adsorption and removal operation at least four times, the unsaponifiable content in refined soybean oil can be reduced.
A method for preventing flavor deterioration of refined soybean oil, characterized by reducing the flavor to 0.1% by weight or less. 2. The method according to claim 1, wherein tocopherols are added to the refined soybean oil obtained by the above method.