JPS6312575B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for removing bran odor and old rice odor from rice and producing rice with excellent flavor, color, stickiness, and texture.

More specifically, the present invention provides retort cooked rice food,
This invention relates to a method for processing rice suitable for use as a raw material for rice crackers, rice starch products, etc.

In recent years, too much rice has been harvested, and a large amount of surplus rice is being stored as old rice or old rice. Even with various storage methods, old rice and old rice gradually change in quality during storage, acquire a musty odor and an unpleasant sour taste, become sticky, lose luster, lose color, and become hard. It will increase and become dry. Therefore, even when rice is processed into cooked rice, rice cakes, rice crackers, etc., the older the rice gets, the less flavorful it becomes and the more it becomes unpalatable, making consumers increasingly shy away from it.

In general, the odor of old rice is caused by the further decomposition of fatty acids produced by lipid oxidation, resulting in carbonyl compounds,
This is thought to be due to an increase in aldehydes such as n-valeraldehyde and n-caproaldehyde. Also, as the rice becomes older, its stickiness decreases,
The increase in hardness is thought to be due to the hardening of cell membranes and tissues, which prevents water from penetrating, which delays the transition from the β-type starch to the α-type starch, resulting in insufficient gelatinization.

Consumers are particularly sensitive to musty smells.
For example, if retort-packed rice has this smell, it will be thrown away without even being eaten after just opening the package. This kind of rice bran odor is present not only in old rice, but also in new rice that is less than a year old, and depending on the storage method, the rice bran smell can be as strong as old rice. .

Conventionally, methods have been considered to remove such rice bran odor. For example, there are methods such as adding a flavor improver, washing with alcohol, etc., and enzymatic treatment. Lysine hydrochloride and dehydroxyacetone are used as flavor improvers. The purpose of using alcohol, etc. is to wash away the odor components of old rice. The enzyme treatment method is a method in which an enzyme agent consisting of lipase, amylase, protease, and cellulase is applied to decompose and dissolve fat, starch, protein, and cell membranes near the surface of rice grains to some extent. However, these methods are still complicated to operate and have problems in post-treatment of alcohol and enzymes, so they have not been put into practical use.

In order to find a method of cooking rice that reduces the disparities between varieties and regions of production and makes it even more delicious, the inventors of the present invention not only use old rice or rice that has lost its flavor due to poor storage conditions, but also new rice. First, I tried these various flavor improvement methods. However, although each method is effective to some extent, each has its own merits and demerits.Especially when it comes to cooked rice retort food, which is packed in a sealable container and sterilized by high-temperature cooking, the flavor may no longer resemble that of cooked rice. This method was not always satisfactory, as the rice grains were more likely to crumble or become brown, resulting in loss of luster.

Therefore, when considering improving the flavor of cooked rice, the present inventors focused on the following several facts. Conventionally, when cooking rice, it is said that it is better to wash the rice thoroughly with water to remove the adhering bran and other odor-absorbing components, and then soak the rice in water to absorb water. When compared, I found that the smell of bran and old rice was stronger when I used warm water. Even if the food had been washed and absorbed with cold water, the smell of rice bran and old rice was stronger when it was cooked in cold water and when it was cooked directly in boiling water. Enzymes that decompose lipids are mainly involved in the production of components known as bran odor and old rice odor. When cooked from water, the rice slowly passes through a temperature range of 30 to 40°C, where these enzymes are most active, but when cooked directly with boiling water, the rice quickly passes through this temperature range. Enzymes are immediately deactivated by heat when the temperature rises, so their activity can be minimized. Rice lipids exist in large quantities near the surface layer of the rice grain, which forms the bran, and are easily broken down into fatty acids, which are the precursors of the bran odor and old rice odor components, due to the effects of oxygen in the air and attached microorganisms. Old rice bran has a lot of free fatty acids. Water for washing or soaking
When the pH is set to the acidic side, many enzymes, such as lipolytic enzymes, move away from the optimum pH range and become less effective. In addition to these, processing with boiling water is less likely to cause starch to run out and starch granules to crumble during cooking. When the pH is on the alkaline side,
The starch granules break down easily, and the starch becomes cake-like, resulting in sticky cooked rice.However, on the acidic side, the rice grains are tightly packed and do not sag or crumble easily, and have a good stickiness and texture. Rice contains flavone-based pigments, and when it is on an alkaline side, it becomes yellow, but when it is on an acidic side, it is almost colorless, increasing the whiteness of the rice and improving its color. Also, if it is on the alkaline side, proteins and fats will be decomposed by the alkali, producing an unpleasant odor and spoiling the flavor.

As a result of integrating the above findings and conducting intensive research, we have completed the present invention.

The present invention is a method for treating rice in which rice is brought into instant contact with neutral to weakly acidic hot water or steam at 70°C or higher.

The first feature of the present invention is that rice is heat-treated by immersing or sprinkling it in boiling water or steam at 70° C. or higher for several seconds to deactivate the enzymes that produce bran odor and old rice odor components. In this case, if you use rice that has been washed, thoroughly absorbed, and drained, the heat treatment time can be further shortened.For example, soaking the rice in boiling water at 80°C for 3 seconds can suppress the enzyme activity and reduce the rice bran. It was possible to suppress the generation of odor and old rice odor. In such instantaneous rapid heating, only the surface of the rice grains is treated, and the internal temperature rises only slightly, and the gelatinization of starch hardly occurs, which is sufficient to make rice flour and rice flour. Ta. Afterwards,
Even when washed, soaked, and absorbed in water, the loss of starch and flavor components can be minimized, and the flavor and texture of rice and rice cakes are not impaired, but rather improved. Immediately washing and soaking in water after instantaneous rapid heating treatment makes it easier to remove odor and off-taste components such as bran, colored substances, bran odor, and old rice odor that remained even after washing in advance. At the same time, the off-flavor and off-taste components that are newly generated until the enzyme is deactivated by heating and ceases to work are also eluted and removed. A marked improvement in quality was observed regardless of the production area.

The second feature of the present invention is that the water quality of hot water or steam is made weakly acidic with a pH of 7 to 2. This slightly acidic treatment tightens the rice,
The whiteness increases, the surface of the rice becomes glossy, the texture improves, and the quality of the rice can be significantly improved.

In the present invention, rice is subjected to rapid heat treatment by instantaneously contacting it with neutral to slightly acidic boiling water or steam at 70°C or higher, and then, if necessary, is washed, soaked, absorbed, and drained to produce a rice bran odor and old rice odor. This is a method to remove rice and improve rice quality. The treated rice thus obtained was then used as a raw material and normally steamed.
Alternatively, processed rice foods such as retort food and dried instant food such as cooked rice and mochi, shiratamako and joshinko made by grinding raw rice to remove the starch, and rice crackers made by drying and puffing, etc. It is something that can be manufactured.

The rice that can be used in the present invention is both glutinous rice and non-glutinous rice, regardless of the degree of polishing of the rice, such as polished rice, half-cooked rice, germ rice, and brown rice. It may have a strong odor, and is not particularly limited.

These rice can be used as is or washed with water beforehand.
After soaking in water and draining, it has neutral to weak acidity70
Momentary contact with hot water or steam at temperatures above ℃. The hot water or steam used for the instantaneous rapid heat treatment should be neutral to weakly acidic with a pH of 7 or below and around 2, preferably adjusted to a pH using an organic acid or an organic acid salt, and a small amount of salt. However, if alkaline earth metals such as calcium and magnesium or iron ions are included, they may combine with phytins in rice and cause starch alpha-ization. Therefore, it is desirable to use soft water with a low content of these metal ions.

Boiling water or steam is adjusted with water or organic acid-added water, and the organic acids include citric acid, tartaric acid,
An organic acid such as acetic acid is preferable, and its concentration may be any suitable concentration within the range of PH7 to 2. Addition of acid has the effect of preventing the elution of starchy substances and preventing discoloration.

Unless the temperature of boiling water or steam is 70°C or higher, it is not possible to prevent the bran odor that will occur later. Boiling water is immersed or sprayed at a temperature in the range of 70°C to 100°C, but if the temperature is high, it will take only a short time. 70
At 80°C, it takes several seconds to be effective, but at 80°C, for example, only 3 seconds of treatment can produce an effect. Also, water vapor is over 70℃
Although it is possible to use high-pressure steam at 120°C, the process will be completed in 1 to 2 seconds. It is advantageous for continuous large-scale processing. Since the treatment time varies depending on the temperature, it must be changed appropriately depending on the temperature of the hot water or steam at that time. In either case, it goes without saying that the rice grains must be heated evenly so that the heat is evenly distributed to each grain.

Rice treated in this way will not develop a bran odor, no matter what kind of treatment it undergoes afterwards. If necessary, it can be used as a raw material for retort foods, rice crackers, starch for processing, etc. by washing with water, soaking in water, draining, drying, etc.

Examples of the present invention will be shown below.

Example 1 Polished rice and germ rice are non-glutinous rice of the same variety and origin and are polished one month after harvesting, so-called new rice, and after polishing, the rice is packed in paper bags and stored in a warehouse at 15 to 20°C for one year. The stored so-called old rice was processed.

First, each rice was washed in running water for 5 minutes, drained, and left for 30 minutes. Next, the rice grains were transferred to a mesh basket and soaked in boiling water at 80°C containing 0.3% tartaric acid for a few seconds, being careful not to cause uneven heating, to instantaneously heat the surface of the rice grains. The rice was taken out and immediately placed in water, washed again under running water for 5 minutes, and then soaked in water for 30 minutes. The water was drained, and the product was packed in a retort pouch made of flexible plastic film with an appropriate amount of water to achieve the desired moisture content and sealed. These were placed in a retort heating cooking machine in the usual manner and sterilized by heating (113°C, 35 minutes), followed by a cooling process in the retort to obtain white rice. As a control, each rice was subjected to the same conditions except that the step of instantaneous rapid heating treatment was omitted.

As a result of the sensory test, the instantaneous rapid heating treatment significantly improved the flavor of all types of rice, and new rice had no bran odor, and old rice had no old rice odor at all. In addition, the whiteness increased, the color became better, the food did not fall apart when cooked, the stickiness increased, and the texture was improved. However, in the control, the new rice had a weak but noticeable bran odor, and the old rice had an odor so strong that it almost lost appetite.

Example 2 In Example 1, plain water (city tap water) with no added water used in the instantaneous rapid heating treatment process
Instead, we conducted a white rice cooking test near neutrality.

As a result, by heat-treating each type of rice, the flavor, color, stickiness, and other textures were significantly improved.

Comparing with the results of Example 1 in weak acidity,
On the neutral side, the pleasant aroma of cooked rice was felt more, and the whiteness was slightly reduced, but no other obvious differences were noticed. Different people have different preferences between those treated with weak acidity and those treated with neutrality, and it was difficult to decide between the two.

Example 3 Using polished sticky rice, new rice and old rice,
Retort cooking according to Examples 1 and 2,
Manufactured sekihan. At this time, I added a small amount of half-boiled red beans along with the sticky rice.

In either case, the rice subjected to the instantaneous rapid heat treatment had a good flavor with no bran odor or old rice odor, and the reddish color of the red rice due to the color of the red bean increased in brightness. In particular, the rice grains became less sticky and sticky like rice cakes, and the rice became more sticky and had a better texture.

Example 4 Glutinous rice was subjected to instantaneous rapid heating treatment according to Examples 1 and 2, steamed in a steamer, and pounded to produce mochi.

The heat-treated mochi had a good flavor without the odor of bran or old rice, had an increased whiteness, was sticky, and had a firm texture.

Example 5 Glutinous rice or non-glutinous rice treated with instantaneous rapid heating according to Examples 1 and 2 was ground as raw rice without further cooking, exposed to water to remove starch, and dried through ventilation to produce shiratamako and glutinous rice. A fresh powder was obtained.

The heat-treated rice had no smell of bran or old rice, was pure white, and remained suitable as a raw material for processing. Moreover, the yield was hardly reduced. On the other hand, those that were not heat-treated retained a bran odor and an old rice odor, and could not be made into high-quality fresh flour.

Example 6 The glutinous rice and non-glutinous rice subjected to the instantaneous rapid heat treatment according to Examples 1 and 2 were milled and kneaded to make dough, which was then dried and roasted and puffed according to a conventional method to produce rice crackers, arare, and kakimochi. .

The heat-treated rice crackers had an increased aroma and a refined flavor, and had a good texture when chewed, resulting in high-quality rice crackers. The degree of puffiness of the dough did not decrease, but rather improved.

Claims (1)

[Claims] 1. Rice with old rice odor or bran odor may be washed as is or in advance by washing, soaking, and draining, and then exposed to neutral to slightly acidic boiling water or steam at 70°C or higher for within a few seconds to remove the grains. The surface is rapidly heated to inactivate the enzymes that produce bran odor and old rice odor, and if necessary, washing with water, immersion in water absorption, and draining are performed to completely remove the bran odor and old rice odor and prevent their regeneration. A rice processing method characterized by: