Food or edible material: processes – compositions – and products – Processes – Heating above ambient temperature
Reexamination Certificate
2000-11-16
2003-04-01
Weinstein, Steve (Department: 1761)
Food or edible material: processes, compositions, and products
Processes
Heating above ambient temperature
C426S399000, C426S413000, C426S634000, C426S518000
Reexamination Certificate
active
06541058
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for producing wet okara (“okara” is insoluble residue from “tofu”, or soymilk or soy protein production, and also known as soy pulp). More specifically, it relates to a process for producing wet okara by continuous sterilization.
2. Disclosure or the Prior Art
Okara has been used as a raw material of various food products and, in many cases, dried okara is predominantly used from the viewpoint of preservability. However, dried okara has a problem that it is inferior not only in water retention characteristics and reconstitution properties with water, but also in energy costs compared with those prior to drying.
On the other hand, although wet okara produced by heat sterilization with a batch-wise retort is marketed slightly, there are problems that the wet okara is hardly dispersed due to hardening with time and is liable to be colored, and its taste is spoiled. Further, although wet okara produced by a continuous production process is also known, since it is produced by application of electric current, it is difficult to elevate a temperature of wet okara by application of electric current unless salt is present. Then, when salt concentration is increased, the taste of wet okara is spoiled.
OBJECTS OF THE INVENTION
An object of the present invention is to provide a process for producing wet okara by continuous sterilization.
Another object of the present invention is to provide a process for producing wet okara having good preservability without deterioration of water retention characteristics.
These objects and other objects as well as advantages of the present invention will become apparent to those skilled in the art from the following description.
SUMMARY OF THE INVENTION
First, the present inventors attempted to use a scraper type heat exchanger as an apparatus for continuous sterilization of conventional okara. However, this continuous sterilization was unsuccessful because the surface of inner wall of the heat exchanger and pumps used were clogged with okara, when conventional okara was used. Then, the present inventors have studied continuous sterilization of wet okara intensively. As a result, it has been found that okara can be sterilized continuously by a scraper type heat exchanger without the above clogging problem by using finely divided wet okara having a specific particle size. Thus, the present invention has been completed.
That is, according to the present invention, there is provided a process for producing wet okara which comprises finely dividing wet okara, feeding it into a scraper type heat exchanger, heating at a temperature of not lower than 120° C., cooling the heated product and filling and sealing the cooled product in a container or package aseptically. The wet okara of the present invention has good preservability.
In the present invention, preferably, the finely divided wet okara has a particle size of 10 to 100 &mgr;m (the particle size is determined by a coulter counter). Further, preferably, the wet okara has a water content of at least 70% (by weight, hereinafter all percents are by weight unless otherwise stated), and the scraper type heat exchanger has an indirect heating part equipped with at least one scraper blade and outer tubing, and is combined with a forced-feeding part, a holding part and a cooling part.
DETAILED DESCRIPTION OF THE INVENTION
The okara to be used in the present invention may be that derived from whole soybeans or defatted soybeans. The former okara is mainly obtained from “tofu” production and the latter okara is mainly obtained from production of isolated soybean protein using defatted soybeans which has been obtained from soybean oil production.
Suitably, the okara to be used in the present invention has a water content of 70% or more, normally 70 to 95%, preferably 75 to 90%, more preferably 80 to 90%.
When a water content of okara is too low, it is difficult to feed it into a scraper type heat exchanger with a pump at its forced-feeding part. Further, when the okara is eaten after passing through a scraper type heat exchanger, it has gritty mouthfeel, which spoils the taste thereof.
On the other hand, when a water content of okara is too high, okara dispersed in water is precipitated, which causes a watery taste, though a scraper type heat exchanger can be easily driven.
Suitably, the average particle size of okara in a wet state to be fed to a scraper type heat exchanger is 10 to 100 &mgr;m, preferably 10 to 50 &mgr;m, more preferably 20 to 40 &mgr;m. The particle size used herein is that determined by a coulter counter. However, since conventional okara cannot pass through a coulter counter, its average particle size was determined by sieve analysis in a wet state.
When okara has the fine particle size, fluidity is increased and okara can readily pass through a scraper type heat exchanger, thereby facilitating heat sterilization. On the other hand, when okara, such as commercially available one, has a larger particle size, okara is difficult to pass through a scraper type heat exchanger, which causes difficulties in continuous sterilization.
For example, conventional okara obtained from “tofu” production has an average particle size of, normally, about 200 to 1,000 &mgr;m. When okara having such a larger particle size is try to feed into a scraper type heat exchanger, okara adheres to the inner wall of a pump at its forced-feeding part, and/or the pump is clogged with so-called “navel of soybean” having a particle size of about 2 to 5 mm, which causes difficulties in constant feeding of okara into the scraper type heat exchanger. Even if a water content is 80% or higher, okara having such a larger particle size shows dry and loose appearance and has no such fluidity as that of the okara to be used in the present invention which has the same water content. Therefore, it is difficult to pressurize okara to feed it into a scraper type heat exchanger. Thus, a commercially available wet okara is sterilized by a batch-wise retort.
The scraper type heat exchanger to be used in the present invention is combined with a forced-feeding part (a) for feeding okara by pressurization.
For feeding okara by pressurization, a feed pump can be used. As the pump, Mono Pump™ can be used generally. However, when okara has considerably high viscosity, a force pump (e.g., screw pump) can be used before Mono Pump™ to stabilize a flow rate.
The scraper type heat exchanger to be used in the present invention has an indirect heating part (b) equipped with at least one scraper blade and outer tubing. The outer tubing is preferably jacketed twofold tubing. Okara is forced to feed into and passing through this outer tubing. Steam (high pressure steam: 2 to 5 kg/cm
2
, saturated vapor temperature: 120 to 170° C.) or water heated to an elevated temperature is passed through the jacket and the inner wall of the jacketed tubing is continuously scraped and renewed with sharp scraper blades (normally, 2 to 4 blades) attached to a rotor part to prevent scorching. Suitably, the scraper blades (the rotor, etc.) are allowed to revolve smoothly on the inner wall of the outer tubing in the indirect heating part to improve heat conduction of okara fed to the scraper type heat exchanger. Further, suitably, the clearance between the inner wall of the outer tubing and the blade (rotor) is 5 to 50 mm, preferably 10 to 30 mm, more preferably 15 to 25 mm to reduce pressure loss of okara fed in the scraper type heat exchanger.
Okara is sterilized by heating at a temperature of not lower than 120° C., preferably, 120 to 150° C.
The scraper type heat exchanger to be used in the present invention is combined with a holding part (c). Preferably, holding time is 2.6 to 26 minutes in case of sterilization at 120° C., 49 seconds to 8.1 minutes in case of sterilization at 125° C., 16 seconds to 2.6 minutes in case of sterilization at 130° C., 5 to 49 seconds in case of sterilization at 135° C., 1.5 to 15.5 seconds in case of sterilization at 140° C. and 0.5 to 5 seconds i
Ezaki Mitsuo
Inaba Mihoko
Kanada Yasuhumi
Mitsuyoshi Kurimoto
Yamaguchi Masayuki
Fuji Oil Company Limited
Weinstein Steve
Wenderoth , Lind & Ponack, L.L.P.
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