JP4929456B2 - Sterilizer for liquid food - Google Patents

Description

  The present invention relates to a sterilization apparatus for liquid food that continuously sterilizes a liquid food flowing in a thin layer in a flow path by irradiating with infrared rays.

  In many cases, heat sterilization of liquid foods such as milk and liquid seasonings is performed by a sterilizer that heats and sterilizes liquid foods using a plate heat exchanger or a tube heat exchanger.

  A sterilization apparatus using a plate-type heat exchanger passes water vapor and liquid food alternately through a gap between stainless steel plates and sterilizes them by exchanging heat. As for sterilization by this sterilizer, a low-viscosity food becomes a target food.

A sterilization apparatus using a tube-type heat exchanger passes superheated steam or steam to the outside of a tube and flows food in the heated tube to sterilize it indirectly. For sterilization using this sterilizer, both low-viscosity foods and high-viscosity foods are targeted foods.
JP 2000-93136 A Supervised by Toshimasa Yano, Basic Course on Food Engineering 10 "Food Reaction Engineering Chapter 3 Sterilization" Korin 1990

  In these sterilizers, since heat is transferred through a plate heat exchanger or a tube heat exchanger, the food comes into direct contact with the surface of the hot plate or tube, and the protein in the food on the plate or tube surface. Etc. are easily altered, and the alteration is likely to adhere and deposit as dirt on the plate or tube surface. Then, the attached and accumulated metabolite is peeled off during the flow of the food and mixed as a foreign substance in the food, which may deteriorate the quality of the food.

  In addition, when metamorphs adhere to and accumulate on the plate or tube surface, the heat exchange capacity of the plate or tube is reduced. In addition, when the sterilization apparatus is stopped, the bacteria propagate in the modified product (dirt), and the liquid food may be contaminated with the bacteria when the sterilization process is resumed. Therefore, these sterilizers need to be cleaned regularly.

  However, the structure of these sterilizers is complicated, and the amount of dirt that adheres is large, so that the cleaning operation is difficult and requires a considerable cleaning cost. In addition, a large amount of cleaning water is required to clean these sterilizers, and this cleaning water is expensive. In addition, since a large amount of washing water is discharged, a considerable cost is required for the waste water treatment of the washing water.

  The problems to be solved by the present invention are that, in a sterilization apparatus using a plate heat exchanger or a tube heat exchanger, a denatured product is easily generated during the sterilization treatment, and the denatured product (dirt) is washed. It is a difficult point.

  The main feature of the present invention is that the upper surface of the liquid food flowing through the flow path is directly heated with infrared rays in order to avoid the transformation due to overheating of the liquid food and the adhesion / deposition of the transformation product on the heat exchange surface. And

  Specifically, the present invention relates to a flow channel having an upper opening, a supply unit that supplies liquid food to an upstream side of the flow channel, and an infrared radiator that irradiates the liquid food flowing through the flow channel with infrared rays. And the flow path is inclined so as to become lower from the upstream side toward the downstream side.

  Here, the inclination angle α of the channel is preferably 1 to 5 degrees. This is because when the inclination angle α is within this range, the liquid food is well sterilized without producing an unsterilized portion. Moreover, it is preferable that the width direction cross section of the bottom face of the said flow path is linear. Further, the cross section of the bottom surface of the flow path may have irregularities.

  In this invention, the surface of the liquid food is directly heated by the infrared radiator, and the inner surface of the flow path is not directly heated by the infrared radiator, so the temperature of the inner surface of the flow path is lower than the temperature of the surface of the liquid food, At the boundary between the inner surface of the flow path and the liquid food, it is difficult for the modified product of the liquid food to be generated, and therefore, there is an effect that the contamination made of the modified product of the liquid food hardly adheres to and accumulates on the inner surface of the flow path.

  In addition, since the structure of the sterilization apparatus is simpler than that of the plate type sterilization apparatus or the tube type sterilization apparatus, the present invention has an effect that the sterilization apparatus can be manufactured at a low cost and can be provided at a low price.

  In addition, since the structure of the sterilization device is simpler than that of the plate type sterilization device or the tube type sterilization device, the present invention facilitates cleaning of the sterilization device, and thus can reduce the cleaning cost of the sterilization device. There is.

  In addition, since the present invention is such that a plate or tube at a high temperature does not come into direct contact with the liquid food, there is little generation of a denatured product of the liquid food, and the amount of dirt attached to the inner surface of the flow path is small. The cleaning water for cleaning the sterilizer can be reduced, and therefore the cost for obtaining the cleaning water can be reduced.

  In addition, since the present invention reduces the amount of cleaning water for cleaning the sterilizer as described above, the burden of processing the cleaning wastewater is reduced, and thus the cost for wastewater treatment can be reduced. is there.

  Further, according to the present invention, when the inclination angle α of the flow path is set to 1 to 5 degrees, the liquid food flows in a layered manner at a speed that is not so fast as to kill all the bacteria in the liquid food. Can be effectively sterilized without producing an unsterilized portion.

  Further, according to the present invention, when the cross section in the width direction of the bottom surface of the flow path is linear, the liquid food flows in a layered manner, the liquid food is uniformly irradiated with infrared rays in the width direction, and the liquid food is even in the width direction. The sterilization treatment is effected so that the unsterilized part does not flow to the downstream.

  Further, according to the present invention, when unevenness is provided in the longitudinal section of the bottom surface of the flow path, the liquid food is disturbed by the unevenness and the surface portion and the internal portion of the liquid food are well mixed, and the temperature of the internal portion is the sterilization temperature. And the inner part is well sterilized, and the unsterilized part does not flow downstream.

  In the sterilization of liquid food, the purpose of preventing the adhesion and accumulation of dirt caused by the metamorphic product generated by the thermal transformation of liquid food on the sterilization device is realized with a simple device configuration without causing a decrease in sterilization ability. did.

  1 is a side view of a liquid food sterilizer according to the present invention, and FIG. 2 is a cross-sectional view of the liquid food sterilizer of FIG.

  In these drawings, reference numeral 10 denotes a flow channel, and the upper side of the flow channel 10 is open and has a substantially U-shaped cross section. The channel 10 is inclined so as to become lower from the upstream side toward the downstream side. The channel 10 is supported from below by a support 12. The inclination angle α of the flow path 10 can be adjusted by an angle adjusting screw 14. In addition, temperature sensors (not shown) are attached to various parts of the flow path 10 so that the temperatures of the various parts of the flow path 10 can be measured.

  A supply section 16 for supplying liquid food to the flow path 10 is provided integrally with the flow path 10 on the upstream side of the flow path 10, and the liquid food overflowing from the supply section 16 continuously forms a thin layer in the flow path 10. It comes to be supplied. A food injection pipe 18 for injecting liquid food into the supply unit 16 is connected to a position below the supply unit 16.

  Above the channel 10, an infrared radiator 20 that irradiates the liquid food flowing in the channel 10 with infrared rays is provided substantially parallel to the channel 10 at a predetermined distance from the channel 10. The infrared radiator 20 is supported on the support base 12 via a support member 22. The infrared radiator 20 is connected to a power source (not shown).

  Here, the inclination angle α of the flow path 10 is preferably 1 to 5 degrees. When the inclination angle α is within this range, the liquid food flows in layers at a speed that is not too fast to kill all the bacteria in the liquid food, so that the liquid food can be sterilized well without causing unsterilized parts. can do

  Moreover, it is preferable that the width direction cross section of the bottom face of the flow path 10 is linear. When the cross-section in the width direction of the bottom surface of the flow path 10 is linear, the liquid food flows in layers, the liquid food is irradiated with infrared rays evenly in the width direction, and the liquid food is uniformly sterilized in the width direction. This is because the sterilized portion does not flow downstream.

  The cross section of the bottom surface of the channel 10 may be provided with irregularities. When unevenness is provided in the cross section of the bottom surface of the flow path, the liquid food is disturbed by the unevenness, the surface portion and the internal portion of the liquid food are well mixed, the temperature of the internal portion of the liquid food rises to the sterilization temperature, This is because the portion is well sterilized and the unsterilized portion does not flow downstream.

  Next, the case where liquid food is sterilized using this sterilizer will be described with reference to FIGS.

  The liquid food to be sterilized is injected into the supply unit 16 through the food injection pipe 18. The amount of liquid food injected is adjusted by a valve (not shown) and a flow meter (not shown) attached in front of the food injection pipe 18. The liquid food injected into the supply unit 16 overflows the upper part of the supply unit 16 and flows through the flow path 10 in a thin layer flow. The flow rate and thickness of the thin laminar flow at this time are controlled by adjusting the amount of liquid food injected into the supply unit 16 and the inclination angle α of the flow path 10.

  The liquid food is irradiated with infrared rays from the infrared radiator 20 while flowing through the flow path 10 and heated to a predetermined temperature. Since the final temperature of the liquid food is determined by the temperature of the infrared radiator 20, the distance between the infrared radiator 20 and the liquid food, the residence time and the thickness of the liquid food, it is necessary to appropriately determine these operating conditions.

  In this apparatus, the flow path 10 is made open in the aseptic area, and the flow path 10 is flowed in a uniform thin layer flow of 0.5 mm to 5 mm, and the liquid food is directly irradiated with infrared rays. The liquid food is sterilized so that it does not become hotter than necessary.

  When liquid food is sterilized continuously using infrared rays as a heat source, if the thickness of the fluid liquid is large, the heat transfer area with respect to the volume becomes small, and sufficient sterilization cannot be performed. Therefore, it is necessary to flow the liquid food in a thin laminar flow, but it is difficult to control the thickness when the liquid food is flowed on a horizontal plane. This device is devised so as to have an optimum thickness by providing an appropriate inclination to the flow path.

  The operating conditions for raising the liquid food to a predetermined temperature were examined. As the liquid food, a soy sauce-based seasoning liquid such as “Mentuyu” or “Natto sauce” was assumed, and the target temperature was set to 75 ° C.

  The results of measuring the thickness of the liquid film by changing the flow rate and the angle of the flow path are shown in Table 1. In this experiment, infrared rays were not irradiated. From the table, the thickness of the liquid film does not change much even if the flow rate is changed, but the angle of the flow path greatly affects the thickness of the liquid film, and the value is in the range of 0.4 mm to 5 mm. . Since the thickness of the liquid film greatly affects the staying time of the heating unit, the angle adjustment is an important factor in controlling the temperature of the liquid food.

  FIG. 3 shows the temperature rise when water is passed through the apparatus while irradiating infrared rays. In this experiment, the surface temperature of the infrared radiator is constant at about 650 ° C. The parameter in the figure was the angle of the flow path and was changed from 0 ° to 5 °.

  From the results shown in FIG. 3, it can be seen that the smaller the flow rate and the greater the angle, the greater the temperature rise. The larger the angle, that is, the higher the temperature rise as the liquid film is thinner, indicates that the temperature rise is larger when the flow is made faster with a thin liquid film than with a thick liquid film even at the same flow rate. This is a great merit of using a thin laminar flow.

  Assuming that the temperature of the liquid food is raised from room temperature to 75 ° C., it is necessary to raise the temperature by 55 ° C., and it can be seen from FIG. 3 that this apparatus can be sufficiently achieved.

  Using this sterilizer, it was examined whether actual bacteria can be sterilized. Since a soy sauce-based seasoning liquid is assumed, salt-tolerant lactic acid bacteria and salt-tolerant yeast are the target bacteria for sterilization. Here, salt-resistant lactic acid bacteria (Tetragenococcus halophillas) were used.

  The results of measuring the number of bacteria when not irradiating with infrared rays are shown in Table 2, and the measurement conditions are shown in Table 3. In Table 2, 0 sec represents that the collected sample immediately after the outlet was immediately cooled and the number of bacteria was measured, and 30 sec represents that the temperature was maintained for 30 seconds after the sample was collected. From this result, the number of bacteria is 0 at the outlet, and in this case, it can be seen that sterilization is sufficiently possible under these conditions without being held at a high temperature.

Lactic acid bacteria are suspended in a 3% saline solution at a concentration of 10 ⁶ CFU / ml, this saline solution is flowed through the flow path, and this saline solution is irradiated with infrared rays from an infrared radiator to heat the saline solution before heating ( The number of viable bacteria in the saline solution at the inlet) and after heating (outlet) was measured. At this time, the flow rate of the saline was 240 ml / min, the inclination angle α of the flow path was 1 degree, and the distance from the infrared radiator to the saline was 50 mm.

  As a result, the saline inlet temperature was 29.8 ° C. and the outlet temperature was 87.6 ° C., and no viable bacteria were detected in the saline at the outlet.

  In the apparatus of the present invention, temperature sensors are attached to a plurality of parts of the flow path, that is, the parts shown in (1) to (6) of FIG. 4, the distance from the infrared radiator to the saline solution is 60 mm, and other conditions In the same manner as in Example 3, the temperature at each part of the flow path and the number of viable bacteria in the saline solution at that part were examined.

  The temperature and the number of viable bacteria in each part of the channel were as shown in Table 4 and FIG. From this result, it can be seen that all viable bacteria have been killed at the site (4) 360 mm downstream from the heating start position, and that the temperature at the site (4) is 71.8 ° C.

  Considering that there is a limit to the installation area of the sterilizer, it is difficult to increase the area of the flow path, and it is not suitable for applications to sterilize liquids to be processed such as milk that need to be processed in large quantities. It is effective for the purpose of sterilizing a liquid to be processed, such as a seasoning liquid, which is sufficient if a small amount is sterilized.

It is a side view of the sterilizer for liquid foods concerning this invention. It is sectional drawing of the sterilizer for liquid foods concerning this invention. It is a graph which shows the relationship between the flow volume of the liquid food which flows through a flow path, and the rising temperature of liquid food. It is explanatory drawing which shows the site | part which measured the temperature of the salt solution which flows through a flow path, and the number of viable bacteria. It is a graph which shows the temperature change of the salt solution which flows through a flow path, and the change of the survival rate of a living microbe.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Flow path 12 Support stand 14 Angle adjustment screw 16 Supply part 18 Food injection pipe 20 Infrared radiation body 22 Support member

Claims (5)

In the liquid food, the liquid food is directly irradiated with infrared light from above the liquid food that flows through the flow path, the supply section that supplies the liquid food to the upstream side of the flow path, and the liquid food that flows through the flow path. And an infrared radiator that directly heats the liquid food to a temperature at which the bacteria are killed, and the flow path is inclined so as to become lower from the upstream side toward the downstream side. Sterilization equipment.   The liquid food sterilizer according to claim 1, wherein the flow path has an inclination angle α of 1 to 5 degrees.   The liquid food sterilizer according to claim 1 or 2, wherein a cross section in the width direction of the bottom surface of the flow path is linear.   The liquid food sterilizer according to any one of claims 1 to 3, wherein a cross section of a bottom surface of the flow path has irregularities.   The sterilizer for liquid food according to any one of claims 1 to 4, wherein the thickness of the liquid food flowing on the flow path is 0.5 to 5 mm.

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