JPH0413990B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) Fruit juice is largely consumed in its raw state for beverages, but there is a demand for fruit juice that does not become cloudy and remains clear when mixed and prepared as a component of beverages. , has been increasing recently. The present invention provides a method for producing clarified fruit juice having the above characteristics from raw fruit juice. Target fruit juices include almost all fruit juices such as citrus fruits (Wenzhou, Hassaku, etc.), berries (strawberries), plums (plums, peaches, etc.), apples, grapes, pineapple, etc. (Prior Art) A method has been put into practical use in which suspended pulp is removed by centrifugation or ultracentrifugation, and then dissolved pectin is decomposed using an enzyme such as pectinase. However, as the enzymatic reaction is carried out at a high temperature of 40 to 60 degrees Celsius over several hours, it loses its aroma and adds a unique odor, making it impossible to avoid quality deterioration of the fruit juice.Furthermore, the enzymes used are expensive. However, it has the disadvantage that the cost of clarification increases. As a method to overcome these drawbacks, a method is being tested in which pectin is separately removed at room temperature using an ultrafiltration membrane. (Problems to be Solved) A problem with the method of treating fruit juice with an ultrafiltration membrane is that the membrane permeation rate rapidly decreases over time. For this reason, a large-scale membrane device is required to process a predetermined amount of fruit juice in a predetermined time, and this drawback may not provide enough advantages to replace the enzymatic method. The present invention devises a simple and inexpensive membrane permeation rate recovery method in the process of membrane processing of fruit juice by cross-flow, and by periodically applying this method, the average membrane permeation rate can be maintained high and the membrane device can be scaled up. It attempts to overcome the shortcomings of Washing with surfactants, acids, alkalis, oxidizing agents, enzymes, hot water, etc. is well known as a method for restoring the reduced membrane permeation rate, and is very effective if properly selected. However, this method can only be carried out after the operation has been completed and the liquid has been recovered. Membrane permeation rate recovery methods that can be performed during operation include reversing the flow direction of the stock solution, flashing at high speed to remove the fouling layer, creating an air-liquid interface by blowing air bubbles into the stock solution, and using a sponge added to the stock solution. There are methods such as scraping with a solid object such as a ball, and reverse permeation of the permeated liquid to remove the fouling layer on the surface of the membrane. However, the method of adding air bubbles or solids is only possible with tubular membrane modules, and cannot be applied to hollow fiber membrane modules or spiral or pleated membrane modules, which have good space and energy efficiency. Although the method of allowing a portion of the permeate to pass back through is effective, it has the disadvantage of returning the liquid that has permeated the cornea back to the original solution, and the disadvantage that it requires a pump to pressurize the permeate for reverse permeation. The simplest method is to reverse the flow direction of the stock solution or release the applied pressure to flash at high speed, but it is less effective. (Means for Solving the Problems) As a result of intensive research, the present inventors have considered a simple and effective method for restoring membrane permeation rate. That is, after closing the permeate outlet for a certain period of time to stop membrane permeation, the back pressure regulating valve is opened while the permeate outlet is kept closed to flush the stock solution. This is an operation that reverses the flow direction of the
This membrane permeation rate recovery method is characterized by continuing for 20 seconds or more, preferably 1 minute or more. (Effects of the Present Invention) According to the method of the present invention, the membrane surface contaminated by fruit juice treatment can be cleaned by a simple operation, and the membrane permeation rate is restored. By carrying out this process periodically, the average membrane permeation rate can be maintained high for a long period of time, thereby reducing the capital investment required to increase the scale of the membrane device in advance of anticipating fouling of the membrane surface. (Example) The following will explain based on an example. Comparative example 1 Satsuma mandarin straight fruit juice (sugar content Brix
10.7°) 50 through a cloth with a gap of 0.2mm x 0.2mm, and then use the device shown in Fig.
Clear fruit juice was produced by supplying the juice to a hollow fiber UF membrane module under conditions of m ³ /h and module outlet pressure of 1 Kg/cm ² . The module is an internal pressure type manufactured by Daicel Chemical, effective membrane area 0.44 m ² , hollow fiber inner diameter 0.8 mm, hollow fiber effective length 270 mm, membrane material polyether sulfone, pure water permeation rate 5/m ² , min・Kg/cm ² or more, trypsin inhibitor (molecular weight 28,000) elimination rate is 65-85%, ovalbumin (molecular weight 45,000) elimination rate is 99% or more. As shown in FIG. 2, the membrane permeation rate (=clarified juice production rate) decreased rapidly over time. Therefore, an operation was performed to reverse the flow direction of the stock solution in the module every 20 minutes, but no effect was observed in preventing or reducing the decrease in permeation rate over time. Reference Example 1 A clarified fruit juice was produced using the same juice, the same module, and the same conditions as in Comparative Example 1. However, instead of reversing the flow direction of the stock solution every 20 minutes, the permeate outlet was closed for 2 minutes every 30 minutes. In addition, the flow direction of the stock solution during the operation of closing the permeate outlet was alternately maintained as it was and reversed.
The results are shown in Figure 3. Close the permeate outlet and
The operation of flowing the stock solution has a great effect in restoring the reduced membrane permeation rate, and it is even more effective to reverse the flow direction of the stock solution at that time. The permeation rate recovery effect of this operation is shown in Table 1 as a recovery rate defined by the following equation. Rn＝Pn−P′n _-1 /Pn _-1 −P′n _-1 ×100 Rn: Permeation speed recovery rate (%) Pn: Permeation speed immediately after operation P′n _-1 : Immediately before Pn _-1 : Immediately after the previous operation

[Table] Reference example 2 Satsuma mandarin orange concentrate juice (sugar content Brix
11.1°) 30 was roughly filtered through a cloth with a gap of 0.2 mm x 0.2 mm, and then a membrane permeation experiment was conducted under the same conditions using the apparatus of Comparative Example 1. However, the permeate was also returned to the tank except for a small amount of sampling, so that the concentration of the stock solution was kept constant. FIG. 4 shows the influence of these changes on the recovery effect by varying the interval at which the permeate outlet is closed and at the same time reversing the flow direction of the stock solution and the time during which it is closed. The effects of each operation are expressed in terms of permeation rate recovery rate and are shown in Table 2. When the operation was performed at 10-minute intervals, a remarkable recovery effect was observed when the operation time was 20 seconds or more, and approximately 100% recovery was observed when the operation time was 1 minute or more. Also,
By comparing operations B, D, and F in Table 1, it is shown that the effect decreases when the operation interval becomes 40 minutes or more.

[Table] *The amount that should have been recovered by the previous recovery operation, but could not be recovered due to the short operation time, was also recovered, so it became larger. So, if you calculate it for the operation before the previous one, it will be 100%. Reference example 3 Lemon concentrated and reduced juice (sugar content Brix 6.0°) 15
was supplied to a hollow fiber UF membrane module using the same small flow line device used in Comparative Example 1 under conditions of a pump discharge rate of 0.6 m ³ /h and a module outlet pressure of 1.6 Kg/cm ² to produce clarified fruit juice. . The module has half the number of hollow fibers as that used in Comparative Example 1,
The same membrane was used except that the effective membrane area was 1/2. The operation continued for 2 hours while closing the outlet for the permeate (=clarified fruit juice) for 1 minute every 15 minutes and reversing the flow direction of the stock solution. As shown in Figure 5, the permeation rate recovery rate for each operation was 57%, 80%, 86%, 100%, 75%, 80%, 63
%, 50%, with an average of 74%. Reference example 4 Pineapple concentrated reduced fruit juice (sugar content Brix
11.3°) 20 was passed through a cloth with a gap of 0.2 mm x 0.2 mm, and then clarified fruit juice was produced using the apparatus used in Reference Example 3. The operation continued for 2 and a half hours while closing the permeate outlet for 1 minute every 15 minutes. As shown in Figure 6, the permeation rate recovery rate for each operation is 85%, 92%, 108%, 93%, 100%, 80%.
%, 77%, 100%, 83%, 92%, and the average recovery rate is
It was 91%. Reference example 5 Thierry concentrated fruit juice (sugar content Brix 6.7°)
20 Clarification treatment was carried out for 1.5 hours using the apparatus of Reference Example 3 under the same conditions. However, the membrane permeation rate recovery operation was performed alternately every 15 minutes and every 20 minutes. As seen in Figure 7 and Table 3, the recovery rate every 15 minutes is
55%, 72%, 71%, and recovery rate every 20 minutes is 54
%, 77%, and both showed similar effectiveness. Next, using the same fruit juice 20, clarification treatment was performed under exactly the same conditions except that the membrane permeation rate recovery operation was performed every 45 minutes. As shown in Figure 8, the recovery rates were 38% and 49%, with an average of 44%, which was two-thirds of the average recovery rate of 66% for every 15 minutes and every 20 minutes.

[Table] Example 1 Summer mandarin orange straight fruit juice (Sugar content Brix
10.1°) 50 using the same equipment as Comparative Example 1, pump discharge amount 1.2 m ³ /h, module outlet pressure 1.6
Clarification treatment was carried out under the condition of Kg/cm ² . As a membrane permeation rate recovery operation, the operation of closing the permeate outlet for 1 minute every 20 minutes was performed five times (from A to E in Figure 9) until 1 hour and 40 minutes after the start of operation. After closing the liquid outlet, the operation of opening the pressure regulating valve of the module outlet piping was performed four times (from F to R in FIG. 9). As shown in Table 4, the average recovery rate is 48% when the permeate outlet is simply closed, whereas the average recovery rate is 75% when the pressure applied to the supplied juice is released.
%, a 56% increase in recovery effect was seen.

【table】 [Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an apparatus for carrying out the method of clarifying fruit juice of the present invention, in which 1 is a stock juice tank;
2 is a supply pump, 3 is a regulating valve, 4 is a flow meter,
5 is a four-way valve, 6 is a hollow fiber UF membrane module, 7 is a regulating valve, 8 is a flow meter, 9 is a pressure gauge, 10 is a pressure gauge, and 11 is a permeate outlet. Figure 2 is Comparative Example 1, Figure 3 is Reference Example 1, Figure 4 is Reference Example 2, Figure 5 is Reference Example 3, Figure 6 is Reference Example 4, Figure 7 is the first half of Reference Example 5, Figure 8 is reference example 5
The latter half of FIG. 9 is a diagram showing the experimental results of Example 1.

Claims (1)

[Claims] 1. In a method for clarifying fruit juice using a cross-flow membrane method, after a membrane permeate outlet is closed for a certain period of time, the applied pressure is released while the membrane is in the closed state to prevent fouling on the membrane surface. The average membrane permeation rate can be increased by performing an operation for recovering the membrane permeation rate that has been reduced by removing the supplied fruit juice by flowing it at intervals of no more than 30 minutes for at least 20 seconds, preferably for at least 1 minute. A method for clarifying fruit juice, characterized in that: 2. The method for clarifying fruit juice according to claim 1, wherein the direction of flow of the supplied fruit juice is reversed.