Enzyme treatment*
An enzyme step not deployed in the desired end product is a cloudy or “natural” “-looking apple juice. Otherwise, after juice extraction, the raw apple juice must be treated with enzymes to remove suspended solid materials. If not removed, this colloidal material can clog filters, slowing production and can cause the juice to form a haze later on. Enzymes work by hydrolyzing soluble pectinaceous materials, hemicellulose and other polymers and colloids that increase juice viscosity, thereby leaving the juice more easily filtered. Many enzyme preparations are available both in liquid and powder forms. They are all subject to conditions that can influence enzyme performance, such as pH, temperature, enzyme concentration and length of reaction time. Considering these variables, it is recommended that test trials be conducted with specific enzymes under typical operating circumstances to determine the proper concentrations and conditions.
There is a hot and cold method for an enzyme treatment. In the hot method, the enzyme is mixed into juice at 54°C and held for 1 to 2 hours. In the cold treatment, the enzyme is mixed into the juice at room temperature, 20°C and held 6 to 8 hours. The enzyme activity can be monitored by adding five milliliters of juice to 15 ml of HCL-acidified ethyl alcohol and observing the mixture for 5 minutes for gel formation. No gel formation means that the depectinization has been completed.
Tannin and gelatin treatment*
For highly astringent apples, tannin removal is beneficial. Many of these tannins can be precipitated with the addition of gelatin. However, in order not to remove all tannins and, therefore, some of the flavor and color of the juice, it is often the practice first to add more tannins and then precipitate a certain amount with gelatin. A classic, older procedure of possible value with overly astringent juices is described (Walsh, 1934):
Solution 1. Dissolve 9.45 g of tannin (tannin acid) in 176 ml of 95 percent ethyl alcohol. Then add 704 ml of water and mix thoroughly. Solution 2. Dissolve 21.2 g of gelatin in 704 ml of water and add 176 ml of 95 percent ethyl alcohol.
Heat a portion of the water and add the gelatin slowly, stirring continuously. Then add the rest of the water and dissolve the gelatin by heating in a pan of hot water or double boiler and stirring. Add the alcohol and mix well.
These solutions should be kept in stoppered bottles and may be used as needed, the alcohol acting as a preservative in both cases. In some cases, the gelatin will gel when cold but can be liquefied when needed by putting the container in hot water.
Four clear glass quart bottles should then be filled to the neck with apple juice and numbered 1, 2, 3 and 4. Then add to each bottle the following amounts of Solution 1 (tannin) and Solution 2 (gelatin).
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Bottle No. 1
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Bottle No. 2
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Bottle No. 3
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Bottle No. 4
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| Solution 1. (ml) |
10
|
10
|
10
|
10
|
| Solution 2. (ml) |
5
|
10
|
15
|
20
|
Measure and add the solutions shown to each bottle, adding the tannin first in all cases and shaking well after adding each solution. Let the bottles stand for 10 minutes. The bottle showing the clearest juice is the one to which the proper proportions of tannin and gelatin were added.
The quantities of tannin and gelatin to use for 380L-batches of apple juice are then found by referring to the table below. For smaller amounts of cider, proportionate amounts of tannin and gelatin are used. For example, if bottle 3 showed the clearest juice at the end of 10 minutes, 35 gm of tannin and 126 gm of gelatin should be added to each 380L of juice; for 190L, one-half these amounts should be added.
AMOUNTS OF GELATIN AND TANNIN TO BE USED FOR 100 GALLONS APPLE JUICE
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Bottle No. 1
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Bottle No. 2
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Bottle No. 3
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Bottle No. 4
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|
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Tannin (grams)
|
35
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35
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35
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35
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Gelatin (grams)
|
42
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84
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126
|
252
|
 |
Apple juice flowchart |
According to this procedure, the actual clarification of apple juice is carried out by first stirring a solution into the apple juice containing the proper amount of tannin. A few minutes later, the correct quantity of gelatin, dissolved in hot water, is added and stirred constantly. It is essential that the juice is very thoroughly stirred after the addition of the treating chemicals. After standing overnight, the clear supernatant liquids are drawn off and filtered. In some plants, the liquid is not separated from the sludge since the filter retains the sludge. This speeds up the operation and eliminates waste from discarding juice with the sludge.”
The success of the tannin-gelatin method of clarification is partially due to the operator’s experience. Too much gelatin in the juice can slow filtering and cause the finished juice to cloud or precipitate upon storage.
Clarification of Lemon Juice**
After reaching each incubation time (35°C, 15 min–165 min), the enzyme-treated lemon juices were immediately heated at 50°C. Bentonite, gelatin, and kieselsol had negative, positive, and negative charges, respectively, and were added to lemon juice for clarification. Bentonite (SIHA-Puranit UF), gelatin (SIHA-Gelatin Fine Granules type A, 80–100 bloom), and kieselsol (Levasil 200, SiO2, 30% Food Grade) were supplied by Targıd Inc. (Turkey). Preliminary experiments were carried out for the amounts of bentonite (5%), gelatin (1%), and kieselsol (Levasil 200/30%) which were determined as 35 L/ton, 2 L/ton, and 2 L/ton lemon juice, respectively. The lemon juice was incubated (35°C) for 2 hours by mixing 5 d (110 rev/min). Initially, the fining agents were stirred and then incubated for aggregation without stirring to ensure homogeneous distribution.
The lemon juice was clarified using a laboratory-scale filtration unit with a filter paper plate (MinifiltroF6, 200 × 200 mm, Enotecnica Pillan Snc, Italy). Clarified lemon juices were concentrated in a rotary evaporator under a vacuum (Heidolph Basic Eei-VAP HL, Germany) at 60°C. The clarified juice was concentrated using a rotary vacuum evaporator until it reached about 45° brix. Each experiment was carried out in three replications. Samples of concentrated clear lemon juice were stored at −25°C for 180 days in brown bottles and were analyzed in two-month intervals.
* FAO.org
Author :
There are many questions about the usage of gelatin, enzymes, and alcohol in juice production, especially in the clarification process for pasteurizing. Most of the time, the gelatin used is a pig source, and alcohol also needs to be checked. Hence, it is important to check the juices and consume only products with Halal certification. See the video at 0:53 for evidence of how gelatin is widely used for juices as a processing aid.
Copy Video and Share: https://youtu.be/SWEO0JzzSN4?t=53s
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