Glucosinolate Test That Can Be Used To Differentiate Between Canola Meal (OK to Feed Livestock) and Rapeseed Meal (NOT OK to Feed to Livestock)
Introduction by Roy Chapin
Previously I have written concerning the advisability of feeding canola meal to livestock in Ukraine. In support of feeding canola meal in Ukraine, I wrote a 15 page article called, "Guidelines for Feeding Canola Meal to Dairy and Beef Cattle, Swine and Poultry" as well as a shorter brochure on the same topic.
Canola is a new word (not found in Russian or Ukrainian language dictionaries) coined from the words, "CANadian Oil Low Acid" - "CANOLA". The Canadians were the first to develop such a product by the selective breeding of rapeseed. Now, worldwide, the word "canola" signifies any rapeseed that is low in both erucic acid and glucosinolates. In Europe such a product may be referred to as "feed grade oil seed rape" or some similar term to differentiate it from conventional rapeseed meal.
Canola meal can be used as an inexpensive (usually) and desirable source of protein for livestock and poultry. Since many animals in Ukraine are deficient in dietary protein, if canola meal (high in protein) were used in feed rations according to recommended guidelines, it would be expected to increase substantially the productivity of milk, meat and eggs and to create added wealth.
If canola were fed, besides improving animal performance, it would make a stronger market for this by-produce of raising canola for its oil and thus economically help the farmers who raise canola. Canola is a product that can be raised in Ukraine (particularly Western Ukraine) by private farmers without state involvement (impediment!) in the raising and/or marketing. Canola seed is an international commodity with ready markets in Europe. Vegetable oil presses are inexpensive enough that an association of private farmers (such as an agricultural processing and marketing cooperative) or a private entrepreneur could own and operate one for mechanically separating canola into oil and meal. This would capture the added value from processing for private interests and keep this farm product out of state channels and control.
Canola oil is an international commodity while canola meal could be fed locally for the benefit of local livestock feeders. Increased feeding of canola meal would create a private market for the canola growers who produce, process and sell it. The raising and processing of canola is an attractive economic alternative (to wheat, sugar beets and other crops likely to be controlled by the government). Getting canola raising technology out to the potential growers of canola should be a priority for Western programs aimed at helping private farmers in those areas of Ukraine where canola grows well. In addition, the benefits from feeding canola meal should be publicized to private livestock and poultry feeders along with supplying guidelines on how to feed it.
Those are available for the asking.
There is one major concern in feeding canola meal and that is whether it is really "canola meal" or is it its close cousin, "rapeseed meal". Canola seed is low in erucic acid and glucosinolates while rapeseed is high in both. Erucic acid and glucosinolates are toxic to animals but have desirable uses (particularly erucic acid) in industry.
Erucic acid is present in the oil while glucosinolates are present in the meal, therefore it is primarily the glucosinolate level of the meal that we're concerned about and therefore interested in testing before feeding what we think is "canola meal".
Since quality control and labeling that would indicate clearly to the customer whether he/she was buying canola meal or rapeseed meal may not be obvious, the need for a quick and easy test to differentiate canola meal from rapeseed meal is desirable. Feeding rapeseed meal to animals can be dangerous to their health as opposed to the benefit to them from feeding canola meal.
Attached is a chemical method that can be used to test the glucosinolate level of canola meal to be certain that it is safe to feed. This method was supplied by the Canadian Grains Commission Grain Research Laboratory. Sending this method to you is main reason for this communication.
I hope that you will find this information on how to test for glucosinolates in canola meal of benefit to you and to those who raise livestock and are looking for an economical source of dietary protein.
Roy Chapin, Ph.D., Animal Nutritionist, Land O'Lakes Farmer to Farmer Volunteer - L'viv, Ukraine.
11145 Chapin Lane, Amity, Oregon 97101
E-mail: <[email protected]>
GLUCOSINOLATE ESTIMATION IN CANOLA/RAPESEED MEAL WITH GLUCOSE SENSITIVE STRIPS
Method of the Canadian Grain Commission Grain Research Laboratory
1. SCOPE AND FIELD OF APPLICATION
This test describes a method for estimating glucosinolate levels in canola or rapeseed meals. The method is used to distinguish canola quality meal from non-canola quality meal (i.e. rapeseed meal).
2. SAFETY AND HANDLING
2.1. Hazards. (Consult MSDS Sheets).
2.2. The inhalation of the dusty activated charcoal powder is a moderate health hazard.
2.3. Activated charcoal is flammable.
2.4. Handling and Storage.
2.5. Use a dust mask to avoid breathing in the charcoal powder.
2.6. Store charcoal in glass container away from sources of ignition.
2.7. Waste Disposal.
2.8. After testing, plastic weighing boats and charcoal paste can be disposed of by placing in a plastic bag and then in a trash can.
3.1. Canadian Journal of Plant Science 55:191 (1975).
4.1. The Canadian Feed Regulations define canola as containing "less than 30 micromoles of any or any mixture of 3-butenyl glucosinolate, 4-pentenyl glucosinolate, 2-hydroxy-3-butenyl glucosinolate and 2-hydroxy-4-pentenyl glucosinolate per gram of air-dried, oil-free solid."
5.1. An enzyme, myrosinase, in the presence of water, breaks down the glucosinolate molecules into their component parts, one of which is glucose (a type of sugar). The Tes Tape test is specific for glucose; other sugars will not react with the tape. Oilseed meals have a low content of free glucose. The amount of glucose detected by the Tes Tape indicates the level of glucosinolates present in the sample.
5.2. The Tes Tape paper is impregnated with the enzymes glucose oxidase and peroxidase and the oxidizable chromagen (dye) orthotolidine. Glucose reacts with the glucose oxidase to produce gluconic acid and hydrogen peroxide.
The hydrogen peroxide then reacts with peroxidase to turn the orthotolidine from colorless to blue. With the yellow dye in the paper, the possible color range of the test is from yellow to light green to deep blue. If no glucose is present, the tape maintains its original color.
6.1. Tes Tape (Glucose enzymatic test strip). Eli Lilly and Company; 4m (150 inches) per package. (Note: many other glucose kits prepared for diabetic testing will also work).
6.2. Charcoal, activated; powder.
6.3. Myrosinase solution (0.400 g myrosinase enzyme (Biocatalysts Limited, Main Ave. Treforest Industrial Estate, Pontypridd, Mid Glam, C537 5UT, United Kingdom FAX +44 1443 84124) in 100 ml Tris-HCL Buffer (pH 7.0).
6.3.1. Tris-HCL Buffer. Dissolve 1.6 g trizma base and 13.7 g trizma HCL in 950 ml water. Adjust pH to 7.0 and volume to 1 L.
7.1. A blade-type mill, coffee mill, or equivalent.
7.2. Plastic weighing boats; (e.g. 100 ml capacity) or other suitably sized clean dishes or trays, preferably disposable.
7.3. Whatman No. 1 Chromatography paper; 2cm (3/4 inches) wide.
7.4. Measuring spoon; 10 ml (one teaspoon).
7.5. Measuring spoon; 5 ml (half teaspoon).
7.6. Clock with a second function.
7.7. Cleaning brush; for cleaning out grinder.
8.1. Ensure representative, well-mixed samples are selected.
9.1. Preparation of the test sample. Separate major impurities such as stones, straw and other grains.
9.2. Test portion.
9.2.1. The test portion shall be representative of the analysis sample.
9.2.2. Transfer 7-10 g (3 teaspoons) of the test sample to the grinder and grind using two 15 second bursts; gently inverting and shaking the grinder between bursts to prevent caking of the sample.
9.3. Extraction and Analysis of Glucose (Glucosinolates).
9.3.1. Transfer 0.8 g (one level half-teaspoon) of mixed ground meal into the plastic weighing boat.
9.3.2. Add 0.8 g (one level half-teaspoon) of activated carbon powder and mix well.
9.3.3. Add 5ml of myrosinase solution and blend to a smooth paste. Allow paste to sit (react) for 2 minutes timing with a clock.
9.3.4. Lay two lengths (7cm) of chromatography paper on the surface of the mixture, allow paper to absorb the liquid (5 10 seconds).
9.3.5. Lay 5 cm of Tes Tape paper on top of each moistened chromatography strip and allow to sit (react) 3 minutes timing with a clock.
9.3.6. Remove each test strip, lay on a piece of white paper, and compare the shade of color to the chart on the Tes Tape.
10. EXPRESSION OF RESULTS
10.1. The Tes Tape strips are matched with the color chart readings which indicate the amount of glucose either in percent (0% to 2%) or in relative figures (0 to ++++).
10.2. A color shade lighter than or equal to that shown as 1/10% glucose (0 and + relative scales), indicates the meal is of canola quality.
10.3. A color shade darker than the 1/4% level (the +++ and ++++ relative scales), indicates the meal is not of canola quality.
10.4. A color shade at the 1/4% level (the ++ relative scale) indicates the meal is near the upper level of glucosinolates for canola quality (i.e. 30 µmoles per gram).
10.5. Samples producing a color shade at ++ should always be repeated with another aliquot of the test portion. Check samples of known glucosinolate content should be compared at the same time.
10.6.1. Checking of Tes Tape Activity. The activity of Tes Tape must be checked periodically, especially if it is in use over a period of time. The reliability of a roll of Tes Tape may be checked by dipping a piece in a properly prepared 2% glucose solution. [If a prepared glucose solution is not available, Coca Cola™ from a freshly opened bottle is satisfactory.] After two minutes have elapsed, the reading obtained when the tape is compared with the color chart should be approximately ++++ (2%). If such a reading is not obtained, the tape has deteriorated and should not be used.
10.6.2. Water Blank Test. The water used for the test should be free of glucose. Dip a strip of the Tes Tape into the water to be used for the tests. After two minutes have elapsed, the reading obtained when the tape is compared with the color chart should be 0 (0%).
10.6.3. Use of Check Samples. For comparative purposes, a canola quality meal sample and a non-canola quality sample should be tested at the same time as unknowns. The use of a check sample near the canola glucosinolate level of 30 µmoles/gram is also useful for borderline cases.
S. Zolondek, July 5, 1996.