Abstract:
The present invention is directed to field test kits, methods, and compositions for the field detection of monosodium glutamate (MSG) and related materials in foodstuffs and drinks. The field test kit consists of a reaction chamber, a closed reaction vessel containing encapsulated chemicals, and a means of providing heat to the reaction chamber, all housed in a convenient construction. The function of the encapsulated chemicals is to produce a colorimetric reaction with MSG at very low concentrations.

Description:
FIELD OF THE INVENTION 
     The present invention relates to the rapid and convenient determination of the presence of monosodium glutamate (MSG) and related compounds in foodstuffs and drinks in a non-laboratory environment. 
     BACKGROUND OF THE INVENTION 
     Glutamic acid, also known as α-aminoglutaric acid or 2-amino pentanedioc acid, is a nonessential amino acid with the chemical formula COOH(CH2)2CH(NH2)COOH (FW=147.13 g, CAS No. 56-86-0). The naturally occurring form is the L(+)-glutamic acid (mp=205° C. with decomposition). It is usually found in foodstuffs and drinks as the sodium salt, monosodium glutamate, also known as sodium glutamate or MSG, with the chemical formula COOH(CH2)2CH(NH2)COONa (FW=187.14 g, CAS No. 6106-04-3). MSG (mp=232° C. with decomposition). MSG is used as a flavor enhancer in foodstuffs and drinks at about 0.3%. 
     Many people have an allergic or adverse reaction to MSG in food. Symptoms vary in type and magnitude but can include rashes and swelling of the throat. Tolerance levels vary person to person but sensitive people can react to 5 g of MSG, whereas non-sensitive people can tolerate up to 25 g. MSG is found in more than Chinese cooking. It occurs naturally in parmesan cheese, tomatoes, spinach, mushrooms, and seaweed. It is also in tuna and some ice creams. The issue is that it is also hidden in foods as a flavor enhancer. If you are Type II diabetic, then the MSG can raise your blood pressure. MSG is especially bad for anyone with Renal Failure (kidney failure). 
     MSG is known as monosodium glutamate, glutamate, glutamic acid, Accent®, Ajinomoto®, hydrolyzed oat flour, Glutavene®, and L-cysteine. MSG is almost always present in glutamate, yeast extract, hydrolyzed protein, glutamic acid, calcium caseinate, sodium caseinate, yeast food, gelatin, textured protein, yeast nutrient, and autolyzed yeast. MSG is often found in natural beef flavorings, stock, broth, malt extract, soy sauce, and soy protein. So although a chef might not deliberately add MSG to his cuisine, it may be added accidentally in a broth or other ingredient. 
     Since it is very difficult to determine what foodstuffs might actually contain MSG, there is a strong need for a field test kit that can determine the presence of MSG in foodstuffs and drinks quickly and efficiently in a non-laboratory environment such as a restaurant or other dining establishment. 
     A survey of the literature indicated very few chemical systems that would be appropriate to use in the present invention. It was decided that a colorimetric change would be required for an inexperienced person to determine a positive reaction to MSG. A spot reaction test was found that was reported to be effective at very low levels of an alpha-amino acid. 1    
     This spot test method involves the detection of an α-amino acid through condensation with pyridine-2-aldehyde to form a Schiff base (an imine). Pyridine is used to ensure the availability of the amino group for reaction by neutralization of the carboxylic acid group. Cobalt nitrate is used as a chelating agent to give a colored species that can be visually determined. This method requires mixing a reagent and then heating the reagent with the sample for one to three minutes. 
     There is no reported data regarding the reaction with MSG. However, the method is very sensitive to α-amino acids. The following materials tested positive: 3 γ cystine, 3 γ cysetine, 2.5 γ methionine, 5 γα-alanine, 2 γ lysine, 1 γ glycine, 3 γ tyrosine, 1 γ L-leucine, 5 γ aspartic acid, and 5 γ asparagine. A positive response was also obtained for monoiodo-L-tyrosine, valine, citrulline, arginine, phenylalanine, tryptophan, and 2-amino-n-octanoic acid. 
     The issue with the reagents selected for the colorimetric reaction is the short shelf-life once the reagent is prepared by mixing the pyridine-2-aldehyde solution and the cobalt nitrate solution. It is reported that the shelf life is only one week which would make this system unacceptable for a field test kit. 
     In U.S. Pat. No. 5,824,554 a dining mat, such as a doily, composed of absorbent material and small spots of applied reagents was used to determine the presence of allergenic substances. 2  In use, food is applied to the reagents on the dining mat, and the reagent changes its appearance indicating the presence of the allergenic substance in the food product. The advantage of this method is that only a small sample of food is required and the food is not contaminated by the testing. However, although MSG was listed as an allergenic material, there was no mention of any reagent system that might allow for the detection of MSG in the food. Since the spot test requires the use of a liquid reagent, namely pyridine-2-aldehyde, this dining mat method using the reagents of the spot test method will not work for MSG. At best, the dining mat method will suffer the same short shelf-life issue as the mixture of reagents from the spot test. 
     Therefore, a solution to this shelf-life issue is provided by this invention while maintaining the advantages of convenience of use and no food contamination found in the prior art. An encapsulating material is needed to keep the reactive chemicals separate until they are required to react with the foodstuff. Since the colorimetric reaction occurs at near boiling water temperature, it is desirable to have this encapsulating material melt below that temperature. It has been surprisingly found that a low melting paraffin wax can function as an encapsulating material. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to field test kits, methods, and compositions for the field detection of monosodium glutamate (MSG) and related materials in foodstuffs and drinks. The field test kit  10  is small enough for someone to carry the device in a jacket pocket or purse. It is simple, safe, and convenient to use in a public area such as a restaurant or other dining establishment. The field test kit  10  consists of a reaction chamber  12 , a closed reaction vessel  14  containing encapsulated chemicals  16 , and a means of providing heat to the reaction chamber  12 , all housed in a convenient construction  36 . The reaction chamber  12  consists of a tube which is the correct size to hold the reaction vessel  14 . The closed reaction vessel  14  can be a glass vial  22  with a plastic cap  24 . In order to use the reaction vessel  14 , the plastic cap  24  is removed, a small sample of the test food  34  is inserted into the reaction vessel  14  using a fork, spoon, or straw, and the plastic cap  24  is replaced. The function of the encapsulated chemicals  16  is to produce a colorimetric reaction with MSG at very low concentrations. The present invention comprises heating the reaction chamber  12  electrically using a nichrome wire  20 , a battery pack  26 , a switch  32 , and an LED indicator  30 . Enough turns of nichrome wire  20  are applied to the reaction chamber  12  to produce a temperature of about 200° F. in the reaction vessel  14 . Materials of the housing construction  36  include plastics. 
    
    
     
       DESCRIPTION OF THE DRAWING 
       A front view of the invention is shown in  FIG. 1 . The field test kit  10  consists of there basic elements of a reaction chamber  12 , a closed reaction vessel  14  containing encapsulated chemicals  16  and  18 , and a means of providing heat to the reaction chamber  12 , all housed in a convenient construction  36 . An electrical circuit consisting of a battery pack  26  with AA batteries  28 , nichrome wire  20  wrapped around the reaction chamber  12  which in turn provides heat to the closed reaction vessel  14 . The closed reaction vessel  14  typically consists of a glass vial  12  with a plastic cap into which a sample of food  34  can be placed for testing. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention comprises a field test kit  10  for detecting the presence of monosodium glutamate (MSG) in foodstuffs and drinks. The field test kit  10  comprises a reaction chamber  12 , a closed reaction vessel  14  containing encapsulated chemicals  16 , and a means of providing heat to the reaction chamber  12 , all housed in a convenient construction  36 . The construction  36  is made of plastic such that there are three compartments. The reaction chamber  12  housed in the top compartment comprises a brass tube about 0.5 inches in diameter and about one inch in length insulated with polyester film and wrapped with eight turns of 21-gauge nichrome wire  20 . The closed reaction vessel  14  containing encapsulated chemicals  16  comprises a 2 ml glass vial  22  with a plastic cap  24  with a center section of silicone. The encapsulated chemicals  16  consist of an aqueous solution of 2-pyridine-carboxyaldehyde and sodium hydroxide and separately an aqueous solution of cobalt nitrate. The encapsulating material  18  is a low melting paraffin wax (mp 120° F.). In order to use the reaction vessel  14 , one reaction vessel  14  is removed from the bottom storage compartment, the plastic cap  24  is removed; a very small sample of the test food  34  is inserted into the reaction vessel  14  using a fork, spoon, or straw; and the plastic cap  24  is replaced. The reaction vessel  14  is then placed in the reaction chamber  12  such that the plastic cap  24  extends above the top compartment of the housing so as to allow easy removal. The encapsulated chemicals  16  react with the MSG in the test food  34  when heated for up to three minutes to produce a colorimetric change which can be observed visually as a change from yellow to dark red or blue once the reaction vessel  14  is removed from the reaction chamber  12 . The reaction chamber  12  is heated electrically by applying a current to a nichrome wire  20  wrapped around the brass tube using a battery pack  26  of four AA batteries  28  found in the middle compartment and a push switch  32  and an LED  30  protruding from the top compartment on the right hand side. The reaction vessel  14  reaches about 200° F. in about two to three minutes causing the encapsulating material  18 , such as wax, to melt and allowing the encapsulated chemicals  16  to mix and react with the test food  34  sample containing MSG. The reaction vessel  14  can be removed temporarily and shaken to increase mixing. A positive test is a color change from yellow to dark red or blue. After the test is complete, the reaction vessel  14  is placed on a level surface and allowed to cool to room temperature. The encapsulating material  18 , such as wax, floats to the surface of the reaction vessel  14  due to its lower density as it cools and solidifies forming a barrier on the surface. Thus, the chemicals contained therein are protected from human contact, making disposal convenient and safe. 
     In one embodiment, the present invention provides a method for determining the presence of MSG in foodstuffs and drinks comprising the steps of: removing a reaction vessel  14  from the storage compartment of the field test kit housing construction  36 ; opening the reaction vessel  14  by removing the cap  24  and then introducing a small food sample  34  into a reaction vessel  14  containing encapsulated chemicals  16 ; closing the reaction vessel  14  and placing the reaction vessel  14  in a reaction chamber  12 ; heating the reaction chamber  12  to about 200° F. for 1 to 3 minutes; and visually observing the color change in the reaction vessel  14 . The color change is usually from yellow to a deep red or purple. 
     In one embodiment of the housing construction  36 , the housing is constructed of polystyrene panels into three compartments consisting of a bottom storage compartment for reaction vessels  14 ; a middle compartment holding 4 AA batteries  28 ; a top compartment containing the reaction chamber  14 , push-button switch  32 , and a light-emitting diode  30 , and a cover door allowing access to the middle and bottom compartments. 
     In another embodiment of the housing construction  36 , ABS plastic is used in place of polystyrene to build the three compartments. 
     In another embodiment of the housing construction  36 , polycarbonate plastic is used in place of the polystyrene to build the three compartments. 
     In another embodiment of the housing construction  36 , the 4 AA batteries  28  are replaced with a rechargeable 6-volt battery pack. 
     In another embodiment of the housing construction  36 , the panels used to construct the three compartments can be replaced with an injection molded structure. 
     In another embodiment of the housing construction  36 , the push-button switch  32  is replaced with a push-and-hold switch which would close the circuit for 1 to 3 minutes. 
     In one embodiment of the reaction chamber  12 , a metal tube is used to provide a holder for the reaction vessel  14 . The reaction chamber  12  needs to fit the reaction vessel  14  snuggly so as to be able to transfer heat efficiently. It was found that a 0.5 inch (outside diameter) brass tube fitted perfectly. About a one inch long piece was sufficient to cover the glass portion of the reaction vessel  14  (glass vial  22 ) and allow the cap  24  to protrude out of the heated area. However, the nichrome wire  20  cannot come into direct contact with an electrical conductor. Otherwise, the desired reaction chamber  12  temperature is not achieved. Hence, the exterior of the brass tube was electrically insulated with polyester film. 
     In another embodiment of reaction chamber  12 , a ceramic tube is used to provide a holder for the reaction vessel  14 . The reaction chamber  12  needs to fit the reaction vessel  14  snuggly so as to be able to transfer heat efficiently. The advantage of a ceramic tube over a metal tube is that the ceramic tube is not electrically conducting and the nichrome wire  20  used for heating can be incorporated directly into the ceramic tube. 
     In one embodiment of the reaction vessel  14 , a clear glass vial  22  about 2 ml in volume is used. The vial  22  contains encapsulated chemicals  16  consisting of an aqueous solution of 2-pyridine-carboxyaldehyde and a base such as sodium hydroxide and separately an aqueous solution of cobalt nitrate. 
     In another embodiment of the reaction vessel  14 , the vial  22  contains encapsulated chemicals  16  consisting of an aqueous solution of 2-pyridine-carboxyaldehyde and separately an aqueous solution of cobalt nitrate and a base such as pyridine. 
     In another embodiment of the reaction vessel  14 , the vial  22  contains encapsulated chemicals  16  consisting of an aqueous solution of 2-pyridine-carboxyaldehyde and pyridine and separately an aqueous solution of cobalt nitrate. 
     In another embodiment of the reaction vessel  14 , the vial  22  contains encapsulated chemicals  16  consisting of an aqueous solution of 2-pyridine-carboxaldehyde and sodium hydroxide solution and separately an aqueous solution of cobalt nitrate. 
     In another embodiment of the reaction vessel  14 , the encapsulated cobalt nitrate is replaced with any water soluble cobalt salt such as cobaltous acetate, cobaltous ammonium sulfate, cobaltous bromide, cobaltous chloride, cobaltous iodide, or cobaltous sulfate. 
     In another embodiment of the reaction vessel  14 , the glass vial  22  contains encapsulated chemicals  16  consisting of an aqueous solution of 2-pyridine-carboxaldehyde and sodium hydroxide solution and separately cobalt nitrate powder. 
     In another embodiment of the reaction vessel  14 , the encapsulated chemicals  16  are prepared by surrounding each individual chemical mixture with an encapsulating material  18  consisting of a low melting and water insoluble material such as paraffin wax with a melting point of less than about 200° F. The paraffin wax does not react with the encapsulated chemicals  16 . The reaction vessel  14  is first coated with a thin layer of paraffin wax by melting the wax and adding the molten wax to the reaction vessel  14  and allowing the wax to cool in contact with the walls and bottom of the reaction vessel  14  while the reaction vessel  14  is maneuvered so as to coat all the inner surfaces of the reaction vessel  14 . Then the required amount of the first chemical mixture consisting, for example, of an aqueous solution of 2-pyridine-carboxaldehyde and a base such as sodium hydroxide is added. Then more molten wax is added to the reaction vessel  14  to seal this chemical mixture entirely. Thus, the first chemical mixture is fully encapsulated in the bottom of the reaction vessel  14 . Next the second chemical mixture consisting, for example, of aqueous cobalt nitrate, is added to the reaction vessel  14 . More molten wax is added to the reaction vessel  14  to seal this second chemical mixture entirely. Thus, the second chemical mixture is fully encapsulated on top of the first encapsulated chemical mixture. Therefore, the two chemical mixtures are kept separate in the reaction vessel  14  and not allowed to react. The cap  24  is then added to close the reaction vessel  14 . 
     In another embodiment of the reaction vessel  14 , the encapsulated chemicals  16  are prepared by containing each individual chemical mixture within a thin glass ampoule. The thin glass ampoule can be of any shape including a tube such as a melting point tube. For example, a chemical mixture of an aqueous solution of 2-pyridine-carboxaldehyde and a base such as sodium hydroxide is placed in a glass ampoule and sealed. Similarly, for example, aqueous cobalt nitrate is placed in a glass ampoule and sealed. One ampoule of each chemical mixture is then added to one reaction vessel  14  comprising a clear plastic vial. After addition of the test food  34  and sealing with the cap  24 , the ampoules are broken by flexing the reaction vessel  14  so as to bend the ampoules causing them to rupture. Therefore, the two chemical mixtures are kept separate in the reaction vessel  14  and not allowed to react until needed for the test. 
     In one embodiment of the reaction chamber  12 , nichrome wire  20  is used to heat a brass tube using an electrical circuit consisting of a battery pack  26 , a push-button switch  32 , and an LED indicator  30 . The nichrome wire  20  is insulated from the brass tube using polyester film. 
     In another embodiment of the reaction chamber  12 , the nichrome wire  20  is insulated from the brass tube with parchment paper. 
     In another embodiment of the reaction chamber  12 , a ceramic tube can be used in place of the brass tube. The nichrome wire  20  can be embedded directly into the ceramic before it is thermally cured. 
     In another embodiment of the reaction chamber  12 , other heat sources are used to heat the reaction vessel  14 . In the absence of a complete field test kit  10 , there are other options for heating the reaction vessel  14 . One option is to hold the reaction vessel  14  under a stream of hot water. Another option is to place the reaction vessel  14  into a container of near boiling liquid such as water, hot coffee, or tea. Another option is to heat the reaction vessel  14  with hot air such as using a hair dryer. Another option is to heat the reaction vessel  14  with an open flame such as using a cigarette lighter. Another option is to use microwave radiation to heat the reaction vessel  14 . It may take longer for the chemical reaction to occur using alternative heat sources, but the end result will be the same as if the reaction vessel  14  was electrically heated. 
     EXPERIMENTAL 
     The following examples are provided in order to demonstrate and further illustrate certain preferred embodiments and aspects of the present invention and are not to be construed as limiting the scope thereof. 
     In the experimental disclosure which follows, the following abbreviations apply: CAS (Chemical Abstracts Service), cc (cubic centimeter), M (molar), g (grams), MSG (monosodium glutamate, glutamic acid, and any other form that this chemical may take), % (percentage), ml (milliliter), mg (milligram), MP (melting point), FP (freezing point), α (alpha), FW (formula weight), sec (seconds), ° F. (degrees Fahrenheit), ° C. (degrees Celsius), γ (microgram), LED (light emitting diode), and BP (boiling point). 
     2-pyridine-carboxyaldehyde (C6H5NO, FW=107.11, CAS No. 1121-60-4) is available from Aldrich Chemical. This liquid has a FP of 54° C. and a BP of 178-181° C. The density is 1.121 g/cc. It is soluble in water. 
     Cobalt nitrate is available as a hexahydrate from Aldrich Chemical (FW=291.03 g, CAS No. 10026-22-9). This solid has a MP of 56° C. and is soluble in water. 
     Example 1 
     Selection of Chemicals for Colorimetric Reaction with MSG 
     A solution of pyridine-2-aldehyde (FW=107.11 g, CAS No. 11221-60-4) was prepared in water at 0.5% concentration by dissolving 0.05 g of pyridine-2-aldehyde in 10 ml deionized water. A 0.1 M solution of cobalt nitrate was prepared by dissolving 0.291 g of cobalt nitrate hexahydrate (FW=291.03 g, CAS No. 10026-22-9) in 10 ml deionized water. A reagent was made by mixing five drops of the pyridine-2-aldehyde solution with one drop of the cobalt nitrate solution into a 10 ml glass test tube. To this mixture was added one drop of pyridine to ensure that the amino group of the alpha-amino acid was free to react. A test sample (only about 0.5 mg of material) of an alpha-amino acid (or other material) was then added to the test tube. If the sample was very dry, a few drops of water were also added. The test tube was capped with a plastic cap and heated in nearly boiling water for three minutes. A color change was indicative of the presence of an α-amino acid. The color change can vary from a yellow to a deep red to a deep violet. Table 1 gives the test results for several test samples. A 0.039 M standard solution was made of MSG (FW=187.14 g) by dissolving 0.066 g of MSG technical grade in deionized water. 
     
       
         
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Test Results From Boiling Water 
               
             
          
           
               
                   
                   
                 Drops of 
                   
                   
               
               
                 Test 
                   
                 Reagent/Drops 
                 Resulting 
                 Test 
               
               
                 No. 
                 Test Material 
                 of Pyridine 
                 Color 
                 Result 
               
               
                   
               
             
          
           
               
                 1 
                 MSG, technical grade 
                 1/1 
                 Light purple 
                 Positive 
               
               
                 2 
                 MSG, technical grade 
                 2/2 
                 Dark blue 
                 Positive 
               
               
                 3 
                 MSG, technical grade 
                 2/2 
                 Medium blue 
                 Positive 
               
               
                   
                 Standard solution 
               
               
                   
                 (2 drops) 
               
               
                 4 
                 Beef and Gravy 
                 2/2 
                 Purple 
                 Positive 
               
               
                   
                 Baby Food 
               
               
                 5 
                 Water 
                 2/2 
                 Yellow 
                 Negative 
               
               
                 6 
                 Starch 
                 2/2 
                 Yellow 
                 Negative 
               
               
                 7 
                 Aspartame 
                 2/2 
                 Light yellow 
                 Negative 
               
               
                 8 
                 Yellow Mustard 
                 2/2 
                 Yellow 
                 Negative 
               
               
                 9 
                 Canned Chicken 
                 2/2 
                 Clear 
                 Negative 
               
               
                 10 
                 MSG, technical grade 
                 2/2 
                 Purple 
                 Positive 
               
               
                   
                 Standard solution 
               
               
                   
                 (2 drops) 
               
               
                   
               
             
          
         
       
     
     The test method appears to be specific for MSG. A protein or peptide does not interfere. 
     Example 2 
     Encapsulating the Reagents in the Reaction Vessel  14   
     Paraffin wax such as that used for canning and candle making was chosen. The paraffin wax was melted in a pan over hot water. The melt temperature was measured to be about 160° F. using an IR thermometer. A few drops of the molten wax was transferred to a 2 ml glass vial  22  and allowed to coat the vial  22  on the bottom and midway up the sides as the wax cooled while the vial  22  was rotated. Five drops of the pyridine-2-aldehyde reagent solution was placed in the 2 ml glass vial  22 . A few drops of molten wax were used to encapsulate this first reagent solution. Similarly, two drops of the cobalt nitrate reagent solution and two drops of pyridine were transferred to the vial. Then a few drops of molten wax were added. The wax was allowed to cool and encapsulate this second reagent solution. The vial  22  was closed with a plastic cap  24  with a silicone seal. After many weeks storage at room temperature, the layers were still separate. 
     In a separate experiment a low temperature paraffin wax (128° F.) was used as the encapsulating material  18 . This paraffin wax was melted in a pan over hot water. The temperature of the melted wax was measured to be about 170° F. using an IR thermometer. A few drops (about 0.5 ml) of the molten wax was transferred to a 2 ml glass vial  22  and allowed to coat the vial  22  on the bottom and midway up the sides as the wax cooled while the vial  22  was rotated. Five drops of the pyridine-2-aldehyde reagent solution were placed in the 2 ml glass vial  22  along with 1 drop of 0.2 M sodium hydroxide solution. About ten drops of molten wax were used to encapsulate this first reagent solution. Similarly, three drops of the cobalt nitrate reagent solution were transferred to the vial  22 . Then about ten drops of molten wax were added. The wax was allowed to cool and encapsulate this second reagent solution. It was noted that the wax in the heating pan began to solidify at about 128° F. After storage for over three months at room temperature, the layers in the vials were still separate. 
     Example 3 
     Selection of Materials for Reaction Chamber  12   
     Since the concept is to construct a small device that will fit into a purse or pocket, a 2 ml clear glass vial  22  with rubber septum cap  24  was chosen as the reaction vessel  14  due to its small size and easy access. Therefore, the reaction chamber  12  needs to fit this vial  22  snuggly so as to be able to transfer heat efficiently. It was found that a 0.5 inch (outside diameter) brass tube fitted perfectly. About a one inch long piece was sufficient to cover the glass portion of the vial  22  and allow the cap  24  to protrude out of the heated area. However, the nichrome wire  20  cannot come into direct contact with an electrical conductor. Otherwise, the desired reaction chamber  12  temperature is not achieved. Hence, the exterior of the brass tube was electrically insulated with polyester film. Other suitable materials include paper or ceramic. 
     Other materials were evaluated for construction of the reaction chamber  12  and were also found to be acceptable including aluminum foil molded around the glass vial  22 . Also, a ceramic material was cast around the vial  22  with nichrome wire  20  present. The ceramic (about 0.125 inches thick) was cured by heating in an oven at 275° F. for 15 minutes. 
     Example 4 
     Selection of Heating Source for Reaction Chamber  12   
     The objective was to heat the reaction chamber  12  to about 200° F. to allow the wax to melt and allow the individual reactive ingredients to mix with the food sample  34 . It was found that about 8 wraps of 21-gauge (0.0285 inch diameter) nichrome wire  20  (about 13 inches including leads) could supply the desired heat when powered by four AA batteries  28  as shown in Table 2. A brass reaction chamber  12  with polyester film insulation was used. A 2 ml clear glass vial  22  with an encapsulated chemical  16  of five drops of pyridine-2-aldehyde solution and an encapsulated chemical  16  of one drop of cobalt nitrate solution with one drop of pyridine was used as the reaction vessel  14 . Two drops of the standard MSG solution were added and the vial  22  was sealed with a plastic cap  24  with a rubber septum center. The push-button switch  32  activated the heating circuit as indicated by the glowing LED  30 . The temperature of the reaction chamber  12  was measured with an IR thermometer versus time as recorded in Table 2. 
     
       
         
               
             
               
               
               
             
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Heating Rate Study 
               
             
          
           
               
                   
                 Time (sec) 
                 Temperature (° F.) 
               
               
                   
                   
               
             
          
           
               
                   
                 0 
                 82 
               
               
                   
                 10 
                 120 
               
               
                   
                 20 
                 134 
               
               
                   
                 30 
                 150 
               
               
                   
                 60 
                 160 
               
               
                   
                 75 
                 179 
               
               
                   
                 90 
                 182 
               
               
                   
                 120 
                 196 
               
               
                   
                 150 
                 209 
               
               
                   
                 180 
                 211 
               
               
                   
                   
               
             
          
         
       
     
     The wax began to melt at about 150° F. and continued to melt as the temperature increased allowing mixing of the reagents with the sample. The rubber septum in the plastic cap  24  bulged slightly indicating that the sample was getting warm. The color change was from yellow to a medium red. 
     Example 5 
     Construction of Housing to Hold Components of Field Test Kit  10   
     Polystyrene sheets were cut to form a box with internal dimensions of about 3.5 inches wide by 3 inches tall by 1.5 inches deep. Three compartments were constructed by adding a shelf at one inch from the bottom and a shelf at one inch down from the top. The top compartment housed the reaction chamber  12  such that the 2 ml clear glass vial cap  24  sticks out a hole in the housing  36  above the brass tube which is centered in the left side of the compartment. The brass tube was insulated with polyester film. Next to this hole with the vial cap  24  protruding on the top side of the top compartment was placed a light emitting diode  30 . Also, a push-button switch  32  was allowed to protrude out the top compartment on the right side of the housing  36 . The center compartment housed a four pack  26  of AA batteries  28  equipped with a 9 volt battery terminal. The batteries  28  were wired through the switch  32  to the nichrome wire  20  on the reaction chamber  12 . The bottom compartment served as a storage compartment for the reaction vessels  14  (2 ml glass vials  22  containing the encapsulated chemicals  16 ). This bottom compartment also serves to hold used vials  22 . The top compartment was sealed off to prevent anyone touching the hot reaction chamber  12  or the wires to the switch  32  and LED  30 . However, the bottom two compartments were accessible through a hinged door with clasp or a sliding door so as to allow removal and replacement of batteries  28  and reaction vessels  14 . 
     From the above Examples, it is clear that the present invention represents a convenient and inexpensive method for the field testing of foodstuffs and drinks for the presence of MSG. 
     In summary, the present field test kit invention provides a novel approach to field testing for the presence of MSG in foodstuffs and drinks. Advantages of this invention include: (1) convenience of handling, (2) fast registration of results, (3) easy interpretation of results, and (4) a boon to public health. 
     REFERENCES CITED 
     
         
         1. F. Feigl, Vinzenz Anger, and R. E. Oesper, “Spot Test in Organic Analysis”, Elsevier Scientific Publishing Company, New York, 1966, p. 370. 
         2. F. M. McKay, “Detection of allergenic substances in food products”, U.S. Pat. No. 5,824,554 (Oct. 20, 1998).