Resazurin Tablets for Milk Testing vial of 100

Resazurin Test

Resazurin reduction tests have been used to determine the microbial quality of milk and ice cream for many decades. The Resazurin test are used in the grading of raw milk and can be adapted for use at dairy processing facilities, receiving stations, cheese factories, and similar dairy operations. The test is easy to perform and allow simultaneous testing of numerous food samples. The resazurin reduction test is a rapid, inexpensive, and objective test for determining excessive microbial contamination in Milk. This test has been used to assess microbial spoilage of ground beef and sliced raw and cooked meats. It has been applied to frozen meat, frozen poultry pies and vegetables, liquid and dried eggs, and fresh scallops. In addition, it has been applied to heat-processed food products, including frozen meals and precooked frozen shrimp, in which naturally occurring biological reducing agents have been inactivated.

Standard Preparation of Resazurin Solution for Milk Testing

The procedure for making the resazurin test is as follows: Prepare resazurin solution by dissolving one standard resazurin tablet (dye content/ tablet, approximately 2.5 mg,) in 50 ml of cold sterile distilled water which typically yields a 0.005% w/v solution .

Store the solution in a dark bottle preferably refrigerated and prepare fresh as needed ( eg every 8hours for best results) Tablets are designed for convenience and standardisation

Common Test Procedure (1hour test)

• Pipette 10ml of well mixed raw milk sample into a sterile test tube Reductase Tubes 5/10ml (100)
• Add 1ml of prepared resazurin solution
• Stopper the tube Rubber Bung Red Reductase Tube (pack of 20)
• place in the incubator/waterbath and when the temperature reaches 37 deg C +/-0.5 Deg C, Mix by inverting twice gently, over 4seconds
• Start Timer
• After specified time of 1hour for standard grading test in the UK remove and immediately compare the colour using a Lovibond Comparator (Resazurin Testing kit)with the control tube(milk without dye) and the standard disc
• 10min (quick platform/rejection test and 3hour (triple reading) tests can also be performed

Colour of Sample: Quality of Milk

1. Blue (no colour change): Excellent
2. Blue to deep mauve: Good
3. Deep mauve to deep pink: Fair
4. Deep pink to whitish pink: Poor
5. White: Bad

The resazurin test may be a valuable time saving tool if properly conducted and intelligently interpreted, but should be supplemented by microscopic examination.