Determination of malic acid in the coffee production chain
By analyzing L-Malic acid and L-Lactic acid, it is possible to assess the correct progress of the malolactic fermentation. L-Malic acid is also an important quality parameter for green and roasted coffee.
Analyzing Malic Acid in Coffee: Why It Matters
The analysis carried out in the fermentation phase allow to control this delicate process and can be applied to the various types (natural, washed, honey, anaerobic, ...). They have the purpose of determining the right timing of the fermentation process and can give important indications to produce a coffee with the desired characteristics.
The analysis carried out on green coffee allow to assess the quality of the product, to evaluate its organoleptic potential and its chemical characteristics. This will allow making the right choices in the following roasting phase and evaluating its conservation over time.
The analysis carried out on the roasted coffee are proper to identify the chemical and organoleptic characteristics of the product and to give a first evaluation of the sensory profile that could be found in the cup. The same analysis can also be carried out on the extracted coffee in order to evaluate the efficiency of the extraction process.
Method
Test type: End Point.
Time testing: 4 minutes.
Analysis sessions with multiple samples are possible up to a maximum of 16 tests for CDR CoffeeLab®.
Sample treatment
Fermentation: The analysis can be done on pulp or fermentation liquid.
The liquid part must be extracted from the pulp with an extraction system (Food Press) and then centrifuged. The fermentation liquid must be centrifuged
Green coffee beans (without parchment) must be finely ground and sieved to obtain a homogeneous powder. Weigh 1 gram of coffee powder into a centrifuge tube and add 5 ml of distilled water. Mix for about 10 minutes and then let it settle for about 10 minutes. Take 1 ml of supernatant and add it to the tube containing the bleaching powder. Keep mixing for 10 minutes and then centrifuge for 10 minutes at 12000 rpm.
Roasted coffee: the beans must be ground to fine grind and the powder must be as homogeneous as possible.Weigh 1 gram of coffee powder into a centrifuge tube and add 5 ml of distilled water. Mix for about 10 minutes and then centrifuge for 5 minutes at 5000 rpm. Take 1 ml of supernatant and add it to the tube containing the bleaching powder. Keep mixing for 10 minutes and then centrifuge for 10 minutes at 12000 rpm.
Extracted coffee: Take 1 ml of sample and add it to the tube containing the bleaching powder. Keep mixing for 10 minutes and then centrifuge for 10 minutes at 12000 rpm.
Test Principle
L-Malic acid is oxidized in an alkaline environment through an enzymatic reaction and converted into oxaloacetic acid, which is turn produces NADH. The increase of absorbance, measured at 366 nm (end-point), is directly proportional to the concentration of L-Malic acid in the sample.
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Reagent test Kits
Measuring range
| Analyses | Measuring range | Resolution | Repeatability |
|---|---|---|---|
| L-Malic acid | 0.2 - 10 g/Kg | 0.01 g/Kg | 0.33 g/Kg |
| L-Malic acid espresso | 0.05 - 5 g/L | 0.01 g/L | 0.08 g/L |
| L-Malic acid fermentation liquid | 0.1 - 10 g/L | 0.01 g/L | 0.08 g/L |
| L-Malic acid Pulp | 0.1 - 10 g/Kg | 0.01 g/Kg | 0.08 g/Kg |
CDR CoffeeLab® the analysis equipment for the world of coffee from origins to roasting
CDR CoffeeLab®
- Complete analysis panel, supplied already configured
- Up to 16 determinations simultaneously
- Possibility of carrying out analyses of the same sample
- Integrated printer
- Full connections (LAN - USB - Bluetooth barcode/QR code reader)