Ensure safe probiotic-rich fermented foods with Indigo® residual QAC test strips; verify quaternary ammonium sanitizer residues at ≤100 ppm (detectable down to 10 ppm) to protect cultures, prevent off-flavors, and reduce allergy risks. Meet HACCP, FSMA, and export standards for dairy, soy, kombucha, pickled vegetables, and other fermented products.
Fermented foods such as yogurt, kefir, kimchi, sauerkraut, miso, and kombucha depend on carefully balanced microbial cultures that provide both flavor and probiotic health benefits. Sanitizing food-contact surfaces with quaternary ammonium compounds (QACs, or quats) helps prevent contamination and allergen cross-contact, but residual levels must remain ≤100 ppm to avoid harming beneficial probiotics or leaving unsafe residues. Indigo® residual quat test strips (0–100 ppm, sensitive down to 10 ppm) provide quick, reliable verification that sanitizer residues comply with HACCP, FSMA, and CFIA standards while preserving the probiotic viability that defines fermented foods.
Verify low residues: Confirm surfaces are ≤100 ppm with Indigo® strips, detecting down to 10 ppm.
Protect probiotics: Test rinses before fermentation to avoid suppressing starter cultures.
Prevent allergen cross-contact: Clean and test equipment used for soy, dairy, and gluten-based fermentations.
Document compliance: Maintain sanitizer logs for FSMA, HACCP, and organic audits.
Preserve flavor & texture: Ensure sanitizer residues do not carry over into brines or fermenting vessels, preventing bitterness or off-notes.
Support clean-label claims: Demonstrate proactive residue testing to reassure consumers seeking probiotic integrity and natural processing.
The directions on the test strip bottle are for testing liquid quat solutions. Test surfaces for residues by first wetting the strip's testing pad with water (deionized or distilled if available). Then press against fruits, vegetables, cutting boards, utensils, etc. for at least 10 seconds & then compare against the color chart.
Levels less than "10" ppm are impossible to determine but some organic certifications call for "0" ppm. This is because water alone causes a reading of 10ppm. Read more in our blog on What 10ppm really means? when measured on surfaces of knives, cutting boards, fruits or vegetables.
Related information or images
Residual Quat 10-100 ppm
Berries
Dairy-Cheese
Grains-Nuts
Leafy Greens
Microgreens-Sprouts
Wild Organic Rice
Specifications
Swish strip in liquid 5 times & then compare to color chart after 10 seconds.
Read ≤10-30-60-80-100ppm ppm for quaternary ammonium disinfectant concentration.
Indigo® quat test strips have a guaranteed minimum 3 year shelf life but desiccant lined vials allow for 5+ years.
Store at 20-30C, in a dry place out of direct sunlight.
Indigo® QAC test strips are calibrated for Oasis 146, see details.
Consult your supplier if any special testing is necessary for their formulation.
Solution temperatures from ~30-45C can cause strips to read up to ½ unit a chart unit higher.
Temperatures above 45C can shift the results 1 chart unit higher. Testing at room temperature
Hard water (above 500 ppm) can cause the strips to read high by up to 1 chart unit.
The number of strips (100) per vial is approximate.
