Qualitative Analysis of Formalin Content in White Tofu at Traditional Markets in Surakarta / Analisis Kualitatif Kandungan Formalin pada Tahu Putih di Pasar Tradisional Surakarta

Background: Formalin is still frequently misused as a preservative in white tofu despite being prohibited in food products due to its toxic, irritant, and carcinogenic properties. Therefore, monitoring its presence in traditional markets requires detection methods that are simple, accurate, and well validated. Objective: This study aimed to detect formalin in white tofu sold in traditional markets in Surakarta City and to compare and validate three qualitative formalin detection methods (Nash reagent, KMnO₄, and Schiff reagent) in combination with Thin Layer Chromatography (TLC). Methods: A total of 10 white tofu samples were randomly collected from five traditional markets in Surakarta. The samples were extracted and analyzed using colorimetric tests with Nash, KMnO₄, and Schiff reagents, followed by confirmatory analysis using TLC. Method validation included determination of the limit of detection (LOD) and specificity. Results: Formalin was detected in 30% of the samples (B1, C1, and D2) by all applied methods, while the remaining 70% showed negative results. The LOD test indicated that the Nash reagent exhibited the highest sensitivity, detecting formalin at concentrations as low as 3.125 ppm, followed by TLC (6.25 ppm), Schiff reagent (25 ppm), and KMnO₄ (50 ppm). All methods demonstrated good specificity, with no false-positive results observed in blank samples and negative controls. Conclusion: This study confirms the misuse of formalin in 30% of white tofu samples from traditional markets in Surakarta. The Nash reagent is recommended as the most sensitive method for initial screening, while TLC serves as an effective confirmatory method. The combination of Nash reagent and TLC provides a simple, sensitive, and specific approach for formalin surveillance in white tofu at the field level.

Latar Belakang: Formalin masih sering disalahgunakan sebagai pengawet tahu putih meskipun dilarang penggunaannya dalam pangan karena bersifat toksik, iritatif, dan karsinogenik. Oleh karena itu, pemantauan keberadaannya di pasar tradisional memerlukan metode deteksi yang sederhana, akurat, dan tervalidasi. Tujuan: Penelitian ini bertujuan untuk mendeteksi kandungan formalin pada tahu putih yang dijual di pasar tradisional Kota Surakarta serta membandingkan dan memvalidasi tiga metode uji kualitatif formalin (reagen Nash, KMnO₄, dan Schiff) yang dikombinasikan dengan Kromatografi Lapis Tipis (KLT). Metode: Sebanyak 10 sampel tahu putih diambil secara acak dari lima pasar tradisional di Surakarta. Sampel diekstraksi dan dianalisis menggunakan uji warna reagen Nash, KMnO₄, dan Schiff, serta analisis konfirmasi dengan KLT. Validasi metode meliputi pengujian batas deteksi (LOD) dan spesifisitas. Hasil: Sebanyak 30% sampel (B1, C1, dan D2) terdeteksi positif mengandung formalin oleh seluruh metode uji, sedangkan 70% sampel lainnya menunjukkan hasil negatif. Uji LOD menunjukkan bahwa reagen Nash memiliki sensitivitas tertinggi dengan kemampuan mendeteksi formalin hingga 3,125 ppm, diikuti KLT (6,25 ppm), Schiff (25 ppm), dan KMnO₄ (50 ppm). Seluruh metode menunjukkan spesifisitas yang baik tanpa adanya hasil positif palsu pada sampel blanko dan kontrol negatif. Kesimpulan: Penelitian ini mengonfirmasi adanya penyalahgunaan formalin pada 30% sampel tahu putih di pasar tradisional Surakarta. Reagen Nash direkomendasikan sebagai metode skrining awal yang paling sensitif, sementara KLT efektif digunakan sebagai metode konfirmasi. Kombinasi keduanya merupakan pendekatan yang sederhana, sensitif, dan spesifik untuk pengawasan formalin pada tahu putih di lapangan.