The modified Hehner's test (MHT) was applied to detect the formalin in experimentally contaminated and collected commercial cheeses and fish. The spectrophotometric method was adapted to determine the formalin in cheeses and fish samples. The principle of test modification was a complete homogenization and dilution of the examined cheeses and fish samples. By two methods, the incidences of formalin in the market soft and Ras cheeses samples were 31.66 and 3.33%, respectively. Formalin was not detected in the examined market fish samples by MHT, and its concentration by the spectrophotometric method was less than 1 µg/g. The findings of the study indicated that the results obtained by both MHT and spectrophotometric methods were comparable. The applicability of the MHT in different food matrices might mean it has potential as a standard technique with high sensitivity up to 0.001%.

Graphical abstract

(A): Prepared Ras cheese homogenate; (B): Positive and negative modified Hehner's test in the examined Ras cheese samples with different formalin concentrations; (C): Positive and negative modified Hehner's test in the examined soft cheese samples with different formalin concentrations; (D): Negative modified Hehner's test in the examined fish flesh samples with 0.001% formalin concentration; (E): Positive modified Hehner's test in the examined fish flesh samples with 0.1% formalin concentration; (F): Positive modified Hehner's test in the examined fish wash samples with 0.01% formalin concentration

中文翻译：

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改良的 Hehner 检验在奶酪和鱼类中福尔马林检测中的新应用

改进的 Hehner 测试 (MHT) 用于检测实验性污染和收集的商业奶酪和鱼中的福尔马林。分光光度法适用于测定奶酪和鱼样品中的福尔马林。测试修改的原则是对所检查的奶酪和鱼样品进行完全均质和稀释。通过两种方法，市场软奶酪和Ras奶酪样品中福尔马林的发生率分别为31.66%和3.33%。经MHT检测的市售鱼样品中未检出福尔马林，分光光度法检测其浓度小于1微克/克。研究结果表明，通过 MHT 和分光光度法获得的结果具有可比性。

图形概要

(A)：制备的Ras奶酪匀浆；(B)：在不同福尔马林浓度下检验的 Ras 奶酪样品中的阳性和阴性改良 Hehner 试验；(C): 不同福尔马林浓度的软干酪样品中改良 Hehner 试验的阳性和阴性结果；(D)：在含有 0.001% 福尔马林浓度的受检鱼肉样品中，改良 Hehner 试验呈阴性；(E)：在含有 0.1% 福尔马林浓度的受检鱼肉样品中进行阳性改良 Hehner 试验；(F)：在含有 0.01% 福尔马林浓度的检查鱼洗样品中的阳性改良 Hehner 试验