Determination of moisture in powder and lyophilised saffron (Crocussativus L.) by Karl Fischer method

Saffron is a spice obtained from the dried stigmas of the purple-flowered saffron crocus (Crocus sativus L.). The determination of the water content in saffron is very important in order to establish its microbiological stability and consequently to determine the commercial value. The average moisture content in dried saffron powder ranges between 10-12% causing a slow degradation of the product. On the other hand lyophilised saffron has lower water content and a better stability. The reference method commonly used for the determination of moisture in saffron it is based on the gravimetric loss of weight after heating at 105 °C for 16 hours. In this paper a procedure to obtain lyophilised saffron is proposed and two different methods, namely the infrared balance and the Karl Fischer titration, are used to determine moisture in dried and lyophilised saffron powder, and results are compared with the reference method. The Karl Fischer method, never applied so far to determine moisture in saffron, gave the best results. The average values determined were 6.87% and 4.01% (w/w) for conventionally dried and lyophilised saffron powder, respectively. The Karl Fischer titration method allows to determine in a faster manner the moisture in saffron powder and in lyophilised saffron, without any interference and using a minor quantity of saffron compared to the gravimetric procedure reported in the reference method. The volatile matter content, differently from the reference method, this way is not determined.