Comparison of the effects of vacuum oven-, freeze-, solar-, and microwave-drying with traditional drying methods on the qualitative characteristics of ghaen saffron

Saffron, the world’s most expensive condiment, is one of Iran’s most important non-petroleum exports. Its annual production in the country is about 220-228 tons and its export value over 59–70 million USD (the price is 454–482 USD/kilogram). The aim of this study was to compare the effects of different dehydration methods, including vacuum oven-, freeze-, microwave- and solar0drying methods with the traditional drying method on the characteristics of saffron and determine the most suitable method. The study was conducted in the National Nutrition and Food Technology Research Institute, Tehran, Iran between 2001 and 2002. The methodology was experimental. A farm in the safflower-growing region of Ghaen was selected randomly, and the flowers were picked and mixed thoroughly. The percentage yield of the stigmas, and the morphological and chemical (moisture, ash, total nitrogen and acid-insoluble ash) characteristics were determined. Stigmas were dried, followed by determinations of the moisture content, total ash, acid-insoluble ash, cold water-soluble extract, total nitrogen, crude fiber, crocin, picrocrocin, and saffranal. The total microbial, choliform, yeast, mold, and Esherishia coli counts were also measured in the dried samples. The results indicated that from the color (crocin) point of view the solar-, vacuum oven-, and microwave-dried samples were the best (p<0.05). As regards the contents of saffranal and picrocrocin, responsible for aroma and taste, respectively, there were no significant differences among the dried samples. The results of the microbial tests on the dried samples indicated that all the samples except those dried using the traditional or the freeze-drying method, the counts conformed with the Iranian standards. Although all of the four non-traditional methods of drying were better than the traditional method, we recommend sun-drying as a suitable method in the rural areas where saffron is produced.