THERMAL ANALYSES OF SOME PEPPERS AND SPICES WITH DIFFERENTIAL SCANNING CALORIMETRY

ABSTRACT Herbal products obtained by grinding the roots, leaves, fruits, seeds, buds, flowers, and bark of plants that give smell and taste and have an appetizing feature are called spices. The use and trade of spices date to the first centuries. Even in the oldest known civilizations, it is included in historical tablets where spices are used in food, to prevent the deterioration of some foods, and to make medicines and ointments. Spices have many beneficial effects on health such as positive effects on lipid metabolism, anti-diabetic, antioxidant, antiinflammatory, and digestive properties. However, it has gained a great place in our kitchens to give a good appearance, taste, flavor, and aroma to the food. Today, many kinds of spices are easily accessible, and their mixtures are prepared and used. An increase in the number of microorganisms and the formation of pathogens occur in spice products that are grown, harvested, and stored under inappropriate conditions. These conditions and some characteristics of spices can be investigated by using Differential Scanning Calorimetry (DSC). Glassy transition temperature (Tg) is one of these characteristics and it houses much information about the thermodynamical, physical, mechanical, and electrical properties of a matter [1]. Additionally, it gives us information regarding the sample’s storage temperatures [2]. In this research, Tg values of 27 different spices which is collected from Spice Bazaar-Istanbul were determined by DSC (The data of only 5 of them has been added to the summary here). To perform analyses, 10 mg of each species are weighted and measured with 10 ºC/min heating rate under a nitrogen atmosphere with a flow rate of 30 ml/min (Shimadzu, DSC 60Plus). All the spices were stored at room temperature during the research. According to DSC thermograms (Figure 1), black pepper in powder form has the lowest Tg value which is 47.20 ºC among other spices. It is followed by cinnamon with Tg value of 49.36 ºC, Curry with Tg value of 49.64 ºC, and Thyme with Tg value of 65.67 ºC. Chili pepper has the highest Tg value which is 66.51 ºC. Storage temperatures must be lower than Tg values of the sample to preserve the chemical bonds between the molecules. Additionally, Tg values have the information about composition density of the samples [3]. After all the conditions considered, it can be concluded that Chili pepper has denser and more stable composition than black pepper, thyme, cinnamon, and curry.Keywords: Pepper, Thyme, Cinnamon, Curry, DSC, Glassy Transition Temparatur