2.3 Modulated differential scanning calorimeter (MDSC)
The MDSCTM uses both the linear heating rate as well as a modulated (sinusoidal) heating rate to determine the total heat flow rate, see Eq. 1. The linear heating rate provides information on the total heat rate while the sinusoidal heating rate provides the heat capacity information from a fraction of the heat flow [27].
\begin{equation} \frac{\text{dQ}}{\text{dt}}=C_{P}\beta+f\left(T,\ t\right)\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ (1)\nonumber \\ \end{equation}
Where \(\frac{(dQ}{dt)}\) is the total heat flow due to the linear heating rate (equivalent of standard DSC), \(C_{P}\) is the heat capacity component calculated from the heat flow due to the sinusoidal heating rate, \(\beta\) is the linear heating rate of the sample,\(C_{P}\beta\) is the reversing heat flow while \(f(T,\ t)\) is the kinetic component of total heat flow known as the non-reversing heat flow which can be calculated from the difference between the reversing heat flow and total heat signal component.
In this study, a Discovery DSC® (TA Instruments, Inc. New Castle, DE, USA) equipped with a modulated Differential Scanning Calorimeter (MDSCTM) software using a Liquid Nitrogen Cooling Accessory (LNCA) at atmospheric pressure was used for all measurements. Helium gas at a flow rate of 50 mL/min was purged through the MDSCTM. The MDSCTM equilibrated at a temperature of -150 ˚C and measurements were performed at an underlying heating rate of 3 K/min up to a temperature of 100 ˚C; amplitude of modulation 1 K and period of 60 s for the sample mass of 2 mg – dry biomass weight. Temperature and heat capacity calibrations were performed with a MDSCTM certified Indium reference material (Part No. 915061.901) and a sapphire for the specific heat capacity determinations (Part No. 9703790.901), respectively at similar operating conditions as used for the samples. The data were analysed using a TRIOS software v4.1.1.33073 (TA Instruments Inc. USA). All procedures were done in triplicate. All dataset are openly available in [28].