The food value of the snack bar could be calculated by
Food Value = CcalΔT/m
So, the food value for the snackbar would be
Food value = (6.15 kJ/°C)(1.37°C)/0.721 g = 11.68 kJ/g
Convert kJ to cal (1 kJ = 239 cal)
Food value = 11.68*239 = 2791.52 cal/g