**2. Thermal food processing and its effects on food phenolic compounds**

Majority of plant foods are thermally processed into their ready-to-eat and stable forms. Notable examples of thermal processing techniques include roasting, microwaving, boiling, steaming and drying. However, research has demonstrated changes in food bioactive compositions such as phenolics during thermal processing. For instance, boiled broccoli showed reduced concentrations of caffeic acid (2.2 mg/100 g), quercetin (10 mg/100 g) and antioxidant capacity compared to their raw forms (caffeic aicd-6.6 mg/100 g and quercetin – 23.5 mg/100 g) [7]. Similarly, roasted coffee beans showed reduced phenolic levels and antioxidant capacity. These changes were attributed to oxidation by the triggering of nonenzymatic trans-glycosylation of phenolics into melanoidin as a result of Maillard reaction. Additionally, oxidation of phenolic compounds into their less bioactive forms such as quinones, and (−)-catechin into (+)-catechin has been reported as a result of thermal processes such as roasting [8]. Due to these bioactive reductions,

*Novel Non-Thermal Processing Technologies: Impact on Food Phenolic Compounds... DOI: http://dx.doi.org/10.5772/intechopen.98688*

there is a collective effort by researchers to develop non or medium thermal techniques that can help enhance/maintain phenolic levels along food processing.
