( ( ( The ( chemical energy ) ) ( of foods ) ) ( ( ( is ( most often ) ) ( expressed ( in ( units ( of ( ( ( calories or ) kilocalories ) ( -LRB- ( kcal -RRB- ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (JJ chemical) (NN energy)) (PP (IN of) (NP (NNS foods)))) (VP (VBZ is) (ADVP (RBS most) (RB often)) (VP (VBN expressed) (PP (IN in) (NP (NP (NNS units)) (PP (IN of) (NP (NP (NNS calories) (CC or) (NNS kilocalories)) (PRN (-LRB- -LRB-) (ADJP (JJ kcal)) (-RRB- -RRB-)))))))) (. .)))
The chemical energy of foods is most often expressed in units of calories or kilocalories (kcal).
(ROOT (S (NP (DT A) (NN calorie)) (VP (VBZ is) (VP (VBN used) (S (VP (TO to) (VP (VB express) (NP (NP (DT the) (NN amount)) (PP (IN of) (NP (NN energy)))) (PP (IN in) (NP (NN food)))))))) (. .)))
A calorie is used to express the amount of energy in food.