Analysis of internal browning of roasted hazelnuts

Formation of internal browning in hazelnuts during roasting and effect of w ater activity on internal browning were studied. Water activity significant ly affected color attributes of roasted hazelnuts. As the water activity in creased internal browning also increased. Over the water activity range of study (0.29-0.83), water activity of 0.29 was found to be the least suscept ible to internal browning. Roasted samples, having dark-coloured internals contained significantly more total sugar and sucrose than roasted samples, having light coloured internals. Brown centres contained more total sugar a nd sucrose than light-coloured outer layers. Inner layers of raw hazelnuts contained about 50% more total sugar and sucrose than light-coloured outer layers. Polyphenoloxidase activity could not be detected in the sample roas ted at 130 degreesC for 16 and 30 min. These results indicated that interna l browning during roasting was due to localised concentration of reactants and, subsequently, the higher non-enzymatic browning reaction rate in the c entre of hazelnuts. (C) 2001 Published by Elsevier Science Ltd.