88E-17 |
The effect of microwave heat treatment of apple mash on juice yield and quality |
K. A. GERARD and J. S. Roberts. Dept. of Food Science & Technology, Cornell Univ., W. North St., NYSAES, Geneva, NY 14456 Recent studies suggest that the phytochemicals (including phenolic compounds) widely present in fruits and vegetables provide the antioxidant activity necessary to quench reactive oxygen species which have been implicated in tumor and cancer cell growth. Fresh apples have a high phenolic content and due to their high consumption, contribute greatly to health. Yet up to 99% of the phenolics present in fresh apples can be lost during processing into juice. Heat treatment of fruit mashes has proven effective in increasing the concentration of phenolic compounds in juice, yet current methods remain expensive and produce juice with unacceptable analytical and sensory properties. Microwave energy has the advantage of heating solids rapidly and uniformly. The objective of this research was to evaluate the effect of microwave heating of apple mash on phenolic content, antioxidant activity, sensory quality, inactivation of PPO, and juice yield after hot pressing. McIntosh and Fuji apples were used due to their high phenolic content and antioxidant activity. These apples were mashed and heated in a 2450 MHz microwave oven (1 cubic meter cavity, continuous variable power) to 40, 50, 60, and 70 degrees Celsius before pressing. The juice produced was analyzed for color, Brix, antioxidant activity, and by HPLC for phenolic content. Uniform heating of the apple mash was obtained using 600 W and a cylindrical container with shielding at the edges. Our results demonstrate that the juice produced from pressing heated apple mash was of a high quality with a significant increase in juice yield, phenolic content, and antioxidant activity. Traditional apple juice provides only a fraction of the antioxidant activity of fresh apples. This new process produced an apple juice with increased phenolic content and antioxidant activity, thereby increasing the health benefits and value of this juice.
Session 88E, Fruit & Vegetable Products: Processing
|