Electromagnetic Radiation-Based Dry Blanching of Red Bell Peppers: A Comparative Study.

Retention of water-soluble nutrients, prevention of solid loss and elimination of
waste water generation are some of the advantages of dry blanching. Dry blanching
of red bell pepper (Capsicum annuum L.) slices using infrared (IR) and microwave
(MW) radiations was attempted and its performance was compared with
conventional water and steam blanching methods. Processing conditions (time
and temperature) were standardized on the basis of degree of enzyme inactivation
(peroxidase, polyphenol oxidase). Effect of blanching methods on retention of
micronutrients such as ascorbic acid, β-carotene and protein, besides product
shrinkage, structure and texture (shearing force) were analyzed. Water and steam
blanching were found to need lower processing time (1.0 and 1.5 min, respectively)
compared with IR (6.0 min) and MW blanching (3.0 min). However,
MW-blanched samples retained higher amounts of ascorbic acid (94.7%). Dry
blanching with IR (150C) and MW (17.5 W/g) resulted in higher retention of
β-carotene (103.2 and 118.6%, respectively) compared with water (60.3%) and
steam blanching (88.3%). Dry blanching resulted in moisture loss (1–6%) and
shrinkage, perhaps resulting in higher shearing force observed in dry blanched
slices. Scanning electron micrographs indicated that method of blanching has a
role on extent of effect on cell structure.
PRACTICAL APPLICATIONS
Red bell pepper is a rich source of ascorbic acid and β-carotene. This study
explored the possibilities of dry blanching red bell pepper using infrared and
microwave radiation as a potential alternative to water and steam blanching. The
dry blanching is expected to retain higher amount of nutrients, reduce solid loss
and eliminate effluent generation besides being convenient to operate.