Effect of processing methods and storage environment on moisture adsorption characteristics of ginger (Zingiber Officianale)

Abstract

The objective of this study was to determine the effect of processing methods and storage parameters on moisture adsorption characteristics of dry matured yellow ginger (Zingiber officianale) to provide information for the prediction of shelf life and selection of packaging materials. Moisture adsorption was determined gravimetrically. Saturated solutions of sulphuric acid were prepared to provide constant relative humidity environments. The experimental design was split plot comprising six processing methods (peeled-blanched ginger slice, peeled ginger slice, unpeeled-blanched ginger slice, unpeeled ginger slice, peeled ginger flour and unpeeled ginger flour), four storage temperatures (20, 30, 40 and 50ºC) and six levels of relative humidity in the range of 3.71 – 93.9% which represents some of the environmental conditions that ginger products are exposed to in practice. There was a highly significant processing methods, temperature and water activity effects on the equilibrium moisture content (EMC). For all the processing methods and at all temperature levels, EMC increased with increase in water activity at constant temperature. At constant water activity levels, EMC decreased with increase in temperature. The EMCs of the peeled ginger slices and flours were generally lower than those of the unpeeled ginger at the temperatures and water activities studied. The
EMCs of peeled ginger flour were generally higher than the peeled ginger slices at all the temperatures and water activities studied. At any given storage temperature and relative humidity, unpeeled ginger samples were more hygroscopic than the peeled. Also at the temperatures and relative humidities studied, ginger powders absorbed more moisture than the slices. The EMCs of blanched ginger were consistently lower than the unblanched. This implies that blanched ginger has decreased tendency to
absorb moisture in storage. Therefore on the basis of shelf stability, Peeled-Blanched Ginger Slice (PBS) is recommended followed by Peeled Ginger Slice (PGS) and Unpeeled-Blanched Ginger Slices (UBS) in that order. The Unpeeled Ginger Slice (UGS), Peeled Ginger Flour (PGF) and Unpeeled Ginger Flour (UGF) did poorly and therefore not recommended.