When manufacturing IM-food, it is important to control
the water content because water activity is closely related to
water content (Leistner, 1987). In this study, the water
activity of semi-dried jerky was within the range of 0.82–
0.88 (Table 3). There were no clear differences among the
various pork/beef levels with related to water activity
(P > 0.05). However the water activity of jerky prepared
with cellulose casings was lower than jerky prepared with
other casings (P < 0.05). Water activity is useful to describe
the thermodynamic equilibrium state of jerky (Labuza,
1980; Rockland & Nishi, 1980), and foods such as jerky
must have a stable water activity to avoid changes in quality
during storage (Yamaguchi, Naito, Okada, & Nagase,
1986). Thus, the manufacturing process has an important
effect on the water activity and, hence, the quality of the
product during storage.