| Summary: | Osmotic dehydration (OD) is an effective preservation technique to remove water
from fruits and produce high quality products with minimal nutrients loss. Sorbitol is
a low-glycemic carbohydrate with complementary sugar’s functionality with lower
glycemic index compared to sucrose. The osmotic dehydration kinetic and microbial
stability of the osmodehydrated pineapple of sorbitol-sucrose mixtures during
storage were determined in this study. OD were conducted using 65 °Brix sucrosesorbitol
mixture ranging from 0 to 100 % concentration at 40 °C for 240 minutes and
subjected to hot air drying at 50 °C to approximately 30 % moisture content.
Samples were vacuum-packed and stored at 4 °C for storage study. Textural,
moisture content, aw, pH, colour, flavonoids, vitamin C and bromelain were
determined using texture analyzer, moisture analyzer, water activity meter, pH meter,
Hunter LAB calorimeter, spectrophotometer, standard Vitamin C AOAC 967.21 and
casein digestion unit (CDU) method, respectively. The results showed that in general
all formulations studied gave decreasing trend for weight reduction (WR) and water
loss (WL) and increasing trend for solutes gain (SG). Sorbitol substitution at 75 %
and 100 % were recommended for osmodehydrated pineapple because both
formulations gave the lowest WR, highest WL and SG values, which fulfilled the
requirement as a high quality osmodehydrated fruits. In addition, both formulations
had the lowest water activity, low pH values, medium firmness and no obvious
browning. Results on microbial stability showed that osmodehydrated pineapple
with sorbitol can be stored at 4ºC for more than 2 months at bacteria count < 106
CFU/g and yeast and mould ≤ 104 CFU/g. However, there were no significant effects
of different osmotic solutions used on the retention of vitamin C content and total
flavonoid content because all showed degradation throughout storage and firmness
of osmodehydrated pineapple decreased with storage. However, for bromelain
activity, sorbitol treated pineapple is significant in retaining the bromelain activity.
In conclusion, sorbitol treated osmodehydrated pineapple have a better extended
shelf life and better retention of bromelain activity which showed that sorbitol can be
used as an alternative osmotic solution in osmotic dehydration of pineapple.
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