Abstract:
This study was aimed to prepare tomato sauce using tomato powder produced
by two drying methods; microwave vacuum and conventional drying. Ripen
tomatoes of Thilina variety were washed, blanched for 1 minute by dipping in
hot water at 60 °C and cut into 1 cm thick slices. The slices were dehydrated in
conventional dryer and microwave vacuum dryer, ground and packed in
sterilized, sealed glass bottles and stored in a cool dry place at room
temperature. Tomato sauces were prepared from produced powders according
to the Sri Lanka Standards (SLS) and their qualities were compared with three
branded tomato sauces. Tomato powders and sauces were evaluated for
physiochemical properties (color, pH, brix, titratable acidity, ascorbic acid
content and viscosity), proximate composition, antioxidant properties [total
phenolic content (TPC), total lycopene content and antioxidant activity] and
microbiological qualities (total plate count, yeast and mould count and E. coli
count). Changes in the quality of the powders and sauces were evaluated up to 5
months of storage at room temperature. Sensory evaluation was carried out
using 5 points hedonic scale using 30 untrained panelists. Results of this study
showed that physiochemical properties and proximate composition were
satisfactory for both tomato powders and sauces during the study period.
Lycopene content of sauces prepared from vacuum dried tomato powders (VTP)
and conventional dried tomato powder (CTP) were 147.74±0.99 mg/kg and
125.97±0.57mg/kg, respectively, which were lower compared tothat of branded
sauces (brand 1 - 198.52±0.83 mg/kg). The highest TPC (32.8± 0.82 mg Gallic
Acid Equivalent (GAE)/g) was obtained in the CTP among the powders, whereas,
the highest TPC was obtained in brand 1 (77.66±0.82 mg GAE/g) among the
sauce samples. Ascorbic acid content was higher (135.12±0.08 mg/100 g) in VTP
compared to all the powder and sauce samples studied. Antioxidant activity was
high in CTP (10.01±0.87 mg/mL) among all the tested samples. Better sensory
acceptance was obtained in the sauces prepared from VTP than sauce prepared
from CTP. All samples exhibited good microbial quality for 6 months of the study
period, according to the SLS. Overall results revealed that microwave vacuum
drying method is successful to preserve color and produce tomato powder with
good physiochemical, antioxidant, and proximate properties.
