Evaluation of rheological properties and quality of xylitol-substituted dadih
Dadih is a dairy based dessert made of milk, water, sugar, and agar that is popular especially among South East Asian people. It has sweet taste due to high sugar content in its formulation. An excessive sugar intake is harmful to human health, and it would be beneficial if conventional sugar...
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| Format: | Thesis |
| Language: | English |
| Published: |
2015
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/67710/1/FK%202015%20118%20IR.pdf |
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| Summary: | Dadih is a dairy based dessert made of milk, water, sugar, and agar that is popular
especially among South East Asian people. It has sweet taste due to high sugar content
in its formulation. An excessive sugar intake is harmful to human health, and it would
be beneficial if conventional sugar is replaced by a sugar substitute. In order to produce
a healthier dadih, xylitol that has less energy and possesses sweetening power
comparable to sucrose, was used as sugar substitute. To produce a new product such as
xylitol substituted dadih, it is crucial to evaluate the suitable range of process
parameters with various xylitol compositions in properties and quality. In this study,
the evaluated properties were in terms of mechanical (rheological and texture) and
thermal properties. Safety (total plate count and water activity) and sensory analysis
were measured to evaluate the dadih quality.
Thus, the first section of this current research was to investigate the effects of process
conditions and xylitol concentrations in term of rheological and textural properties of
dadih. Process conditions set up were cooking temperatures (85-95˚C) and cooking
times (10-20 minutes) while the xylitol set up were at three levels of compositions (0%,
50%, and 100%). It was found that cooking temperature had the biggest impact on
rheological and textural properties of dadih. All dadih samples showed an elastic
characteristic (n’<1) with gel-like behavior where value of G’ (storage modulus) was
higher than G” (loss modulus). In general, the presence of xylitol in dadih contributed
to softer texture compared to product that is made from sucrose. Thus, xylitol
substituted dadih prepared at 85C with cooking time 15 and 20 minutes have met the
required texture in term of hardness and internal gel strength as the conventional dadih.
The second section of this study focused on thermal and safety analysis of dadih
prepared at temperature 85˚C with two points of cooking time (15 and 20 minutes). At
both cooking time (15 or 20 minutes) as xylitol substitution increase, the onset
temperature and enthalpy values were decreased, indicating a weaker structure of dadih
with xylitol compared to sucrose. Dadih that was prepared with total xylitol (100%)
exhibited the lowest onset temperature To (97.71±0.4˚C for 15 minutes and
99.85±0.18˚C for 20 minutes) and enthalpy values (2096.98±1.4 Jg-1 for 15 minutes
and 2422.61±3.6 Jg-1 for 20 minutes). Dadih samples that demonstrated low values of
onset temperature and melting enthalpy indicated that less energy was required to
change the structure.Safety analysis was done to predict the stability and product quality of xylitol
substituted dadih by evaluating microbial growth throughout the storage period of 25
days. From total plate count (TPC) and water activity analysis, all samples was totally
spoiled at Day 25 where it contained >300 organism per gram and achieved maximum
water activity value, aw (1). Spoilage of dadih with 100% xylitol was slightly
prolonged, which was completely spoiled at Day 24 and 25, for 15 and 20 minutes
cooking time respectively. However, dadih samples with total sucrose (0%) were
observed to be spoiled earlier compared to the former, which was on Day 23. Extended
shelf life and stability of dadih substituted xylitol might be due to natural
characteristics of xylitol of having low water activity.
Last section of this research was to evaluate the sensory analysis of the dadih. Based on
eight attributes of sensory analysis, dadih that was prepared at 15 minutes cooking time
for both total sucrose (0%) and xylitol (100%) was more preferable compared to
samples 20 minutes cooking time. However, there were no significant differences (p >
0.05) for overall acceptability of both samples with 0% and 100% xylitol prepared at
15 minutes cooking time. Based on sensory evaluation, the score for dadih with xylitol
substitute was above ‘slight like’, which indicated a promising future to conventionally
produce xylitol substitute dadih. Therefore, the outcome of this study has shown that
xylitol is potentially to be utilize as sugar substitute for dadih production. |
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