| Author | Siriwan Tungsangprateep |
| Call Number | AIT Diss. no.PH-04-03 |
| Subject(s) | French fries--Quality
French fries--Storage
|
| Note | A dissertation submitted in partial fulfillment of the requirements for the
degree of Doctor of Technical Science, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. PH-04-03 |
| Abstract | Fried cassava-shrimp chips (Khao Kriap) are popular as snack foods in Thailand
and other Southeast Asian countries. They are prepared traditionally by gelatinizing the
dough formed from a mixture of tapioca flour, water, spices and other nutritional
ingredients such as fish, shrimp or vegetables. Moisture gain by the chips during storage
may destroy the crisp texture and lead to rejection by consumers. In addition, the
presence of oxygen may promote the oxidation of oils absorbed during frying resulting in
rancid off-flavor.
The overall objective of this study was to investigate the factors affecting the
quality of fried cassava-shrimp chips during storage in various types of flexible packages.
Preliminary tests showed that commercially available chips (Manora® brand) could be
used in experimental work due to their similarity with the indigenously produced cassavashrimp chips with regard to moisture content, oil absorption during frying, volumetric
expansion ratio, linear expansion and preference scores based on a nine-point Hedonic
scale.
Equilibrium moisture sorption isotherms of fried cassava-shrimp chips were
investigated by measuring water activity (aw) at 20, 30 and 40°C for modeling transient
diffusion of moisture. The sorption isotherms followed a type III shape in the aw range of
0.1 to 0.9 showing negligible influence of temperature, and were best represented by the
GAB, modified Henderson and Henderson equations. Effective moisture diffusivity of
chips based on analytical solution of Fick's law ranged from 0.8x10- 11 to 2.1x10- 10
m
2
/s
during exposure to fixed relative humidity (50, 70 and 90%) and temperature (20, 30 and
40°C) environments. An Arrhenius type relationship adequately described the
dependence of effective moisture diffusivity both on temperature and relative humidity
and led to good agreement between experimental and estimated transient moisture
sorption data.
The changes in the quality of fried cassava-shrimp chips in flexible packages
made from three different types of laminated films: 1) NY15/PE20/LLDPE100 (coded
NYPE); 2) OPP HS30/DL/LL-HD-LL85 (coded PPPE); and 3) PET13/PE18/CPP20
(coded PETPE) were investigated during storage in 50, 70 and 90% relative humidity
(RH) environments at 30°C in terms of physico-chemical parameters and sensory
attributes. The chips packed in metal cans served as control. It was found that the loss of
crispness in chips during storage mainly depended on the increase in moisture content,
and thus lowered the sensory quality in all cases. The film permeability and external RH
were found to be the major factors affecting moisture gain by the chips during storage.
The changes in the moisture content of chips with time were modeled based on Fick's law
and Henry's equation using parameters determined from GAB moisture adsorption
isotherm at 30°C. The predicted moisture contents of chips durin~ storage in three flexible
packages showed good agreement with experimental data (R >0.8) when using both
linear and original isotherms. A critical moisture content of about 4.7% db was
established for estimating the shelf-life of chips using graphical method. The good
agreement between estimated and experimental moisture gains in chips during storage
apparently led to reliable estimates of the shelf-life as well. The shelf-life of chips packed
in PETPE, NYPE and PPPE coded films were determined in respective ranges of 8-19,
22-50 and 35-74 days for storage experiments carried out at RH ranging from 50 to 90%.
lll
The NYPE film, which had lowest oxygen transmission rate and resulted in
medium shelf-life for the packaged chips, was selected for validating the moisture
transfer model and investigating the effects of moisture absorbing (MA) or oxygen
absorbing (OA) sachets on the shelf-life of chips. The changes in quality and stability of
chips were evaluated during storage at 30°C and fixed RH of 50, 70 and 90%. The chips
stored in metal cans with an OA sachet were used as control. The predicted moisture gain
by chips and their shelf-life under different storage conditions were in good agreement
with the experimental data (R2
>0.8). The presence of OA sachet helped in rapid reduction
of oxygen in the head space of packages from about 20.9% to less than 0.5% within 3
days. The low oxygen levels in packages were maintained during the subsequent storage
without being significantly affected by the moisture increase in chips. Similarly, the rate
of moisture gain in packed chips with MA sachet was observed to be about two-third of
the rate without MA, and resulted in about 50% increase in shelf-life. |
| Year | 2004 |
| Corresponding Series Added Entry | Asian Institute of Technology.|tDissertation ; no. PH-04-03 |
| Type | Dissertation |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Food, Agriculture and Natural Resources (Former title: Department of Food Agriculture, and BioResources (DFAB)) |
| Academic Program/FoS | Postharvest and Food Process Engineering (PH) |
| Chairperson(s) | Jindal, Vinod K.; |
| Examination Committee(s) | Athapol Noomhorm;Rakshit, Sudip Kumar;Kumar, S.; |
| Scholarship Donor(s) | Royal Thai Government; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2004 |
