33 For this simulation the process was designed to experience 10
destruction of antioxidant properties and physical quality. The example of process calculation is given in Appendix 4. Depending on the graphs, to obtain
commercial sterility product, tempe should be heated on the right side of the red dash line to fullfill a minimum “botulinum cook” F
o
=12x0.21=2.52 min. In addition, canning food industries consider the other heat resistant spores
generally referred to as thermophiles, such as B. stearothermophillus, that have the potential to cause spoilage and economic losses Awuah et al. 2007.
Therefore, to achieve safety quality of the product, tempe has to be subjected to thermal processing in the grey area.
A conventional canning process is commonly conducted at temperature ranging 110-121.1
o
C Hariyadi 2014 for a long time to destroy microorganisms of public health and spoilage concerns. Therefore, it leads to induce permanent
changes to the nutritional and sensory attributes of products. It can be seen from the graphs that heating tempe in the grey region resulted in destruction of textural
and color attributes significantly. However, the antioxidant capacity of tempe can be retained when tempe is heated for short time 11 min in the grey area.
Heating tempe at mild temperature below 100
o
C pasteurization might be alternative process to retain better antioxidant profiles and physical quality of
tempe. This simulation uses C. botulinum type E as target microbe having D
185
=0.28 min and z=16
o
F which is considered to be target pathogen of pasteurized fish and fishery products because this pathogens will survive the
pasteurization process and grow under normal storage conditions FDA 2011, Méndez and Abuín 2006. Furthermore, tempe is identical product to pasteurized
fish both of which are source of protein and has pH 4.5 low acid canned food, LACF and water activity 0.85.
According to FDA 2011, a reduction of six decimal level of C. botulinum type E is suitable 6D process for pasteurization. Because the process is not
severe enough to kill C. botulinum, the pasteurized foods require refrigeration immediately after processing. Consequently the pasteurized products are reduced
oxygen packaged e.g., vacuum packaged or modified atmosphere packaged and have limited shelf life in the distribution chain Ahmed and Shivare 2006.
It can be seen from the graphs that the green dash line performs minimum heating time required to destroy 6 decimal of C. botulinum, thus pasteurized
tempe should be heated on the right side of the green dash line. When tempe is subjected to termal processing at time-temperature combination in this area, the
minimum 10 destruction of antioxidant properties and physical quality in solid and salt solution are achievable. In this case the quality attributes of tempe during
pasteurization can be relatively retained.
Ristanti 2010 has reported that pasteurization process P
185 16
= 37 min could extend the shelf life of tempe untill 25 days in vacuum pacakages of
aluminium foil and stored at 5
o
C. However, this process effectively killed the moulds of tempe but the heat resistant microoganisms was still alive causing
spoilage of the product. Protease from spoilage organisms degraded protein into micromolecules, such as amino acids, ammonia NH
3
, and hydrogen sulfide H
2
S resulting in undesirable appearance and odor of tempe.
34 This research indicated that heating tempe at high temperature
significantly damaged the tempe properties primarily physical quality, thus the process could not retain the freshness of tempe. Canning process might be applied
to preserve and cook the processed tempe that had more softer texture and different visual appearance from the fresh tempe, such as tempe curry, tempe
bacem, tempe steak, etc.
35
5 CONCLUSIONS AND SUGGESTION
5.1 Conclusions
Thermal treatments affected significantly on antioxidant capacity and physical quality of tempe. During heating the rate of change in antioxidant
capacity and physical quality of tempe increased with increase of time and temperature process. The changes of antioxidant capacity had similar trend to total
phenolic content TPC indicating that TPC strongly influenced the antioxidant power of tempe p 0.05, whereas total flavonoid content TFC was relatively
constant during heating. The presence of salt improved solubility pectin which softened the tempe texture. Moreover, the salt solution decreased water activity
that might inhibit the Maillard reaction, thus the visual appearance of fresh tempe was relatively retained.
Not all tested quality attributes could be modeled well as thermal kinetic parameters because some of them were not affected significantly by process
conditions, such as the total flavonoid content, hue, springiness, stickiness, cohesiveness, and chewiness. The heat sensitive quality parameters of tempe
which can be modeled as first-order reaction: antioxidant capacity, TFC, hardness, lightness, yellowness, greenness and chroma.
The activation energy indicated the parameter sensitivity to temperature changes. The slope for degradation of physical properties was sharper than
antioxidant capacity indicating that the rate of physical change was more heat sensitive than other parameter. Determination of activation energy from physical
attributes showed that activation energies for color changes E
a greenness
=181.44 kJmol, E
a yellowness
=82.75 kJmol, E
a chroma
=73.95 kJmol, E
a lightness
=54.98 kJmol were greater than textural changes E
a hardness
=44.32 kJmol. The activation energy for total of antioxidant capacity 14.68 kJmol was smaller than TPC 30.16
kJmol.
5.2 Suggestion
Nutritional attributes of tempe become the attractive factor that affect on buying ability of consumers. Hence, further studies are suggested for analysis
specific compounds that directly affected on antioxidant capacity during thermal processing. Besides, exploration for heat sensitive parameters at broader range of
temperature should be conducted to obtain more accurate kinetic data.
36
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