Judul: Pengaruh Heat Moisture Treatment terhadap Sifat tekstural dan Retrogradasi Gel Pati Aren dan Tapioka
Abstrak: Heat Moisture Treatment (HMT) is one of physical modification techniques that uses limited moisture where heating process at high temperature is implemented for certain period of time. This research studied the effect of HMT modification on textural properties and retrogradation of aren and tapioca starch gel. HMT modification was done by using autoclaving method at 120 oC in 60 minutes for tapioca and 90 minutes for aren. Before autoclaving process, the water content of starch was adjusted into 20% (b/b, wb). The observation of retrogradation was done on starch gel with water content 10% (b/b, db) and refrigerated at 4 oC for 7 days. Textural analysis was done by doing compression using texture analyzer. Degree of retrogradation analysis was done by analyzing the changes of hardness from starch gel, and analyzing amylose hydrolisis using α-amylase enzyme. The result from textural analysis and degree of retrogradation analysis show that HMT modification could make starch gel become fragile, shown by decreasing breaking strain. From degree of retrogradation analysis, it is known that HMT modification increased hardness and degree of retrogradation of starch gel. According to this research, it can be concluded that HMT modification could make starch gel become fragile, increase hardness, and increase retrogradation of native starch gel.
Keyword: textural properties., retrogradation, heat moisture treatment

Judul: Pengaruh Heat Moisture Treatment terhadap Laju Retrogradasi pada Gel Pati Sagu (Metroxylon sp.) dan Pati Aren (Arenga pinnata)
Abstrak: Starch is a carbohydrate reserves that are found in various plants and is the second largest source of carbohydrates after cellulose. One starch derived from palm. As for example of the palm starch sources is sago (Metroxylon sp) and sugar palm (Arenga pinnata). Native starch usually has a limited functional properties for a specific process. Modification of starch is usually done to improve the functional properties of starch for a particular purpose. Physical modification such as heat moisture treatment (HMT) has the potential to increase the functional properties of native starch. The purpose of this research was to study the effects of HMT on the rate of starch retrogradasi through the rate of sineresys, the changing textural properties, water content and water activity (aw) during storage. Modification of HMT performed with the method of autoclaving at a temperature of 60 minutes 120oC to sago starch and 90 minutes for arenga starch where previously made starch moisture content of 20%. The rate of sineresis was measured by using centrifuge method, whereas the characteristics of the texture was measured by using texture analyzer. Further analysis was the measurement of water content of starch gels using the oven method and measurement of water activity (aw) using the aw meters. Result of RVA measurement show that HMT can increase the gelatinization temperature, lower breakdown and increasing the setback. This research proved that HMT increases the rate of sineresis of sago and arenga starch gel and can make the texture more rigid. In addition, modification of HMT also increases the fragility of the gels and the moisture content was decreases. Decreasing in aw also occur due to the influence of the HMT. The value of the lowest aw occurred at Sagu HMT starch gel although the rate of decline in the value of the highest aw occurs in the sagu alami starch. Based on the results of the study it can be concluded that the Sagu HMT starch sensitive to heat treatment compared to Aren HMT starch, sagu alami and arenga starch. This is apparent from the highest of increasing a rate of syneresis, increasing in the rate of the elastic modulus, the highest of declining the rate of the strains value, and the highest of the rate of gel moisture content decreasing.
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Judul: A Continuous Vaccination Strategy in the SVIR Epidemic Model
Abstrak: Vaccination is conducted to minimize the spread of a disease. The vaccination is usually done several times within a fixed time interval. In the SVIR model, it is assumed that individuals do not get immediate immunity following a vaccination program. So according to process of vaccination on SVIR model, there are two strategies, i.e. the continuous vaccination strategy (CVS) and the pulse vaccination strategy (PVS). In this study, only the CVS strategy in epidemic model SVIR is considered. Results of the study indicate that dynamics of the CVS system depends on the basic reproductive number. If the basic reproductive number is less than one, then the disease-free fixed point is asymptotically stable. It means that the disease will eventually disappear from the population. Conversely, if the basic reproductive number is greater than one, then the endemic fixed point is asymptotically stable, which means that the disease will remain exist in the population. Simulation result shows that the vaccination would minimize the spread of disease by reducing the basic reproductive number. If the time for the vaccinated recipients to obtain the immunity, as well as a possibility of vaccinated recipients to be infected are neglected, then the disease will be eradicated. This condition is called an over-evaluating effect of vaccination.
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