Ratnawati

Physical, thermal and functional properties of flour derived from Ubi Gembili (Dioscorea esculenta L.) tubers grown in Indonesia

Gembili ( Dioscorea esculenta L.) tuber is one of the important food sources in term of cultural, nutritional and economic perspectives for the people in the Africa, Caribbean islands, Asia, and Oceania regions. The tubers can be eaten after being boiled, roasted, fried or cooked. However, there is lack of information on the advanced utilizations of the tubers as raw material in the manufacture of modern foods. This study aims to characterize the physical, functional and thermal properties of Gembili flour, so that this information can be used as the basis in the development of novel foods. The microstructure, crystallinity, gelatinization temperature, swelling power and solubility of the flour were determined. The electron microscope observation revealed that Gembili flour consisted of smooth surface oval granules, which were light brown in color and having 23 µm average diameter. They are comprised of polygonals or some clusters of irregular fragments. Similar to most of tuber flours, Gembili flour also exhibited B-type crystallinity with approximately 31 ±3.7% crystallinity. The gelatinization temperature of Gembili flour was high and being comparable to that of cereal flour. The enthalpy of gelatinization of Gembili flour (9.52 ±0.80 J.g -1 ) was comparable to that of Dioscorea alata . Unfortunately, Gembili flour exhibited low swelling power (3.90 ±0.01 g.g -1 ). The Gembili flour granules were highly soluble in water (11.07 ±0.05%). Based on those reported properties, Gembili flour can be a suitable raw material for the manufacture of bakery, cookies, noodle and infant foods.

Optimasi Proses Ozonasi pada Depolimerisasi κ-Karagenan dengan Metode Respon Permukaan

A bstract OPTIMIZATION OF OZONATION PROCESS FOR κ-CARRAGEENAN DEPOLYMERIZATION USING RESPONSE SURFACE METHODOLOGY . The objective of this research is to optimize the operating parameters in depolymerization of κ-carrageenan by ozone treatment. The optimization is done by using Box-Bhenken Design (BBD) model with ozonation time (5-15 minute), pH (3-11) and temperature (20-40 o C) as the independent variables.The response of ozonation process is the degree of d epolymerization of κ-carrageenan (DP). The initial molecular weight of refined κ-karagenan was 271 kDa. The κ-carrageenans powder was completely dissolved in distilled water to form 1% (weight/volume). The experiments were carried out in a 2000 ml of a glass reactor with an ozone gas sparger. The inlet ozone concentration was 80±2 ppm. The result shows that ozonation time , pH and temperature have significant effects during ozonation process (p< 0.05). Analysis of variance show s that the experimental data fit the model very well with the R 2 value of 0.98. T he optimum conditions during ozonation process are achieved at the reaction time of 15 min, ozonation pH of 3 and reaction temperature of 25 o C. Under these optimum conditions the DP of κ -carrageenan is 91.513 % . Keywords: depolymerization; κ-carrageenan ; optimization; ozonation process Abstrak Tujuan penelitian ini adalah menentukan kondisi optimum parameter operasi depolimerisasi κ-karagenan dengan perlakuan ozonasi. Optimasi dilakukan dengan menggunakan model statistika Box-Bhenken Design (BBD) dengan variabel yang digunakan yaitu waktu ozonasi (5-15 menit), pH (3-11), dan suhu (20-40 o C). Respon dari proses ozonasi adalah derajat depolimerisasi κ-karagenan (DP). Berat molekul awal refined κ-karagenan adalah 271 kDa. Sampel κ-karagenan dilarutkan secara sempurna dalam air distilasi dan konsentrasi diatur 1% (berat/volume). Percobaan dilakukan dalam reaktor gelas volume 2000 ml yang dilengkapi dengan sparger gas ozon. Konsentrasi gas ozon yang masuk adalah 80±2 ppm. Hasil penelitian menunjukkan bahwa waktu ozonasi, pH, dan suhu berpengaruh secara signifikan terhadap proses ozonasi (p<0,05). Analisis varian menghasilkan ketelitian yang tinggi antara data eksperimen dan prediksi, dengan nilai koefisien R 2 = 0,98. Kondisi optimum diperoleh pada waktu ozonasi 15 menit, pH ozonasi 3 dan temperatur reaksi 25 o C. Pada kondisi optimum ini diperoleh DP κ-karagenan sebesar 91,513 % . Kata kunci: depolimerisasi; κ-carrageenan;optimasi; proses ozonasi

H2O2/UV Photo-Oxidation of Gadung (Dioscorea Hispida Dennst.) Starch and its Product Physicochemical Characterization

This work aimed to study the preparation and physicochemical properties characterization of oxidized gadung starch obtained from oxidation process implementing combined H 2 O 2 -UV irradiation. The photo-oxidation process was carried out in a well-mixed slurry reaction system at ambient temperature. The extent of oxidation was determined based on the carboxyl and the carbonyl contents of the oxidized gadung starch. The results show that oxidation process altered the carbonyl and carboxyl contents of the starch. Except the morphology of the starch, the swelling power, solubility and gelatinization temperature of the starch were severely affected by H 2 O 2 /UV oxidation process.

Effect of catalyst concentration and reaction time on the extraction of glucomannan from porang (Amorphophallus oncophyllus) flour via acid hydrolysis

High demand of glucomannan for various applications has attracted the attention of researchers to look for efficient extraction method from its botanical sources. The aim of this study is to investigate the effect of catalyst concentration and reaction time on the yield and purity of glucomannan, and profile of reducing sugar during glucomannan extraction from crude porang flour via acid hydrolysis. The effect of catalyst concentration was found to be more pronounced over the effect of reaction time. When catalyst concentration was varied from 0.03125 to 1 M, extraction of glucomannan from porang flour for 1 hour at 60°C yielded 40.5 to 70% glucomannan with purity of 47.35 to 90.18% (w/w). The yield and purity of glucomannan obtained from extraction using catalyst concentration of 1 M for 0.25 to 3 hour ranged between 49 to 66.67% and 58.32 to 90.18% (w/w), respectively. Reduction in glucomannan yield and purity observed at high catalyst concentration and prolong reaction time was likely to be due to over-decomposition. Glucomannan with highest purity (90.18% w/w) was obtained at 66.67% yield from acid hydrolysis of porang flour using 0.5 M hydrochloric acid solution with flour:water ratio of 1:50 at 60°C for 1 hour.