THERMAL PROCESS LITERATURE REVIEW

14

H. THERMAL PROCESS

Heating applied in food processing and preservation has the objective to eliminate or reduce microbes’ activity to grow, reproduce, and decompose nutritional components in food products. In addition, heating is also intended to obtain better aroma, texture, and appearance Lewis 2006. There are several methods of food wet heating treatment, such as blanching, sterilization, and pasteurization. Blanching is a cooking process wherein the food substance, usually a vegetable or fruit, is plunged into boiled water, removed after a brief, timed interval, and finally plunged into iced water or placed under cold running water shocked to halt the cooking process Fellows 2000. Blanching is applied in the preparation process of commercial green grass jelly by its vendors. The objective of this process is to decrease initial amount of microbes, inactivate plant enzymes, and soften the tissue in order to ease hydrocolloid extraction. Boiling is heating in boiling water at 100°C for a few minutes. In this method, heatresistant bacterial spores can still be alive after boiling for several hours Hariyadi 2000. Steaming is heating with hot steam at 100°C for a few minutes. Steaming works by boiling water continuously, causing it to vaporize into steam. The steam then carries heat to the nearby food, thus cooking the food. The food is kept separate from the boiling water but has direct contact with the steam, resulting in a moist texture to the food. Sterilization is a condition that is obtained from food processing by using a high temperature in a period of time, so that no living microorganisms exist at normal storage temperatures. The products undergo sterilization may still contain spores of bacteria, but in dormant not actively reproductive conditions, so its presence does not harm if the product is stored under normal conditions. Commercial sterilization standard used is 121°C for 15 minutes Lewis 2006. Pasteurization is a relatively mild heat treatment, in which food is heated to below 100 o C. In low acid foods pH 4.5, it is used to minimize possible health hazards from pathogenic microorganisms and extend shelf life of foods for several days. In acidic foods pH 4.5, it is used to extend the shelf life for several months by destruction of spoilage microorganisms yeast or mold and enzyme inactivation. In both types of food, minimal changes are caused to the sensory characteristics or nutritive value Fellows 2000. Thermal treatment used in this research is pasteurization with steaming at 100 o C for 5 minutes recommended by Pramitasari 2012. In previous research, boiling green grass jelly for 5 minutes resulted destruction of commercial green grass jelly structure and color change to be brownish green at the temperature which had not reached 100°C or about 70°C. Therefore, boiling is ineffective in improving the quality of green grass jelly. On the other hand, steaming of green grass jelly for 5 minutes resulted color change from green to be brownish green, but green grass jelly structure was not destroyed. Therefore, steaming is an effective thermal process. Pramitasari 2012 reported that steaming green grass jelly at 100°C for 5 minutes could reduce the number of total microbes on average of 1.07 to 1.10 log CFUg, the amount of E. coli on average of 1.00 to 1.18 log CFUg, and the number of Staphylococcus sp. on average of 0.29 to 0.71 log CFUg. Low decrease in microbial amounts was caused by lowest rate of heat penetration since the heating instrument was so simple, using conventional steamer pot. However, this steaming treatment can increase the gel syneresis on average of 7.82 – 9.03. The gel strength of green grass jelly after steaming treatment decreased on average of 1.97 – 2.99 gcm 2 . 15

II. RESEARCH METHODOLOGY

A. MATERIALS A D TOOLS 1. Production Materials

The materials used in the production of green grass jelly were green grass leaves Premna oblongifolia Merr. from Muara Empang Bogor, bottled water with the pH about 7.67, NaHCO 3 , sodium alginate, Low Methoxyl Pectin LMP, and mixture of kappa and iota carrageenan from Class Kimia Jakarta, and CaCO 3 from Brataco.

2. Chemicals

The materials used in the analysis were phosphate buffer solution pH 4.00 and pH 7.00, methanol 85, FolinCiocalteau reagent, sodium carbonate 5, gallic acid, ascorbic acid, methanol 99.9, DPPH reagent, acetone 99.8, sodium phosphate, enzyme thermamyl Sigma A9972, HCl 4 N, enzyme pepsin 284401 JT Baker, NaOH 4 N, pancreatin EC 232 4689 Merck, distillate water, ethanol 78 , and ethanol 95.

3. Tools

The tools used in this study were spatula, watch glass, analytical balance, basins, filter cloth, plastic stirrers, spoons, beaker glass, measuring cylinder, HDPE plastic cups, glass stirrers, HDPE plastic, conventional steamer pot, water bath, pH meter, LV Brookfield Viscometer, Stevens LFRA Texture Analyzer, Chromameter Minolta CR 200, vortex, test tube, cuvette, conical funnel, spectrophotometer, centrifuge, refrigerator, aluminum bowls, erlenmeyer flask, volumetric flask, volumetric pipette, micropipette, shaking incubator, drop pipette, agitators, filter paper Whatman No. 40, a filter with a vacuum pump, oven, electric furnaces, porcelain bowls, desiccator, small trays, small glasses, and small spoons.

B. RESEARCH METHOD

This study was conducted in several stages. The first study was conducted to determine the gelling time in order to standardize all of green grass jellies’ gelling time in this study by considering viscosity analysis. The next stage was determination of concentration NaHCO 3 concentration used in the production of green grass jelly by considering physical properties. The next stage was determination of the hydrocolloid and CaCO 3 concentration with steaming treatment by considering physical and organoleptic properties. The last stage was the observation of green grass jelly’s chosen formula on the functional properties with the effects of steaming. The flow chart of this research can be seen on Figure 9.