Judul: Pengembangan Edible Film Komposit Pektin/Kitosan dengan Polietilen Glikol (PEG) sebagai Plasticizer
Abstrak: Interest in maintaining food quality while reducing packaging waste has encouraged further research on edible films. Considerable attention has been given to pectin because it is widely available from underutilized agricultural waste material and is readily modified through demethylation to form excellent films. The scope of composite films made from pectin and other polysaccharides was widened to include chitosan for several reasons. The aims of this study were to prepare homogenous pectin/chitosan composite edible films, characterize and investigate the effect of different pectin to chitosan ratio on film properties. Pectin/chitosan composite edible film with PEG (10%) as plasticizer was prepared by solution casting method in this study. Five pectin to chitosan ratios (100:0, 75:25, 50:50, 25:75, 0:100) were used. The prepared films were characterized in terms of physicochemical and mechanical properties. Result showed that as chitosan content in composite edible film increased; pH, yellowish color, film thickness, and elongation percentage increased, while tensile strength and water vapor transmission rate decreased. PEG addition as plasticizer in edible film increased film thickness, elongation percentage, and water vapor transmission rate, whereas water activity of the plasticized film decreased.
Keyword: 

Judul: Pembuatan dan Karakterisasi Film Biodegradabel dari Kitosan/PLA (Poly Lactic Acid) dengan Pemlastis Polietilen Glikol (PEG)
Abstrak: Plastic has many advantages such as good mechanical and barrier characteristics, cheap, easy to form, and flexible in application, so it becomes the most used material as food packaging. Unfortunately, plastic waste is difficult to be degraded in nature, therefore polluting the environment. Moreover, global warming issue has driven to create an eco-friendly packaging such as biodegradable plastics made from renewable resources. The objective of this research was to develop biodegradable plastic made from chitosan and poly(lactic acid) (PLA) with the addition of poly (ethylene glycol) (PEG) as plasticizer. The main goal of these blends is to improve the water vapor barrier of chitosan by blending with PLA and to improve the elasticity of chitosan/PLA blended films. The obtained films were characterized in terms of physicochemical and mechanical properties including water activity (aw), thickness, tensile strength, elongation at break, and water vapour permeability (WVP). Moreover, Scanning Electronic Microscopy (SEM) and Differential Scanning Calorimetry (DSC) were used to confirm the miscibility of PLA and chitosan. Films of chitosan/PLA blends had aw values range from 0.71 until 0.76. Generally, the blend films prepared with lactic acid as chitosan solvent were thicker than those prepared with acetic acid as chitosan solvent. The same phenomenon was observed in addition of PEG, where films containing PEG as plasticizer were thicker than those without PEG. The tensile strength and elongation at break of the obtained films decreased with the addition of PLA and PEG. It appeared that the obtained films produced with lactic acid as solvent and with the addition of PEG were more elastic than those produced with acetic acid as chitosan solvent and without the addition of PEG. In term of barrier properties, the WVP value of film chitosan/PLA ranged from 111.8 to 208.9 gr/m2/day for films prepared with lactic acid as chitosan solvent and from 233.3 to 358.15 gr/m2/day for films prepared with acetic acid as solvent. Furthermore, the observation on microstructure of the chitosan/PLA composite films, conducted with SEM, has revealed that PLA particles have been well distributed in chitosan matrix. However, the average diametre of PLA particles was in the range of 2 – 3 m, therefore this blending was categorized as microcomposites.
Keyword: 

Judul: Cycle Hamilton pada Graf Lengkap, Graf Regular, dan Graf 2-Connected 4-Regular Berorder Kurang dari Sepuluh
Abstrak: Suatu graf disebut graf Hamilton apabila graf tersebut memuat cycle Hamilton, yaitu cycle yang melewati setiap vertex tepat satu kali. Menentukan keberadaan cycle Hamilton pada suatu graf dapat menggunakan syarat cukup yang berupa teorema-teorema yang telah diperkenalkan sejak tahun 1950-an. Beberapa syarat cukup yang dibahas dalam karya ilmiah ini adalah syarat cukup yang berhubungan dengan graf lengkap dan graf regular. Suatu graf lengkap berorder 𝑛������ ≥ 3 dan graf r-regular berorder 𝑛������ ≤ 2𝑟������ + 1 merupakan graf Hamilton, Karena kedua graf tersebut memuat cycle Hamilton. Selanjutnya, syarat cukup tersebut digunakan untuk menentukan keberadaan cycle Hamilton pada graf 2-connected 4- regular berorder kurang dari 10.
Keyword: graf Hamilton, graf regular, graf lengkap, graf 2-connected 4-regular