Judul: Karakterisasi Emulsi Minyak Sawit Merah yang Distabilisasi Protein Whey dan Kinetika Perubahan Fisika-Kimianya Selama Penyimpanan
Abstrak: Red Palm Oil (RPO) is a carotenoid-rich edible oil that can potentially be used as a source of natural provitamin A, especially β-carotene. However, the use of RPO nowadays is still limited because it is susceptible to storage damage (rancidity and decreased β-carotene content) and has high hydrophobicity (making it difficult to apply to water-based food systems). Emulsification of RPO in the oil-in-water (O/W) system is expected to overcome these weaknesses by protecting RPO from external factors and “carrying” RPO in different phases. Based on that, this study generally explored the potential of whey protein (WP)-stabilized emulsions to serve as “carrier systems” for RPO. To achieve the general objective, this study evaluated the physical properties and stability of the developed RPO emulsion and the stability of RPO’s β-carotene and lipids in it. A literature review was conducted to review the potential for WP-stabilized emulsification to enhance the stability of RPO carotenoids. Based on the results, the low stability of carotenoids, including β-carotene, is related to their molecular structure, which consists of conjugated double bonds with high electron affinity. Carotenoid degradation is caused by interactions or reactions between the molecular structure and external factors such as oxygen, light, and heat. The study’s results indicated that O/W emulsions stabilized with WP have the potential to become an RPO carrier system. RPO emulsification in this study was carried out using three types of WP emulsifiers (i.e., WPCa, WPCb, and WPI) at several concentration levels (i.e., 2.5%, 5%, 10%, and 15% w/v) by employing a catastrophic phase inversion technique. Thus, 12 WP-stabilized RPO emulsion systems were generated in this study. The physical properties of the emulsions were analyzed based on their droplet size characteristics, droplet charge characteristics, and rheological properties (flow behavior and dynamic viscoelastic properties). Then, the droplet size characteristics were further evaluated for change in the storage and centrifugation tests. The results showed that the characteristics and physical stability of the 12 RPO emulsions produced varied depending on the type and concentration of WP emulsifier used. Based on the droplet size, 4 of the 12 emulsions prepared were mini-emulsions (mean particle size (ADS) = 384.92–480.44 nm), while the others were macroemulsions (ADS = 653.44–2029.44 nm). The results showed that the physical stability of the RPO emulsion could be explained using the relationship between the droplet characteristics and their rheological properties. However, observation of the physical appearance is still necessary (i.e., presence or absence of creaming or “oiling off”). Based on the storage and centrifugation tests, it was found that the RPO mini-emulsion produced tended to experience destabilization through the coalescence mechanism. In contrast, the RPO macroemulsion underwent the Ostwald ripening mechanism. In addition, the RPO mini-emulsion had better physical stability than the RPO macroemulsion. Among the produced systems, the 15% WPCb-stabilized RPO mini-emulsion had the best physical stability with an initial ADS of 384.92±16.88 nm. The stability of RPO’s β-carotene and lipids in the 15% WPCb-stabilized RPO mini-emulsion was evaluated using an accelerated shelf-life test approach by exposing the system to conditions that accelerate the rate of deterioration. Several other physical properties were also
Keyword: Coalescence, Lipid Oxidative Stability, Photodegradation, Rheology, Thermal Degradation

Judul: Experimental Investigation on Physical Stability of RPO-in-Water  Emulsion Stabilized by Protein and SiO2 Nanoparticles
Abstrak: As a source of Vitamin-A precursor, the stability of red palm oil (RPO) against oxidation was addressed to be improved. Emulsion containing 10% (v/v) RPO was produced using two-step homogenization, namely at 9000 rpm and 18000 rpm. This research aims to study the effect of emulsification process of RPO to enhance its stability. The used emulsifiers are whey protein concentrate (WPC), soy protein isolate (SPI), and SiO2 nanoparticles with concentration from 2.5% to 15%. The physical stability of the resulting emulsion is analyzed based on the parameters of surface colour, separation index, flow properties, and droplet size distribution. Results showed that higher emulsifier concentration (c) contributes to improve emulsion stability during storage. In this study, emulsion stabilized by SiO2/SPI 15% (SSP15) and SPI 5% (SPI5) were found as the most stable emulsion based on tested physical attributes.
Keyword: emulsion, red palm oil, SiO2 nanoparticle, whey protein concentrate, soy protein isolate

Judul: Closed Knight’s Tour pada Papan Catur Berbentuk Persegi Panjang dengan Ukuran Maksimal 8 × 8
Abstrak: Closed Knight’s Tour merupakan langkah kuda yang mengunjungi setiap kotak pada papan catur tepat satu kali dengan langkah kuda berawal dan berakhir pada kotak yang sama. Graf yang terbentuk dari closed knight’s tour dinotasikan sebagai graf G(m,n), dengan m adalah banyaknya baris dan n adalah banyaknya kolom. Graf tersebut memuat Hamiltonian cycle. Sebuah graf terhubung G adalah graf bipartite jika dan hanya jika graf tersebut tidak memiliki cycle dengan panjang ganjil. Papan catur yang memenuhi syarat cukup untuk memiliki closed knight’s tour adalah papan catur berukuran 5 × 6, 5 × 8, 6 × 6, 6 × 7, 6 × 8, 7 × 8, dan 8 × 8.
Keyword: bipartite, closed knight’s tour, hamiltonian cycle, knight’s tour, teori graf