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: Sifat Fisik Emulsi Minyak Sawit Merah Distabilisasi
Protein Whey
Abstrak: Whey protein-stabilized oil-in-water (O/W) emulsion presumed feasible to be red palm oil (RPO) “carrier” system. RPO has the potential to be a natural source of pro-vitamin A but its utilization is still limited since RPO tend to have low stability during storage, and its high hydrophobicity nature limits its application on fat/oil-based food. The formation of whey protein-stabilized RPO emulsions (O/W) might overcome those challenges by (i) isolating RPO from the external factors that affect its stability and (ii) “carry” RPO into a non-fat/oil-based food system. For that, a stable whey protein-stabilized RPO emulsion is needed to be a good “carrier” system. This study aimed to (i) develop a stable whey protein-stabilized RPO emulsion with an oil phase content of 30%, (ii) examine and analyze the physical characteristics (visually observed) of emulsions, the characteristics of the emulsion droplets, and both stability during storage, and (iii) evaluate the influence of the droplets characteristics on the physical characteristics of the emulsions and the effect of type and concentration of whey protein used on the physical characteristics of emulsions and its stability. The whey protein-stabilized RPO emulsion was prepared by employing two-steps homogenization with 30% (v/v) oil phase volume fraction. The continuous phase was prepared by making emulsifier solution from two types of whey protein concentrate (WPCa and WPCb) and one type of whey protein isolate (WPI) at four levels of concentration (i.e., 2.5, 5, 10, and 15%; w/v) in deionized water. The emulsions produced were characterized for their droplet characteristics (i.e., average droplet sizes (ADS), droplet sizes distribution, polydispersity index, SPAN, and D-values). The emulsions were then stored at three different temperatures (i.e., 30, 45, and 60 °C), and the droplet characteristics were evaluated after 7 and 14 days of storage. The emulsions stored at 30 °C were also evaluated for their physical (visually observed) stability (i.e., appearance, qualitative rating of destabilization and oil droplet viability, and separation index (SI)). The emulsions with the emulsifier concentration of 15% were further evaluated for their accelerated destabilization rate by the Ostwald ripening and coalescence model. This study was able to form whey protein-stabilized RPO emulsions containing 30% oil phase with good stability. The type and concentration of whey protein used affected the physical characteristics of emulsions, droplet’s characteristics, and the stability of both. The WPCa- and WPCb-stabilized emulsions were more stable, along with lower ADS and SI, than WPI-stabilized emulsions. Besides that, emulsions with higher emulsifier concentrations were more stable, with lower ADS and SI values. The emulsions produced underwent a faster rate of destabilization at higher storage temperatures, and were less stable when stored at above 45 °C. As compared to Ostwald ripening, the coalescence mechanism was thought to be more suitable to explain the destabilization of RPO emulsions tested. Based on its physical appearance, the emulsion with 15% of WPCb was the most stable system, having an SI of 0% after 105 days of storage and initial ADS 398±11 nm. The emulsion also remained stable during extended storage without separation of phase or cream (SI = 0%) up to 220 days of storage. Further
Keyword: coalescence, emulsion destabilization, separation index, whey protein isolate, whey protein concentrate

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. ,,,
Keyword: graf Hamilton, graf regular, graf lengkap, graf 2-connected 4-regular.