Judul: Study on the potency of acetate, sodium benzoate, and potassium sorbate as preservatives for tofu
Abstrak: Tofu is one of Indonesian traditional food which is made from soybeans (Glycine max). Tofu stored in the refrigerator has shelf life for about 2 days and only a half day when it stored at ambient temperature. This is the reason why illegal practice of the using formalin has occured in Indonesia. The objective of this research was to evaluate the capability of sodium benzoate, potassium sorbate, and acetic acid as preservatives for tofu. The expected result is giving an alternative of method in preserving tofu with legal food additive. The concentration of sodium benzoate and potassium sorbate that was used in this research is 40% of ADI. Tofu was divided into five main treatments, tofu that soaked in water, acetic acid, acetic acid-sodium benzoate, acetic acid-potassium sorbate, and acetic acid-sodium benzoate-potassium sorbate. Several tests such as, texture analysis, total plate count (TPC), pH measurement, color measurement, and organoleptic test, were conducted to measure the effectivity of each preservative to prolong the shelf life of tofu. TPC assay showed that all of the combinations of preservatives were effective to reduce the number of microbes. The texture of tofu became soften after soaked in acetic acid and analyzed using Texture Analyzer. The result of texture analysis showed that the combination of acetic acid-sodium benzoate had the softest texture (0.46 N) compared to the other treatments. pH measurement showed that acetic acid had the lowest value (4.16) compared to the other treatments. The result of the research showed that acetic acid 1.5% (v/v) did not have the capacity as preservative for tofu. The use of acetic acid 1.5% (v/v) caused sour taste that made tofu could not be accepted by consumers. However, all of the combination of preservatives showed good effect in preserving tofu when stored at room temperature. Soaking sour tofu in 3% (w/v) salt solution for 3 minutes could increase the acceptance of consumers.
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Judul: Aplikasi kitosan dengan penambahan esensial oil kunyit sebagai pengawet dan edible coating produk tahu
Abstrak: Tofu is a nutritious and digestible food that has been widely consumed in Indonesia. However it is a perishable food that has a short shelf life due to its rich nutrients and high moisture content. This characteristic makes both producers and consumers would like to prolong it. The objective of this research is to apply chitosan enriched with Curcuma Essential Oil (CEO) as curdling agent and as antimicrobial coating to prolong the shelf-life of tofu. Physicochemical film and antimicrobial properties of chitosan are studied. Antimicrobial activity was tested against food pathogenic and spoilage bacteria, namely Escherichia coli and Bacillus cereus, respectively. All characteristics of tofu except texture in the sensory evaluation, were not significantly differences between the chitosan-tofu, chitosan-EO tofu and control tofu. The obtained results revealed that the application of chitosan enriched with CEO as coating and curdling agent had a little effect on the quality attributes. The shelf life of chitosan coated tofu is longer by 3 days than control tofu without chitosan
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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