Mount Sinabung volcanic ash is a basic material that can be used to produce silicon dioxide (SiO 2). SiO 2 can be used as a building raw material as well as in food and beverage packaging. To produce SiO 2, the volcanic ash of Mount Sinabung must be synthesized using the coprecipitation method. The result of this process produces SiO 2 content as much as 48%, a formed function group that states the existence of SiO 2 namely Si-O-Si and Si-O at absorption of 1095.57 cm-1 and 798.53 cm-1. From the results of SEM can be seen the morphology of SiO 2 formed. In the XRD results, the phase of SiO 2 is amorphous.

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The purpose of this study was to utilize cellulose from tea waste as nanocrystalline cellulose (NCC), which is used as a filler in poly(vinyl) alcohol (PVA) nanocomposites. To obtain the NCC, a chemical process was conducted in the form of alkali treatment, followed by bleaching and hydrolysis. Nanocomposites were formed by mixing PVA with various NCC suspensions. With chemical treatment, lignin and hemicellulose can be removed from the tea waste to obtain NCC. This can be seen in the functional groups of cellulose and the increase in crystallinity. The NCC had a mean diameter of 6.99 ± 0.50 nm. Furthermore, the addition of NCC to the PVA nanocomposite influenced the properties of the nanocomposites. This can be seen in the general increase in opacity value, thermal and mechanical properties, and crystallinity, as well as the decrease in the value of the swelling ratio after adding NCC. This study has revealed that NCC from tea waste can be used to improve the physicochemical properties of PVA film.

This study aims to: (1) to find out how much the optimal purchase of soybean raw materials in Tofu Elsa Jaya Industry, (2) to know when the time of ordering back raw materials of soybeans. Sources of information obtained from the results of interview processing. This study is a case study so that the leadership of the Tofu Elsa Jaya Industry serve as a source to obtain information in accordance with the needs of researchers. Data analysis technique used is descriptive analysis and analysis of EOQ, TIC, Safety Stock and ROP. There are several results obtained in this study. First, the amount of soybean raw material needs in 2018 is 115,934 kg. Second, the optimal order quantity of soybean raw material according to EOQ calculation is 28.310 kg per one time message and frequency of purchase that is 4 times the message. Third, in order not to run out of raw materials, the Tofu Industry Elsa Jaya must prepare the security supplies as much as 1,337 kg and order back when the supply of soybean raw material in the warehouse lived 4.710 kgABSTRAKPenelitian ini bertujuan untuk: (1) untuk mengetahui berapa jumlah pembelian bahan baku kacang kedelai yang optimal pada Industri Tahu Elsa Jaya,(2) untuk mengetahui kapan waktu pemesanan kembali bahan baku kacang kedelai.Sumber informasi diperoleh dari hasil pengolahan wawancara.Penelitian ini adalah studi kasus sehingga pimpinan Industri Tahu Elsa Jaya dijadikan sebagai sumber untuk memperoleh informasi sesuai dengan kebutuhan peneliti.Teknik analisis Data yang digunakan adalah analisis deskriptif dan analisis EOQ, TIC, SafetyStock dan ROP. Terdapat beberapa hasil yang diperoleh dalam penelitian ini.Pertama, jumlah kebutuhan bahan baku kacang kedelai pada tahun 2018 yakni 115.934 kg. Kedua, jumlah pemesanan bahan baku kedelai yang optimal menurut perhitungan EOQ yakni 28.310 kg per satu kali pesan dan frekuensi pembelian yakni sebanyak 4 kali pesan. Ketiga, agar tidak kehabisan bahan baku maka Industri Tahu Elsa Jaya harus menyiapkan persedian pengaman sebanyak 1.337 kg dan pemesanan kembali saat persediaan bahan baku kacang kedelai di gudang tinggal 4.710 kg.

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