In a simple and instant procedure for detecting fish freshness, a hydrogel and hydrophilic pectin matrix membrane was used successfully as an optical pH sensor by immobilizing the chromoionophore ETH 5294 (CI), which is very selective and sensitive for the membrane. The Pe/CI optical pH sensor exhibited excellent linearity between pH 5 and pH 9, with a sensor response time of 5 min and reproducibility of 1.49% relative standard deviation (RSD). The sensor showed response stability for 15 days and a response reduction of 8.6%. The sensor’s capability was demonstrated by the detection of fish freshness for 17 days at 4 °C.

A novel and simple optical biosensor to detect triglycerides (TGs) has been successfully constructed by using pectin hydrogel membrane as the indicator pH and chromoionophore ETH 5294 (CI), with lipase as the catalyst. The enzymatic working system against TGs releasing H+ ions will affect the color absorbance of CI. The characterization results show that a TG biosensor has the optimum condition and sensitivity at the phosphate buffer concentration of 50 mM, pH 7, and enzyme loading of 60 μg. The biosensor works at the tripalmitin (TP) concentration range of 100–400 mg/dL. With the sensitivity of 0.001 (∆A/(mg/dL)), the biosensor response reaches stability after five minutes, and the limit of detection (LOD) of the TG optical biosensor is 15 mg/dL. Relative standard deviation (RSD) in a reproducibility test was 2.5%, with a 15-day lifespan.

Pectin from Arabica Gayo coffee pulp has been successfully isolated using citric acid as a solvent. The pectin extracted from the coffee pulp is determined by the extraction conditions. This study aims to produce pectin from dried coffee extract using citric acid using two factors, namely the difference factor of citric acid (1: 5 and 1: 20 b/v) and extraction time 75 and 150 minutes. The optimum ratio of Arabica Gayo coffee pulp with citric acid was 1:20 b/v with rendemen 7,8 % with 125 minute extraction time and at the temperature of 80 °C and pH 4. The methoxyl content of isolated pectin was 12.71 % and has been determined as high methoxyl pectin (HMP). The result of analysis with FTIR is known that the extract produced is pectin with comparison with pectin standard. The pectin has been used as a matrix membrane and showed its smooth surface gel form and smaller diameter from scanning electron microscopy (SEM).1

A tri-enzyme system consisting of choline kinase/choline oxidase/horseradish peroxidase was used in the rapid and specific determination of the biomarker for bacterial sepsis infection, secretory phospholipase Group 2-IIA (sPLA2-IIA). These enzymes were individually immobilized onto the acrylic microspheres via succinimide groups for the preparation of an electrochemical biosensor. The reaction of sPLA2-IIA with its substrate initiated a cascading enzymatic reaction in the tri-enzyme system that led to the final production of hydrogen peroxide, which presence was indicated by the redox characteristics of potassium ferricyanide, K3Fe(CN)6. An amperometric biosensor based on enzyme conjugated acrylic microspheres and gold nanoparticles composite coated onto a carbon-paste screen printed electrode (SPE) was fabricated and the current measurement was performed at a low potential of 0.20 V. This enzymatic biosensor gave a linear range 0.01–100 ng/mL (R2 = 0.98304) with a detection limit recorded at 5 × 10−3 ng/mL towards sPLA2-IIA. Moreover, the biosensor showed good reproducibility (relative standard deviation (RSD) of 3.04% (n = 5). The biosensor response was reliable up to 25 days of storage at 4 °C. Analysis of human serum samples for sPLA2-IIA indicated that the biosensor has potential for rapid bacterial sepsis diagnosis in hospital emergency department.

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A simple optical pH sensor based on immobilization, Dioscorea alata L. anthocyanin methanol extract, onto a pectin–chitosan polyelectrolyte complex (pectin–chitosan PEC), has been successfully fabricated. The optical pH sensor was manufactured as a membrane made of pectin–chitosan PEC and the extracted anthocyanin. This sensor has the highest sensitivity of anthocyanin content at 0.025 mg/L in phosphate buffer and 0.0375 mg/L in citrate buffer. It also has good reproducibility with a relative standard deviation (%RSD) of 7.7%, and gives a stable response at time values greater than 5 min from exposure in a buffer solution, and the sensor can be utilized within five days from its synthesis. This optical pH sensor has been employed to determine saliva pH of people of different ages and showed no significant difference when compared to a potentiometric method.

Abstrak- Cangkang telur ayam yang dihasilkan di Samarinda pada tahun 2013 yaitu 307,22 ton dan sebagian besar hanya dibuang begitu saja menjadi sampah. Pada penelitian ini cangkang tersebut diaktivasi secara fisika kemudian dimanfaatkan sebagai adsorben untuk menurunkan bilangan asam dan bilangan peroksida pada minyak jelantah. Proses adsorpsi minyak jelantah dilakukan dengan variasi massa adsorben yaitu 7, 8, 9 dan 10 gram dan waktu pengadukan selama 45, 60, dan 75 menit. Berdasarkan hasil penelitian diperoleh kondisi optimum untuk penurunan bilangan asam pada penggunaan massa adsorben sebesar 9 gram dan waktu pengadukan selama 60 menit menghasilkan bilangan asam sebesar 0,3923 mgKOH/g dengan penurunan bilangan asam sebesar 91%, sedangkan untuk bilangan peroksida mengalami penurunan sebesar 58% dengan nilai sebesar 7,516 mek O2/kg. Bilangan asam dan bilangan peroksida yang diperoleh pada kondisi optimum tersebut telah memenuhi standar SNI 3741-2013 untuk minyak goreng yaitu 0,6 mgKOH/g dan 10 mek O2/kg. Kata Kunci: adsorpsi, cangkang telur ayam, bilangan asam, bilangan peroksida, minyak jelantah  Abstract- Chicken egg shells produced in Samarinda in 2013, as much as 307.22 tons and mostly just dumped it into the trash. In this study, the shell activated and then used as an adsorbent for reducing the acid value and peroxide value on frying oil. Frying oil adsorption process was done by varying the mass of adsorbent that is 7, 8, 9 and 10 gram and time stirring for 45, 60 and 75 minutes. The research showed the optimum conditions for a decrease in acid number on the use of adsorbent mass of 9 grams and the time of stirring for 60 minutes to produce the acid value of 0.3923 mgKOH / g with a decrease in acid number of 91%, while for the peroxide value decreased by 58% with a value of 7.516 meq O2/kg. Numbers acid and peroxide obtained at the optimum condition has met the SNI 3741-2013 standards for edible oil is 0.6 mgKOH / g and 10 meq O2/kgKeywords: adsorption, chicken egg shells, acid value, peroxide value, frying oil

Tulisan ini akan mengkaji secara khusus tentang keterampilan mengajar guru dan motivasi belajar siswa sebagai faktor yang diduga kuat mempengaruhi hasil belajar. Berdasarkan hasil analisis data dengan menggunakan regresi ganda dan korelasi product moment dimana data yang dikumpulkan melalui metode survey dengan menggunakan angket jawaban tertutup terhadap 54 Siswa pada salah satu Sekolah Menengah Kejuruan Swasta di Bandung sebagai responden. Hasil analisis data tersebut menunjukkan bahwa keterampilan mengajar guru dan motivasi belajar siswa berkorelasi kuat terhadap hasil belajar secara parsial maupun simultan. Hasil penelitian ini dapat memberikan implikasi terhadap proses belajar mengajar dalam hal ini adalah guru dan siswa. Demikian pula pengkaji pendidikan untuk dapat mempertimbangkan keterampilan mengajar dan motivasi belajar sebagai variabel-variabel prediktor yang kuat dalam rangka meningkatkan hasil belajar siswa yang lebih baik. Kata Kunci: keterampilan mengajar guru, motivasi belajar, hasil belajar. TEACHERS TEACHING SKILLS AND STUDENT LEARNING MOTIVATION  AS A DETERMINANT OF THE LEARNING OUTCOMES This article will discuss teacher teaching skills and student learning motivation as the factors strongly assumed to influence learning outcomes. Based on the results of multiple regression analysis and product moment correlation of data collected through a survey method with a close-ended questionnaire distributed to 54 respondents in one of private vocational high school students in Bandung, it is found that teacher teaching skills and student learning motivation were strongly correlated with learning outcomes, both partially and simultaneously. The findings can have implications on the teaching and learning process, in this case teachers and students. The implications are also for education researchers to consider teaching skills and learning motivation as strong predictors or variables of better students’ learning outcomes.Keywords: teachers teaching skills, learning motivation, learning outcomes.