Judul: Characterization of The Chemical Constituents and Antioxidant Capacity of Green and Oolong Teas (Camellia sinensis) Manufactured in Thailand
Abstrak: Tea in Thailand most manufactured in northern area, especially Chiang Rai, Chiang Mai, Nan, and Mai Hang Son province. The aim of this study was to determine and compare the chemical compositions and antioxidant capacity of 4 important Thai tea products. A total of 13 of green teas of 2 major cultivars, assamicaand cv. oolong no.12 (chin hsuan oolong) and 26 of oolong tea of 2 major varieties, cv. oolong no. 12 and cv. oolong no. 17 (chin shin oolong) were collected from 18 factories in Chiang Rai province in 2011. The total polyphenol content was determined according to International Organization for Standardization (ISO 14502-1). For antioxidant capacity, DPPH radical scavenging activitiy assay and ferric reducing antioxidant power assay were determined. The catechins content and caffeine content were determined using HPLC by ISO method (ISO-14502-2). Results showed that about 95% of the 39 tea samples manufactured in Thailand had moisture content below 7%, 5% of tea samples being above 7%. The total polyphenol content in green tea was found to vary from 11.86 to 21.19%GAE, while in oolong tea was found in a range of10.22 to 17.57%GAE. The caffeine content in green tea samples were in a range of 1.69 to 3.7%, while in oolong tea samples were in a range of 1.61 to 3.26%. The catechin content in green tea samples were in a range of 8.31-14.08%, while in oolong tea samples were in a range of 6.81-12.46%. The antioxidant capacity in green tea samples was 164.01 mmole TE/100 g dry basis, while in oolong tea samples was about 132.73mmole TE/100 g dry basis. This study provided useful information for the tea industry in Thailand and other countries in processing and selecting a good-quality tea.
Keyword: Antioxidant capacity, Camellia sinensis, Green tea, Oolong tea, Thailand

Judul: Development of Effervescent Green Tea (Camellia sinensis var. sinensis ).
Abstrak: Green tea has high phenolic compound which gives good impact to body’s health, due to its high phenolic compound the taste is slightly bitter, which decrease consumer acceptance. To overcome this problem, effervescent tea was presented. Effervescent is the reaction of acid and base producing CO2 when dispersed in water resulting a fizzing mouthfeel which covering undesired taste and giving other advantages. Discovering the best formulation based on its physical, chemical and sensory properties to increase the consumer acceptance is the objectives of this research. The quality of green tea powder was analyzed, it had bulk density 0.60 ± 0.03 g/mL, solubility 76.82 ± 0.66 %, and color (L*, a*, b*) 64.28 ± 0.45; 2.05 ± 0.11; 27.24 ± 0.41. The TPC (Total Phenolic Content) and moisture content were 5.56 ± 0.06 (% w/w dry basis) and 1.84 ± 0.11 % (wb). The second study was determination of the best formulation, there were 16 formulas which were developed with mixture design technique. The components including stevia (2%) as fixed ingredient, green tea powder (Camellia sinensis var. sinensis) (15-40%), mixture of sodium bicarbonate and citric acid (50-65%) with ratio 1:1, maltodextrin (10-20%). Based on the physical, chemical, and sensory properties the best formula consists of 56% mixture citric acid and sodium bicarbonate, 29% green tea powder, and 15% maltodextrin. This formula then used to make the final product and its quality was determined. The hardness 115.80±4.96 N, color as 0Hue 86.46±0.09, effervescent time 183.33±2.08 second, for pH 5.65±0.01, moisture content 1.92±0.03% (wb) and TPC 2.34±0.058 (% w/w db). Consumer acceptance test was conducted with 100 participants with different background (gender, age, occupation, and education), the acceptability and buying intention were considered high (87% and 74% respectively). In conclusion this product has met the standard of effervescent product and finely accepted by consumer.
Keyword: Effervescent, Effervescent tea, Consumer acceptance, Green tea

Judul: Rancang Bangun Mekanisme Penggetar Untuk Bajak Subsoil Getar Dengan Dua Bilah Bajak
Abstrak: Bajak subsoil merupakan alat pengolahan tanah pertama yang sering digunakan sebelum pembajakan dengan bajak singkal atau bajak piring untuk memecah lapisan keras di lapisan bawah. Alat ini biasanya digunakan pada tanah yang telah mengalamli pemadatan akibat lalu lintas traktor. Alat ini memiliki tahanan tarik yang tinggi dan biasa ditarik traktor empat roda
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