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Abstract The main aim of this work is to produce foam rubber using the Dunlop process from in-house creamed latex and compare it with commercial centrifuged latex. The dry rubber content of creamed latex is higher than that of fresh natural latex and traditional centrifuged latex. The creaming agent plays a major role during the preparation of foam rubber and therefore defines the density as well as the elastic and mechanical properties of the final product. Scanning electron microscopy images show lower porosity in rubber foam made from creamed latex compared to that from centrifuged latex. This methodology should have a highly positive impact on the rubber community in both upstream and downstream rubber industries.

Xanthone compounds in mangosteen (Garcinia mangostana Linn.) fruit have been reported to have biological activities including antioxidative and anti-inflammatory effects, and the major xanthone compounds in mangosteen are α-mangostin and γ-mangostin. The objectives of this research were to quantify and qualify the major xanthones in each part of the mangosteen fruit with and without yellow gum from the point of view of effective utilization of agricultural product. Quantitative evaluation revealed that yellow gum had extremely high amounts of α-mangostin and γ-mangostin (382.2 and 144.9 mg/g on a wet basis, respectively) followed by pericarp and aril. In mangosteen fruit with yellow gum inside, xanthones seemed to have shifted from the pericarp and to have concentrated in a gum on the surface of aril, and there was almost no difference between the amounts of α-mangostin and γ-mangostin in whole fruits with and without yellow gum. Pericarp and yellow gum showed much higher radical-scavenging activity and ferric reducing antioxidant potential than the aril.

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Anthocyanins are compounds extracted from natural origins, and can be use as a natural colorant. The high anthocyanin corn hybrid Kasetsart Purple Corn Single Cross (KPSC) 901 (Zea mays L.) is a new purple corn single cross-hybrid in Thailand. Anthocyanin extraction from KPSC 901 purple corn cob by new extraction methods, including microwave-assisted, ultrasound-assisted and ohmic heating techniques were studied and compared with the conventional heating method (solid : liquid ratio = 1:20) to select the best method for upscaling extraction. The extract was later concentrated and freeze-dried before quantity analysis. The optimal process for anthocyanin extraction was microwave-assisted extraction which gave a total anthocyanin content (TAC) of 397.1 mg/100 g corn cob powder. The extract powder had TAC and total phenolics content values of 3,446 and 20,915 mg/100 g powder, respectively. PRACTICAL APPLICATIONSIn this research, microwave-assisted extraction is the optimized method, which can help to efficiently extract anthocyanins and phenolic compounds from purple corn cob by using only water as a solvent for producing colorant powder. The powder dissolved in water and had a deep red color so it could be used in functional foods as a natural colorant and/or a source of active ingredients, depending on the concentration used.

Natural rubber (NR) is sensitive to oxidative degradation, which needs to add commercial antioxidant for NR compounding to improve its aging properties.The aim of this study is to apply natural antioxidant obtained from extracted rambutan peel powder (RE) by methanol compared to commercial antioxidants for NR compounding in a conventional vulcanization (CV system). Two types of commercial antioxidants were N-(1,3-dimethylbutyl)-N'phenyl-pphenylenediamine (6PPD) and 2,2,4-Trimethyl-1,2dihydroquinoline (TMQ).The main phenolic compounds in RE were geraniin, corilagin, ellagic acid and gallic acid which had greater antioxidant activity based on all methods, especially for 2,2-Diphenyl-2-picrlhydrazyl radical-scavenging assay (DPPH) and had a similar antioxidant activity to 6PPD. The antioxidants were applied in NR vulcanizates at 1 phr and 2 phr to study their physical and mechanical properties. The decomposition temperature of RE was higher than for 6PPD but similar to TMQ. The decomposition temperature of the rubber vulcanizates containing RE was higher than for the commercial antioxidants. Rubber vulcanizates with RE retained similar tensile strength and modulus at 100% strain as the commercial antioxidants. Furthermore, the addition of RE in rubber vulcanizates helped to resist thermal aging at 70 C and ozone aging, particularly at 1 phr at least as well as in the commercial antioxidants. Therefore, RE can be used as an alternative natural antioxidant in natural rubber to replace commercial antioxidants.