Pigmented sweet potatoes (SPs) are outstanding sources of anthocyanin, β-carotene and other color-related phytonutrients. However, fresh SP roots are highly perishable and difficult to store. To reduce losses and extend their uses, fresh SP could be converted into flour. SP cultivars with deep purple (Phichit 65-3) and orange-fleshed (T101) colors newly developed in Thailand were studied. The influence of drying methods on physico-chemical properties, anthocyanin, β-carotene and antioxidant activity retentions of purple and orange-fleshed SP flours (SPFs) was investigated. Peeled purple and orange SPs were pretreated by blanching (100°C, 5 sec) and soaking in 0.5 % (w/v) sodium metabisulphite, then dried in either hot air oven at 50-80°C or steamed for 10 min and placed to the drum dryer at 80-110°C and 3-7 rpm drum speed. The drying processes significantly enhanced anthocyanin contents of SPFs by 1.8 to 3.8 times; however, there was a significant loss of β-carotene occurred during drying processes. Drum drying yielded SPFs with better color, higher total phenolic contents and antioxidant activity than the hot air drying. Pasting temperatures of hot air dried orangefleshed SPFs (84-85°C) were slightly higher than those of purple-fleshed SPFs (80-83°C). Drum drying process produced pre-gelatinized (instant) SPFs as indicated by RVA and DSC results. The optimal conditions for drum dried and hot air dried SPF manufactured were 95°C at 5 rpm and 70°C, respectively, based on anthocyanin, β-carotene, total phenolic, antioxidant activity, color retentions, and pasting properties.
Terminalia catappa Linn (TC) is an ornamental tree planted extensively in many countries. It has been known for a long time that the seeds are edible but no research has focused on the realm of its use as food. Our previous data showed that the seed contains high levels of oil content (600 g/kg) and possesses the optimum fatty acid balance indicated in fat dietary guidelines. This study aims to investigate the physical and chemical properties and the possibility of using TC seed oil as a new dietary lipid. The effects of extraction conditions, partial refining process, and storage stability on TC oil properties were conducted compared with soybean oil. The results showed that physicochemical properties including the density, refractive index, melting point, acidity, free fatty acid, saponification value, unsaponifiable, peroxide, and fatty acid composition of the extracted oil were comparable with soybean oil and their values followed the dietary standard of edible oil.
Reactive extrusion (REX) was proposed as a means of modifying the functionalities of cassava starch through cross-linking using a pilot-scale, co-rotating twin screw extruder. Cassava starch was blended with sodium trimetaphosphate (STMP) and extruded at a constant feed rate of 5.3 kg/h, a reaction temperature of 40°C and a screw speed of 200 rpm. Response surface methodology was used to evaluate the effects of moisture content (50-85% of dry weight starch), NaOH concentration (0.05-0.1 M) and STMP level (0.5-2.0% of dry weight starch) on the degree of substitution (DS), degree of cross-linking, and pasting properties, as well as the water solubility index (WSI) and swelling power of cross-linked starch. Regression analysis showed that the DS of cross-linked cassava starch was affected significantly (p < 0.05) in linear terms, while the degree of cross-linking and pasting properties were affected significantly (p < 0.05) in linear, interaction, and quadratic terms. DS varied from 0.0038 to 0.0149 and increased as the moisture content decreased. Introduction of phosphate cross-links into the starch restricted the mobility of the molecular structure, leading to a reduction in WSI and viscosities of starch. Starch became slightly yellowish with an increase in NaOH concentration. Starches with a degree of cross-linking between 51 and 56% yielded the highest peak viscosity (2197-2448 cP), final viscosity (3185-3422 cP), and swelling power (8.03-8.45). Cross-linking reaction through REX altered the crystalline patterns of cassava starch. Cross-linked cassava starches with different degrees of cross-linking and functionalities were developed successfully using a pilot-scale REX, which could be utilized as food and non-food additives.
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