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Effects of steaming and drying on quality and antioxidant activity of white-fleshed sweet potato powder (Ipomoea batatas)
(2024-01-01)
Thuy, N. M.
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Giau, T. N.
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Hao, H. V.
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Dung, N. C.
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Tai, N. V.
White-fleshed sweet potatoes (WFSP) are rich sources of polyphenols. The flesh of PFSP contains total polyphenol content (TPC) at 1.52 mgGAE/g fresh weight. The raw material’s total free radical scavenging capacity was estimated (at 42.4% DPPH). The inactivation of peroxidase (POD) and polyphenol oxidase (PPO), the breakdown of total phenolic compounds, antioxidant activity, and the whiteness of WFSP were evaluated during steam blanching from 0 to 9 minutes. Steam blanching time from 7 to 9 minutes at boiling temperature (100ºC) inactivated most of the POD and PPO enzymes (71.2% and 70.5%, respectively), thus TPC and antioxidant activity remains high, resulting in a bright white product. After 7 minutes of blanching, drying experiments of WFSP slices were conducted at air temperatures of 50 to 80ºC. The best alternative for describing and understanding the drying of WFSP slices was the Page model. In the temperature’s ranges, the values of the moisture diffusivity (De f f) and activation energy are obtained from 3.059×10−12 to 5.095×10−12 m2 /s and 14.93 kJ/mol, respectively. The drying temperature of 70ºC for 10 hours was suitable for producing WFSP powder with low water activity (0.5) and moisture content (6.5%), high TPC and antioxidant activity, and low specific energy consumption. These results suggested that the WFSP powder exhibited potential as a nutraceutical ingredient product.
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Effect of steamed purple sweet potato addition on chemico-physical properties of sandwich bread
(2023-12-01)
Thuy, N. M.
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Tham, T. T.H.
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Giau, T. N.
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Tien, V. Q.
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Thanh, N. V.
Purple sweet potato (PSP) has the potential to be used to prepare functional foods due to its attractive color and high anthocyanin content. With completely randomized design experiments used, the study investigated the effect of the percentage of steamed PSP (25, 29, 33 and 37% of total batch weight) on the overall quality of sandwich bread. The results showed that the added PSP significantly affected the color (L*, a* and b*) and anthocyanin content of bread. The sandwich bread with 33% PSP had the most intense purple color, and a soft structure was found with a measured hardness of 92.12 and 25.11 g force in the bread crust and the centre of the bread, respectively. The expansion ratio was 5.86 times compared with the control sample (5.47 times), and the moisture and anthocyanin content were 38.23% and 55.14 mg%, respectively. The findings of this study also suggested that the preparation of sandwiches with the addition of PSP, in addition to providing a beautiful color, also has the potential to improve overall product quality, increase fiber content (2.4%) and DPPH free radical scavenging activity (28.80%) compared to the control sample.
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Mathematical modelling of roselle seeds (Hibiscus sabdariffa L.) drying kinetics
(2023-08-01)
Thuy, N. M.
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Tram, N. B.
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Cuong, D. G.
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An, L. T.
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Duy, H. K.
Roselle seeds (Hisbiscus sabdariffa L.) are among the seeds that are high in nutrients and can be useful in several applications. Through the drying process, the seeds can be preserved for a long time. The roselle seeds were oven-dried at different temperatures 55, 60, 65 and 70°C, giving different outlet values for yield and final moisture. A total of five empirical mathematical models (Newton, Henderson and Pabis, Logarithmic, Diffusion approach and Page) were selected to describe and compare the drying characteristics of roselle seeds at respective drying temperatures. The adequately suitable drying temperature was found to be 70°C with a drying time of 4 hrs. The effective moisture diffusivity was calculated using the Fick diffusion equation. The results showed that the moisture content of the seeds gradually decreased with time. The effective diffusivity coefficient of moisture transfer varied from 5.4262×10-10 to 1.074×10-9 m2/s over the temperature range investigated. Mathematical models were fitted to the experimental data and by statistical comparison, the Page model represented drying characteristics better than the other equations with the highest R2 (0.998) and the lowest values of χ2 (0.00033) and RMSE (0.00023) observed for drying air temperature of 70°C. The dependence of moisture diffusivity on temperature was described by the Arrhenius equation, with the estimated activation energy being 43.08 kJ/mol within 55 to 70°C. Based on the selected model, it is possible to predict the moisture change during the drying of roselle seeds and thereby better control the process.
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Drying kinetics and mathematical modeling of dried macaroni supplemented with Gac aril
(2023-01-01)
Thuy, N. M.
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Giau, T. N.
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Tai, N. V.
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Minh, V. Q.
Macaroni is dried after being boiled to maintain their quality and extend their shelf life. Evaluation of moisture and nutrient changes aims to provide an overview of the phenomena occurring during the drying process. Thin layer drying kinetics of macaroni supplemented with Gac aril in hot air drying was investigated for temperatures range of 60 to 90ºC with six theoretical models were evaluated. It was observed that the Logarithmic equation gave the best prediction to the drying kinetics evidenced by high coefficient of determination (R2 ranging from 0.98-0.99). The lowest RMSE (0.0103 to 0.0426) and χ2 values (0.0002 to 0.0024) were obtained from the Logarithmic model within the defined temperature range. Diffusivity coefficients of moisture transfer were found ranging from 1.64×10−12 to 2.31 ×10−12 m2s−1 with activation energy was determined at 11.81 kJ.mol−1. Drying at 80ºC for 9 hours was selected for this product, the degradation kinetics of β-carotene and lycopene in macaroni followed a first-order kinetic model with half-life values were determined.
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Replacing a part of wheat flour with starchy food containing high levels of resistant starch in noodles processing
(2022-06-01)
Vuong, K. M.
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Tram, N. B.
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Tuyen, L. N.
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Vy, L. T.T.
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Tai, N. V.
Resistant starch has been shown to be associated with many health benefits. The study was conducted to analyze amylose and resistant starch content in selected starchy materials (black beans, red beans, green Xiem bananas, and potatoes) and investigate the influence of their flour/starch mixing ratio on the quality of noodles. The microstructure of noodles was analyzed by scanning electron microscopy. The results showed that potato starch had the highest resistant starch content (56.70%), followed by green Xiem banana flour (41.55%), black bean flour (16.51%), and red bean flour (15.55%). The raw materials with higher resistant starch also had higher amylose content. Amylose content, resistant starch content, and hardness of noodles increased when partly replacing wheat flour with the high level of RS flours/starches in the formulation. The data rank some tests revealed that formula A3 (replacing 50% of wheat flour with other starchy food containing high levels of resistant starch) was chosen due to the product containing relatively high RS content (14.78%), well structured and well accepted by panellists. The texture of the cooked noodles was assessed to be similar to that of the control sample (100% wheat flour). This study proved that it is possible to elaborate noodles to replace a part of wheat flour with starchy food containing high levels of the well-accepted formulation.

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