| 1. |
- Guiamba, Isabel, 1963, et al.
(författare)
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Effect of Infrared Blanching on Enzyme Activity and Retention of β-Carotene and Vitamin C in Dried Mango
- 2015
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Ingår i: Journal of Food Science. - : Wiley. - 0022-1147 .- 1750-3841. ; 80:6, s. E1235-E1242
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Tidskriftsartikel (refereegranskat)abstract
- The objectives of this work were to evaluate infrared (IR) dry blanching in comparison with conventional water blanching prior to hot air drying of mango to inactivate polyphenol oxidase (PPO) and ascorbic acid oxidase (AAO) enzymes, and to study its effect on color change and retention of vitamin C and β‐carotene. Mango cylinders were blanched under similar temperature–time conditions either by IR heating or by immersion in a water bath during 2 min at 90 °C (high‐temperature‐short‐time—HTST) or for 10 min at 65 °C (low‐temperature‐long‐time—LTLT). After blanching mango was hot air dried at 70 °C. PPO was completely inactivated during the blanching treatments, but AAO had a moderate remaining activity after LTLT treatment (∼30%) and a low remaining activity after HTST treatment (9% to 15%). A higher retention of vitamin C was observed in mango subjected to IR dry blanching, 88.3 ± 1.0% (HTST) and 69.2 ± 2.9% (LTLT), compared with water blanching, 61.4 ± 5.3% (HTST) and 50.7 ± 9.6% (LTLT). All‐trans‐β‐carotene retention was significantly higher in water blanched dried mango, 93.2 ± 5.2% (LTLT) and 91.4 ± 5.1% (HTST), compared with IR dry blanched, 73.6 ± 3.6% (LTLT) and 76.9 ± 2.9% (HTST). Increased levels of 13‐cis‐β‐carotene isomer were detected only in IR dry blanched mango, and the corresponding dried mango also had a slightly darker color. IR blanching of mango prior to drying can improve the retention of vitamin C, but not the retention of carotenoids, which showed to be more dependent on the temperature than the blanching process. A reduction of drying time was observed in LTLT IR‐blanching mango.
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| 2. |
- Guiamba, Isabel, 1963, et al.
(författare)
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Effects of blanching, acidification, or addition of EDTA on vitamin C and β-carotene stability during mango purée preparation
- 2016
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Ingår i: Food Science and Nutrition. - : Wiley. - 2048-7177. ; 4:5, s. 706-715
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Tidskriftsartikel (refereegranskat)abstract
- The impact of acidification with citric acid, addition of EDTA or water blanching at high temperature, and short time (HTST) conducted at 90°C for 4 min, on the retention of vitamin C (L-AA and DHAA) and β-carotene was studied in mango purée 30 min after crushing. HTST blanching prior to matrix disruption into purée resulted in complete inactivation of polyphenol oxidase (PPO) and minor residual activity (8%) of ascorbic acid oxidase (AAO). The retention of total vitamin C was 100% in blanched purées and in purée with EDTA and about 90% in purées at pH 3.9 and 5.0. Acidification, blanching, and addition of EDTA preserved vitamin C mainly as L-AA, while complete conversion into DHAA was observed in purée at pH 5.0. The retention of all-trans-?-carotene was between 65 and 72%, with the highest value in purée with EDTA and the lowest value in purée of blanched mango. The ratio of 13-cis-β-carotene in fresh mango was 8.2 ± 0.5% that increased significantly after blanching and in purée at pH 5.0.
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| 3. |
- Guiamba, Isabel, 1963, et al.
(författare)
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Enhancing the retention of β-carotene and vitamin C in dried mango using alternative blanching processes.
- 2018
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Ingår i: African Journal of Food Science. - 1996-0794. ; 12:7, s. 165-174
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Tidskriftsartikel (refereegranskat)abstract
- The effects of microwave (MW) dry blanching of mango in comparison with conventional water blanching and blanching in closed plastic bags prior to hot air drying (70°C) were evaluated on the retention of vitamin C and β-carotene and on the activity of polyphenol oxidase (PPO) and ascorbic acid oxidase (AAO) enzymes. Blanching conditions for MW and water blanching were 2 min at 90°C high temperature and short time (HTST) or for 10 min at 70°C low temperature and low time (LTLT). PPO was completely inactivated by the blanching treatments, while low AAO activity remained. High retentions (~100%) of vitamin C were found in dried mango after blanching treatments HTST with MW and blanching in closed plastic bags, while lower retention was observed after LTLT with MW (81.8 ± 4.5%), and conventional water blanching 86.7 ± 2.6% (HTST) and 78.6 ± 2.5% (LTLT). Blanching resulted in partial oxidation of L-AA into dehydroascorbic acid (DHAA). Lower retention of all-trans-β-carotene was obtained in MW and HTST water blanched dried mango (82 to 90%) compared with LTLT water blanched dried mango (~100%). In all dried blanched mango samples the levels of 13-cis-β-carotene isomer increased. A slight darkening of colour was observed only in conventional blanched mango samples.
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| 4. |
- Guiamba, Isabel, 1963
(författare)
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Nutritional Value and Quality of Processed Mango Fruits
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Mango (Mangifera indica L.) is one of the most important tropical fruits commercialized and consumed worldwide, and an excellent source of fibre, bioactive compounds such as pro-vitamin A carotenoids, vitamin C (ascorbic acid) and phenolics. Mango was used in this thesis as a model fruit of fruits and vegetables that are rich sources of nutrients. They are highly perishable, prone to progressive undesired changes if stored untreated. As a result, large amounts of mango are lost annually in many areas of the world including Mozambique. To reduce postharvest losses of fruits, processing is recommended since it extends the shelf life and enable the availability off-season, and the promotion of consumption is a potential health enhancing strategy. However, processing of fruits and vegetables must be carefully designed to achieve a high sensory and nutritional quality of the final products. The aim of the present thesis was thus to evaluate the effect of conventional and novel processing techniques on the retention of vitamin C and β-carotene, two major bioactive compounds, in minimally processed or dried mango products.The effect of osmotic dehydration (OD) with or without vitamin C or calcium prior to hot air-drying was evaluated in terms of the retention of vitamin C and β-carotene in dried mango. Fortification of OD solutions with either calcium or vitamin C was shown to be an efficient way to improve the retention of vitamin C and carotenoids in dried mango. OD pre-treatment reduced the hardness, drying time, and prevented colour changes. The potential use of alternative blanching techniques to improve the retention of vitamin C and β-carotene in processed mango was explored using infrared (IR) and microwave (MW) dry blanching and blanching in a closed plastic bag immersed in water bath at (High-Temperature-Short-Time - HTST) or (Low-Temperature-Long-Time - LTLT), prior to hot air-drying. Complete inactivation of PPO was achieved, while a minor activity of AAO remained. An improved retention of vitamin C in dried mango was achieved using IR and MW dry blanching or water blanching in plastic bag in comparison to conventional water blanching. However, the retention of all-trans-β-carotene was higher in dried mango after water blanching than after dry blanching. In conclusion, a correct selection of suitable techniques and conditions for blanching can enhance the nutritional value of dried mango and inactivate enzymes that degrade vitamin C and β-carotene.To address the problem of reduced sensory and nutritional quality during the processing of purées, the impact of acidification, addition of EDTA or water blanching at HTST, on the retention of vitamin C (L-AA and DHAA) and β-carotene was evaluated in mango purée. The results showed that the disruption of the cellular matrix during purée processing facilitates oxidative reactions of vitamin C and of all-trans-β-carotene unless protected by an initial blanching step, pH adjustments or addition of EDTA a chelating agent to inhibit AAO and PPO activities.
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| 5. |
- Guiamba, Isabel, 1963, et al.
(författare)
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Retention of beta-carotene and vitamin C in dried mango osmotically pretreated with osmotic solutions containing calcium or ascorbic acid
- 2016
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Ingår i: Food and Bioproducts Processing: Transactions of the Institution of of Chemical Engineers, Part C. - : Elsevier BV. - 1744-3571 .- 0960-3085. ; 98, s. 320-326
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Tidskriftsartikel (refereegranskat)abstract
- The retention of vitamin C and carotenoids was studied in the cv. 'Tommy Atkins' mango as affected by osmotic dehydration prior to hot air drying. Osmotic dehydration (OD) was carried out over 15 h at 25°C using sucrose solutions of 45°BRIX with and without 1% (w/w) calcium chloride or 1% ascorbic acid with a fruit to solution ratio of 1:10 (w/w), and the OD-treated mango samples were then dried in an air convection oven at 50°C or 70°C. An osmotic pretreatment before drying significantly reduced the drying time and prevented colour change in dried mango. Addition of calcium in the OD solution significantly improved vitamin C retention, on average from 44% to 57%. However, the addition of ascorbic acid to the osmotic solution highly increased the retention of vitamin C content in the dried mango. The retention of all-trans-β-carotene was significantly lower in all OD treated mango samples dried at 50°C but remained unchanged in OD-treated mango samples with calcium or vitamin C dried at 70°C. Moreover, osmotic dehydration with and without additives reduced the ratio of 13-cis-β-carotene to all-trans-β-carotene. The results showed that the addition of calcium or vitamin C to the osmotic solution can improve the nutritional value of dried mango.
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