Abstract
Sea buckthorn is ranked among the most significant super foods worldwide. Its fruits and leaves are used as fresh or dried in food, pharmaceutical and cosmetic industry. As super food any pre-treatment should sustain this property and hence this research was focused on osmotic dehydration of sea buckthorn by stevia also a super food. Therefore, water loss, sugar gain, acidity, ascorbic acid and water diffusivity were evaluated during osmotic dehydration of sea buckthorn by two stevia solutions, 15ο and 30οBrix and following were air-dried at 50οC by comparing the effect of steam blanching per case. Steam blanched samples exhibited increased water loss at the end of the process, 55% at 30οBrix and 48% at 15οBrix, compared to untreated samples where losses were 43% (30οBrix) and 28% (15οBrix) respectively. Ascorbic acid was significantly reduced, exceeding 50% in steam blanched samples and 23% in untreated samples. Steam blanched samples dehydrated at 15oBrix exhibited 82% dry matter increase and only 39% the untreated samples. Similarly, samples dehydrated at 30oBrix exhibited 84% dry matter increase and 53% when no steam blanching was applied. Solid gain was seven times less compared to water loss which is attributed to high molecular weight of steviol glycoside. The osmotic dehydration and airdrying curves were described effectively by Peleg and Fick models, and Logarithmic and Fick models respectively, having in all cases R2 adj>99% and SEE<0.2. The water diffusivity of steam blanched samples was 3.2-5.57×10-11 m 2 /s for water loss and 1.27- 2.03×10-11 m 2 /s for solid gain at 30oBrix and 2.12-4.27×10-11 m 2 /s and 0.91-1.98×10-11 m 2 /s at 15oBrix. Finally, the water diffusivity of steam blanched samples during air-drying was 2.11-2.29×10-11 m 2 /s and 1.56-1.66×10-11 m 2 /s in the case of untreated samples.
Highlights
Sea buckthorn (Hippophaes rhamonides L) is among the most important superfoods and is used for its fruits as well its leaves
And b, it can be seen that solid gain is seven times smaller of water loss. This response can be attributed to the high molecular weight of steviol glycoside that favours water loss at the expense of solid gain as Mundada et al (2010) explained
Hawkes and Flink (1978) reported that the progressive accumulation of solids during the osmotic dehydration, form a surface layer on the external cellular layer of sea buckthorn, which acts as a barrier against water loss and solid gain
Summary
Sea buckthorn (Hippophaes rhamonides L) is among the most important superfoods and is used for its fruits as well its leaves. Sea buckthorn has many nutritional benefits as it has been reported to contain more than 190 essential compounds in seeds, pulp, fruit and juice, such as vitamins A, K, C, B1, B2 and E, fatty acids, lipids, organic acids, amino acids, carbohydrates, folic acid, tocopherols, flavonoids, phenols, terpenes and tannins which have beneficial effects on health (Bal et al, 2011). The pH of sea buckthorn juice ranges from 2.7 to 3.1 which do not favour ascorbate oxidase activation and ascorbic acid is largely retained during juice processing. The sea buckthorn juice is characterized by high quantities of various organic acids so its acidity ranges from 3.5 to 7.3% (Zeb, 2004)
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