Effect of Infrared Blanching on Enzyme Activity and Retention of β‐Carotene and Vitamin C in Dried Mango

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.

Effects of blanching, acidification, or addition of EDTA on vitamin C and β‐carotene stability during mango purée preparation

“…Similar inhibition of AAO activity in mango of the Tommy Atkins cultivar (8% of the initial activity retained) was achieved after IR blanching at 90°C for 2 min (Guiamba et al. ). Cardello et al.…”

“…The PPO activity in the fresh mango was 121.6 ± 26.4 units, assuming no interference with the presence of vitamin C in the analysis as was shown by Ndiaye et al (2009). High losses of PPO activity (98%) have been reported in mango pulp after blanching in 5 min at 80°C (Wang et al 2007), and complete inactivation after 1 min of holding time at temperature levels between 85 and 93°C (Vásquez-Caicedo et al 2007) and after 2 min blanching at 90°C (Guiamba et al 2015). The pH optimum for PPO of the mango cultivar Haden has been reported to be between 5.6 and 6.0 (Park et al 1980), with only about 10% of the activity remaining at pH 4.…”

“…Significantly lower vitamin C retention (~60%) has recently been shown in HTST‐treated mango without plastic bag protection (Guiamba et al. ).…”

“…) and after 2 min blanching at 90°C (Guiamba et al. ). The pH optimum for PPO of the mango cultivar Haden has been reported to be between 5.6 and 6.0 (Park et al.…”

“…Few studies on the effect of AAO during plant food processing are found in the literature (Yamaguchi et al 2003;Munyaka et al 2010b;Leong and Oey 2012;Guiamba et al 2015). Munyaka et al (2010b) studied the stability of vitamin C (L-AA and DHAA) and AAO in crushed broccoli as influenced by different pretreatments.…”