Abstract
The demand for vegetable powder has been escalating considerably due to its various health benefits and higher shelf life compared to fresh green leafy vegetables. Thus, much research emphasised manufacturing vegetable powder at a lower operational cost and higher efficiency while preserving the nutritive values of the vegetables. In this study, zinc- (Zn-) amaranth puree was liquefied with three types of cell wall degrading enzymes (i.e., Viscozyme L, Pectinex Ultra SP-L, and Rapidase PAC) with varying concentrations (0–3% v/w) and incubation time (0.5–24 h) at pH 5 and 45°C before the drying process. The results showed that enzymatic liquefaction using 1% (v/w) of Viscozyme L for 3 h was the optimal procedure for the reduction of the viscosity of the puree. The liquefied puree was then microencapsulated through either spray- or freeze-drying with different wall materials, e.g., 10% of maltodextrin (MD) DE 10, resistant maltodextrin (RMD), N-octenyl succinate anhydride (OSA) starches from waxy maize, HI CAP 100 (HICAP), Capsul (CAP), and gum Arabic (GA). The results showed that all freeze-dried powders generally had higher process yield (except for that encapsulated by HICAP), higher moisture content (but similar water activities), higher retention of total Zn-chlorophyll derivatives, lower hygroscopicity with slab-like particles, larger particle size, and lower bulk density than those of spray-dried powders. In contrast, the spray-dried powders exhibited irregular spherical shapes with relatively high encapsulation efficiency and antioxidant activities. Nonetheless, encapsulation using different wall materials and drying methods had no significant effect on the powder's cohesiveness and flowability.
Highlights
Green amaranth or Chinese spinach (Amaranthus viridis), commonly known as bayam hijau or bayam panjang in Malay, is one of the most popular leafy vegetables consumed in Malaysia
The viscosity of the puree can be regulated by adding water, a study by Chong and Wong [43] reported that liquefaction using enzymes with cellulolytic, hemicellulolytic, and pectinolytic activities is a better method, as the former could result in higher energy consumption for the removal of the additional water during spray-drying [9]
This finding is consistent with that of Stoll et al [47], which stated that carrot liquefaction was the most effective when using a mixture of enzymes with cellulolytic, pectinolytic, and hemicellulolytic activities, as seen from a drastic reduction of viscosity to 21% of the initial value within 90 min at 50°C
Summary
Green amaranth or Chinese spinach (Amaranthus viridis), commonly known as bayam hijau or bayam panjang in Malay, is one of the most popular leafy vegetables consumed in Malaysia. International Journal of Food Science or light [3, 4] Thereupon, to surpass these adverse conditions, the formation of stable chlorophyll molecules in green amaranth was initiated by substituting magnesium ion (Mg) with Zn in the porphyrin ring of Mg-free chlorophyll derivatives, such as pyropheophytins or pheophytin [6]. This approach allows the Zn-chlorophyll derivatives to have a similar colour to Mg-chlorophyll while being more stable and thermally resistant in low-pH food [7]
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