Garlic essential oil emulsions stabilized by microwave dry-heating induced protein-pectin conjugates and their application in controlling nitrite content in prepared vegetable dishes

The main objective of this study was to assess whether microwave dry-heating (MDH) can shorten the conjugation time and achieve similar level of glycosylation between soy protein isolate (SPI) and citrus pectin (CP) obtained using traditional dry-heating (TDH). It also involved the application of SPI-CP conjugates produced by MDH (SPI-CP-MDH) as an emulsifier of garlic essential oil (GEO) emulsions and used these emulsions to control nitrite content of prepared vegetable dishes (PVDs). At a power density of 1.5 W/g, MDH shortened the conjugation time by 25% and achieved higher glycosylation degree, compared to TDH. SPI-CP-MDH conjugates exhibited comparable emulsifying and emulsion stabilizing characteristics on GEO emulsions, compared with SPI-CP-TDH conjugates. The ability of SPI-CP-MDH conjugates to inhibit the formation of nitrite in PVDs was higher than that of SPI-CP-TDH conjugates. The control of nitrite formation was attributable to the inhibition of nitrite-producing bacteria through antioxidant and anti-light properties of emulsions rather than reducing enzyme activity associated with nitrite in plant cells. MDH can be an alternative to TDH for producing SPI-CP conjugates. GEO emulsions stabilized by SPI-CP-MDH conjugates can potentially be a preferred option to control nitrite content in PVDs.