Effects of endogenous lysophospholipids on pasting and thermal behaviour of aged rice

Abstract

Lysophospholipids (LPLs) as major polar lipids in rice grains, have both importance in nutritional, cooking and storage quality. This study investigated the effects of endogenous lysophosphatidylcholine (LPC) and lysophosphatidylethanolamine (LPE) on pasting and thermal behaviours of rice artificially aged under different temperature (20, 30 and 40 °C) and relative humidity (RH, 50 and 95%) conditions. In aged paddy rice, the high storage temperature (40 °C) increased pasting characteristics. High RH (95%) slightly increased pasting temperature (PT) but reduced enthalpy of gelatinization (ΔHg). Starch LPC18:0, LPE18:0, LPE18:1, LPE18:2, total LPE and total LPL significantly correlated with cool paste viscosity (CPV), setback (SB) and consistency (CS), while starch LPE14:0 positively correlated with thermal properties (P < 0.05). Non-starch LPC14:0 and LPC18:2 negatively correlated SB and CS. In aged milled rice, high storage temperature (40 °C) and RH (95%) also significantly increased SB, CS and PT, while low RH (50%) resulted in higher peak viscosity (PV), hot paste viscosity (HPV), CPV, breakdown (BD) and ΔHg (P < 0.05). Starch LPC14:0, LPC18:0, LPE16:0, LPE18:0, LPE18:1, LPE18:2 and total LPE significantly correlated with pasting properties, but starch LPE14:0, LPE16:0 and LPE18:0 greatly correlated with thermal properties (P < 0.05). Except for non-starch LPC14:0, there were no significant relations between individual non-starch LPLs and physicochemical properties of aged milled rice. These findings suggested the important roles of endogenous non-starch and starch LPLs in controlling pasting and thermal behaviours of aged rice grains.