Effect of Intermittent Low-Pressure Radiofrequency Helium Cold Plasma Treatments on Rice Gelatinization, Fatty Acid, and Hygroscopicity

Abstract

To establish the safe and reproducible effects of cold plasma (CP) technology on food products, this study evaluated the gelatinization parameters, fatty acid profile, and hygroscopic properties of rice grains repeatedly treated with low-pressure radiofrequency (RF) helium CP (13.56 MHz, 140 Pa, 120 W-20s, 0–4 times, and 300 g sample). Compared with the untreated (zero times) sample, with an increase in CP treatment times from one to four on rice, the water contact angle and cooking time decreased, while the water absorption rate and freshness index increased, and the pH value remained unchanged. CP repeating treatments essentially had no effect on the gelatinization enthalpy, but significantly increased the peak temperature of gelatinization. From the pasting profile of rice that has been repeatedly CP treated, the peak, breakdown, and setback viscosities in flour paste decreased. CP repeating treatments on rice did not change the short-range molecular order of starch. Compared with the untreated sample, the first helium CP treatment maintained the content of C18:1n9c, C18:2n6c, and C18:3n3, but the second to fourth CP treatment significantly decreased contents of these fatty acids (FAs) as the C18:0 content increased. The first three CP treatments can increase the water and sucrose solvent retention capacity in rice flours. CP repeatedly treated rice first exhibits the similar monolayer water content and solid surface area of water sorption. Principal component analysis shows that contact angle, pasting parameters, and fatty acid profile in milled rice are quite sensitive to CP treatment. Results support that the effect of low-pressure RF 120W helium CP treatment 20 s on rice grains is perdurable, and the improvement of CP intermittent treatments on rice cooking and pasting properties is an added benefit, and the hygroscopic properties of rice was kept.

Study of the Gelatinization, Fatty Acid Profiles and the Conversion of Ergosterol into Vitamin D in Wheat Shorts by Optimization of Low-pressure Radiofrequency Cold Plasma Treatment Conditions

“…When they were treated by 120W lowpressure RF oxygen or helium CP, all CP treatments for 30-180s steadily degraded the ERG, and most treatments could convert ERG into VD 2 or VD 3 -like compounds, with the 90-120s treatments showing the greatest effect. To our knowledge, this result is the first observed effect of cold plasma on cereals, maybe due to the meta-stable helium atoms and high-energy photons generated from lowpressure RF helium CP [31] and high concentration of oxygen ion from oxygen CP [32] .…”

Insights into Cold Plasma Treatment on the Cereal and Legume Proteins Modification: Principle, Mechanism, and Application

“…Similarly, Buβler et al [85] reported a decrease in pH from 7.0 to 4.0 when treating pea protein dispersions with CP at 8.8 kVpp for 10 min. The researchers attributed this pH change during plasma treatment to several factors: (a) the presence of reactive species in plasma, including ROS, RNS, and free radicals, directly or indirectly facilitating protein oxidation and generating acidic byproducts [86]; (b) nitrogen oxides, produced by the reaction of air under electric fields, combining with water forming nitrous (HNO 2 ) and nitric acid (HNO 3 ), contributing to acidity [87]; (c) bombardment by high-energy electrons or ions producing acidic entities such as hydronium ions (H 3 O + ), further altering sample pH [88]. These physicochemical reactions induce changes in the treated sample's pH, influencing protein behavior.…”