Retrogradation behavior of starch dough prepared from damaged cassava starch and its application in functional gluten-free noodles

Retrogradation-induced physicochemical changes in pre-cooked rice noodles stored at different temperatures: a viewpoint from water dynamics and structure

BACKGROUND

There has been significant interest in pre-cooked noodles that have a long shelf life and are convenient to cook. However, the thermal processes during preparation, and their high moisture content, can lead to significant quality deterioration during storage. Nevertheless, a comprehensive evaluation of these quality losses has not yet been conducted.

RESULTS

The effects of different storage temperatures (25, 4, and -20 °C) on the retrogradation-related physicochemical changes in pre-cooked rice noodles were elucidated mainly from the water dynamics and structural viewpoints. Thermal analysis demonstrated that amylopectin recrystallization took place in the noodles stored at refrigerated temperature, followed by room temperature. The refrigerated storage accelerated the starch retrogradation that caused the water molecules to become entrapped within the crystalline structure by lowering the water hydration properties and weighted T2 relaxation times of the pre-cooked noodles. These water mobility patterns were correlated with the textural changes in the noodles (greater hardness and Rmax /extensibility). Furthermore, the higher structural density and thickness derived from starch retrogradation were observed in the tomographic and microscopic images of the refrigerated noodles. The principal component analysis demonstrated that various physicochemical changes of the pre-cooked noodles during storage showed high correlations with the degree of starch retrogradation (r > 0.83).

CONCLUSION

The physicochemical features of the precooked noodles stored under refrigerated conditions were involved in the molecular dynamics of water, showing a notable water mobility reduction derived from the starch retrogradation, which contributed to their thermal, tomographical, and textural changes. © 2023 Society of Chemical Industry.

In Vitro Assessment of Ozone-Treated Deoxynivalenol by Measuring Cytotoxicity and Wheat Quality

Deoxynivalenol (DON), a trichothecene mycotoxin, could lead to cytotoxicity in both animal bodies and plant seed cells. Ozone degradation technology has been applied to DON control. However, the safety and quality of the contaminated grain after DON degradation are largely obscured. In this work, we evaluated the cytotoxicity of ozone-treated DON through seed germination experiments and cytotoxicity tests. Cell experiments showed that the inhibition rate of HepG2 viability gradually increased within the concentrations of 1-10 mg/L of DON, alongside which an IC50 (half maximal inhibitory concentration) of 9.1 mg/L was determined. In contrast, degrading DON had no significant inhibitory effect on cell growth. Moreover, a 1-10 mg/L concentration of DON increased production of a large amount of reactive oxygen radicals in HepG2, with obvious fluorescence color development. However, fluorescence intensity decreased after DON degradation. Further, DON at a concentration of >1 mg/L significantly inhibited the germination of mung bean seeds, whereas no significant inhibition of their germination or growth were observed if DON degraded. Changes in total protein content, fatty acid value, and starch content were insignificant in wheat samples suffering ozone degradation, compared to the untreated group. Lastly, the ozone-treated wheat samples exhibited higher tenacity and whiteness. Together, our study indicated that the toxicity of DON-contaminated wheat was significantly reduced after ozone degradation.

Ordered structural changes of retrograded instant rice noodles during the long-term storage

Temperature-induced textural, cooking properties and structural variations of retrograded instant rice noodles (IRN) during the long-term storage were systematically investigated. IRN samples stored at 4 °C exhibited a relative high cooking loss (2.45 %), and their hardness values gradually increased with prolonged storage. Moreover, the higher storage temperature (35 °C) accelerated the deterioration of IRN texture. Fresh IRN displayed a typical B-type XRD pattern with 9.65 % relative crystallinity (RC). During the initial 2 weeks of storage, the formation of a long-range ordered structure led to an increase in RC, which was closely related to the duration and temperature of storage (ranging from 4 °C to 25 °C to 35 °C). Over the 12-week storage period, there was likely a disorganization of the supra-molecular structure, as evidenced by the considerably decreased RC and reduced water mobility. Furthermore, Pearson's correlation analysis highlighted that the tight integration between starch molecules and water molecules endowed IRN samples with enhanced smoothness and tenderness in flavor profiles. Hence, the study is expected to provide a comprehensive understanding of the mechanisms underlying molecular order changes in retrograded starch gel products during the long-term storage.

Assessment of freeze damage in tuber starch with electrical impedance spectroscopy and thermodynamic, rheological, spectrographic techniques

In this study, we aimed to use electrical impedance spectroscopy (EIS) to assess the freeze-damage level of starches from potato tubers treated with multiple freezing-thawing (FT) cycles. The results showed that the relationship between the physicochemical properties of starches and the impedance characteristics of starch paste is temperature-dependent. As the temperature rises to 70-90 °C, the impedance modules show a significant correlation with the amylose and mineral contents, gelatinization and pasting properties, short-range ordered structure, relative crystallinity, and damage level within the range of 10-1 MHz (p < 0.01). This could be because FT leads to a reduction in amylose and ion content. Compared to a high level of freeze-damaged starch (FDS), a low level of FDS has less amylopectin and more amylose. Additionally, the ions could be typically evenly distributed throughout the unbranched linear amylose structure in starch paste. At the peak gelatinization temperature, the starch paste made from a low level of FDS exhibits a weakened network structure, allowing more unbound water for ion movement and enhancing electric conduction. In conclusion, EIS can predict the damage level and properties of FDS, which can benefit the frozen starchy food industry.