Effects of natural freeze-thaw treatment on structural, functional, and rheological characteristics of starches isolated from three bitter potato cultivars from the Andean region

Impact of repeated freeze-thawing on the functional, molecular, rheological and thermal properties of isolated quinoa (Chenopodium quinoa Willd.) starch

This study was undertaken to understand the functionality of quinoa starch (QS) in frozen foods. The effects of different cycles of freeze-thaw treatment (0, 2, 4, 6, and 8 cycles) on the functional, molecular, rheological, and thermal characteristics of starch from quinoa seeds were investigated. The extraction yield of QS was 52 %, with a purity value of 97.98 %. The study observed amorphization of starch molecule after repeated FT, as it primarily affected the crystalline domains. Reduction in the oil absorption capacity (OAC) of starch from 115 % to 95 % was linked to increase in surface roughness, which was further corroborated by scanning electron microscopy and contact angle analysis. Further studies also revealed reduction in relative crystallinity from 36.21 % to 32.34 %, degree of ordered structure from 1.59 to 1.06, and gelatinization enthalpy from 19.99 J/g to 8.48 J/g, as indicated by X-ray diffraction (XRD), Fourier transform infrared (FTIR), and differential scanning calorimetry (DSC), respectively. All starch gels showed a pseudo-plastic behaviour (η < 1), which the power law model described well. Additionally, the gel-forming ability of starches improved as indicated by higher values of storage (G') and loss (G″) moduli. In conclusion, the number of freeze-thaw cycles significantly influences the various characteristics of QS.

Effect of Freezing Temperature on the Thermal, Rheological, and Gelatinization Properties of Freeze-Thaw-Dehydrated Potato Powder

To promote the application of freeze-thaw-dehydrated (FTD) potatoes and their gels, this study aimed to investigate the effects of freezing temperature on the physicochemical and gel properties of FTD potato powder and their correlation. The results revealed that, as the freezing temperature decreased, the solubility exhibited an overall downwards trend resulting from soluble solids and amylose liberation. Owing to the better cell integrity at -20 °C, the solubility was greater than that of the other treatment groups. In contrast, the trough viscosity and melting enthalpy increased, and the final viscosity, and setback first increased but then decreased. Regarding the properties of the FTD potato powder gel, the storage modulus, loss modulus, hardness, adhesiveness, chewiness, and consistency first increased but then decreased with decreasing freezing temperature. At a moderate freezing temperature (-20 °C), the solubility and stability of the FTD potato powder were well maintained, and the final viscosity, setback, and hardness reached their highest values. Correlation analysis revealed that, with decreasing freezing temperature, the amount of FTD potato powder initially increased, followed by a decrease in the final viscosity and setback. This trend was positively correlated with the hardness of the FTD potato gel (r = 0.98, r = 0.93).

Quality deterioration of mashed potatoes during the freeze-thaw cycle: From the perspective of moisture and microstructure

This study aimed to simulate cold chain sales temperatures to predict the effects of temperature fluctuations on the physicochemical properties, moisture distribution, microstructure, and flavor of mashed potatoes. The results showed a decline in the hardness and chewability of mashed potatoes alongside the migration of water from bound water states to weakly bound states under freeze-thaw cycles (FTC) conditions. Microstructural analysis indicated that the adhesive forces between proteins and starch granules were weakened, and the structure of mashed potatoes particles was destroyed following FTC. The oxidation and degradation of fat induced by FTC increased the content of key compounds such as octanal and nonanal, thereby contributing to an overall deterioration in the flavor of mashed potatoes. This study elucidates the effects of FTC on water migration, microstructure, and flavor characteristics of mashed potatoes, thereby providing a theoretical foundation for improving the quality of prefabricated frozen mashed potatoes dishes.

Physicochemical properties of starch of four varieties of native potatoes

The limited industrial use of indigenous varieties of native potatoes has caused a decrease in its cultivation, restricting it to the self-consumption of the Andean population. The present study analyzed the physicochemical, thermal, and structural properties of the starches extracted from four of these varieties Aq'hu Pukucho, Yurakk Kkachun Wakkachi, Yurac Anca, and Huarmi Mallco, as a potential source of be used in industries such as food, pharmaceutical and, bioplastics. The percentage yield in wet extraction ranged between 14.53 and 20.26 %. The luminosity L* and whiteness index (WI) values were observed in ranges of 90.75-92.71 and 90.05-91.50, respectively. The Finding revealed various techno-functional properties, since the level of amylose varied between 36.29 and 43.97 %, an average zeta potential of -22 mV, and a maximum viscosity between 19,450-14,583 cP. The starches showed consistent thermal behavior since the TGA curves showed three stages with gelatinization temperatures that ranged between 54.9 and 59.75 °C, an enthalpy of 3.60-6.62 J/g, and various shapes of particles such as circular, elliptical, and oval. In conclusion, the relationships between variables such as water absorption index, swelling power, viscosity, crystallinity, enthalpy, and gelatinization temperature reveal different characteristics of each type of starch, which can influence its use.

Impacts of transglutaminase on the processing and digestion characteristics of glutinous rice flour: Insight of the interactions between enzymic crossing-linked protein and starch

Glutinous rice is extensively consumed due to its nutritious content and wonderful flavor. However, glutinous rice flour has a high glycemic index, and the storage deterioration of sweet dumplingsissevere. Transglutaminase (TG) was used to cross-link glutinous rice protein and improve the characteristics of glutinous rice products. The findings demonstrated that TG significantly catalysed protein cross-linking to form a dense protein network, reduced the viscosity of glutinous rice paste and improved the thermal stability. The protein network may physically block the access of starch granules to digestive enzymes to lower the digestion rate of starch, and attenuate the damage of ice crystal molecules to the starch structure to improve the freezing stability of starch gels. The cracking rate and water loss of sweet dumplings prepared using glutinous rice flour with TG treated for 60 min reduced significantly. In conclusion, this study broadened the application of TG in starch products.

Characterization of Nano- and Microstructures of Native Potato Starch as Affected by Physical, Chemical, and Biological Treatments

Modifying starch allows for improvements in its properties to enable improved uses in food matrices, bioplastics, and encapsulating agents. In this research, four varieties of native potato starch were modified by acid treatment, enzymatic treatment, and ethanol precipitation, and their physicochemical, structural, thermal, and techno-functional characteristics were analyzed. According to FT-IR analysis, no influence of the modified starches on the chemical groups was observed, and by scanning electron microscopy (SEM), spherical and oval shapes were observed in the acid and enzymatic treatments, with particle sizes between 27 and 36 μm. In particular, the ethanolic precipitation treatment yielded a different morphology with a particle size between 10.9 and 476.3 nm, resulting in a significant decrease in gelatinization temperature (DSC) and more pronounced crystallites (XRD). On the other hand, the enzymatic treatment showed higher values for z-potential (ζ), and the acid treatment showed lower mass loss (TGA). Acid and ethanolic treatments affected the dough properties compared to native starches. The techno-functional properties showed a decrease in the water absorption index, an increase in the water solubility index, and varied swelling power behaviors. In conclusion, the modification of potato starches through acid, enzymatic, and ethanolic precipitation treatments alters their physicochemical properties, such as swelling capacity, viscosity, and thermal stability. This in turn affects their molecular structure, modifying morphology and the ability to form gels, which expands their applications in the food industry to improve textures, stabilize emulsions, and thicken products. Furthermore, these modifications also open new opportunities for the development of bioplastics by improving the biodegradability and mechanical properties of starch-based plastic materials.

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.

Static magnetic field improvement of the quality of rice dumpling subjected to freeze-thaw cycles: Roles of phase transition of water and changes in structural and physicochemical properties of glutinous rice flour

This study aimed to investigate the effect of static magnetic field (SMF, 0-10 mT) on the quality of rice dumplings subjected to 7, 14, 21, and 28 freeze-thaw cycles. The underlying mechanism was explored by monitoring changes in water phase transition, water distribution, and structural and physicochemical properties of rice flour. Results suggested that SMF enables the formation of small ice crystals by accelerating freezing rate, shortening phase transition time, and increasing bound water content, which attributes to reducing the mechanical damage on starch granules and thus improves the quality of frozen rice dumpling. After 7-28 freeze-thaw cycles, SMF treatment increased the whiteness by 0.08-1.58, reduced the cracking ratio by 1.67 %-8.34 %, decreased the water loss ratio by 0-0.75 %, and significantly improved the texture of cooked rice dumplings. This study confirmed the feasibility of SMF in improving the quality of rice dumpling, which contributes to expanding the applications of magnetic freezer in the preservation of starch-based foods.