Lotus (Nelumbo nucifera G.) seeds are rich in nutrients and mainly used for food and medicinal applications. The seeds are an important food item in many countries and are generally considered a low glycemic index food. Starch is a major component of lotus seeds and may amount to over 50% of the dry weight. The quality of lotus seed products is mainly determined their starch properties, such as gelatinization and retrogradation. This review comprehensively summarizes recent developments in isolation, modifications, and applications of lotus seed starch (LS). This survey highlights different properties of native and modified LS in comparison with other starches. Native LS has been found with high amylose content (20-35%), high peak gelatinization temperatures (>70 °C), and pasting temperatures (>75 °C). The high amylose content has contributed to lower swelling power and fast retrogradation of LS. The modification of LS has been done using different methods, including thermal, microwave, high pressure, chemical, and enzymatic processing for functionality improvement. Native and modified LS have promising potential to be a valuable functional ingredient in different food and other applications. Finally, an outlook on the future possibilities for utilization of LS is provided.
Lotus seed starch was cross-linked using sodium trimetaphosphate (STMP) in varying amounts (1, 3, and 5%), and its rheological, pasting, thermal, and physicochemical properties were investigated. These cross-linked lotus seed starches (CL-LS-1, CL-LS-3, CL-LS-5) were also used to produce films (CL-LSFs), which were then examined for their mechanical characteristics, water vapor permeability, moisture content, opacity, thickness, and water solubility. After cross-linking, the solubility, amylose content, and swelling power of all the starch samples decreased. Cross-linking resulted in an increased pasting temperature, while peak viscosity (PV) decreased, with CL-LS-5 exhibiting the lowest peak viscosity (1640.22 MPa·s). In comparison to native starch, the thermal characteristics of CL-LS demonstrated greater gelatinization temperatures (To, Tp, Tc) and gelatinization enthalpy (ΔHgel). The gelatinization enthalpy of CL-LS varied between 152.70 and 214.16 J/g, while for native LS the value was 177.91 J/g. Lower moisture content, water solubility, and water vapor permeability were observed in the CL-LSFs. However, the cross-linking modification did not produce much effect on the film thickness. The highest tensile strength (12.52 MPa) and lowest elongation at break (26.11%) were found in CL-LSF-5. Thus, the starch films’ barrier and mechanical qualities were enhanced by cross-linking.
A comparative study between two novel starch modification technologies, i.e., microwave (MI) and γ-irradiation (IR), is of important significance for their applications. The objective of this work is to compare the changes in lotus rhizome starch (LRS) subjected to single modifications by MI (thermal treatment) and IR (non-thermal treatment), and dual modification by changing the treatment sequence, i.e., microwave followed by irradiation (MI-IR) and irradiation followed by microwave (IR-MI). The amylose content of native and modified LRS varied from 14.68 to 18.94%, the highest and lowest values found for native and MI-LRS, respectively. IR-treated LRS showed the lowest swelling power (4.13 g/g) but highest solubility (86.9%) among native and modified LRS. An increase in light transmittance value suggested a lower retrogradation rate for dual-modified starches, making them more suitable for food application at refrigeration and frozen temperatures. Dual-modified LRS showed the development of fissures and dents on the surface of granules as well as the reduction in peak intensities of OH and CH2 groups in FTIR spectra. Combined modifications (MI and IR) reduced values of pasting parameters and gelatinization properties compared to native and microwaved LRS and showed improved stability to shear thinning during cooking and thermal processing. The sequence of modification also affected the rheological properties; the G′ and G″ of MI-IR LRS were lower (357.41 Pa and 50.16 Pa, respectively) than the IR-MI sample (511.96 Pa and 70.09 Pa, respectively), giving it a soft gel texture. Nevertheless, dual modification of LRS by combining MI and IR made more significant changes in starch characteristics than single modifications.
Starch contributes 70 – 80% of calories in diets and is a key source of glucose and energy for humans; and also finds non‐food applications due to its abundance, renewability, and biodegradability. The conventional starch sources of cassava, potato, wheat, and maize have been widely studied and overexploited; thus, there is increasing interest in the utilization and applications of a great variety of underutilized, non‐conventional, and novel starch sources with singular characteristics, but their technological applications are still at infancy. Non‐conventional starches display comparable properties to conventional starches, and their exploitation is linked to regional availability, the social and cultural significance of the starch sources, by‐product valorization, and technological advantages over conventional starches. They can compete favorably with or complement conventional starches for domestic and industrial applications, but information on these starches is still limited to fundamental knowledge. The unification and standardization of research methods are vital for improving yield, purity, and appropriate data comparison. In‐depth studies are also necessary for a proper understanding of the structure‐function‐utilization relationships of the individual sources, in addition to modification strategies for expanding their range of functionalities and providing the framework for novel and extended applications. This review aims to present a comparative state of the art on the sources, characteristic compositions, properties, and techno‐functional applications of non‐conventional starches. Suggestions on future research interests are also proposed to further improve the understanding and expand the potential utilizations of non‐conventional starches .This article is protected by copyright. All rights reserved
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