Free radical formation in UV- and gamma-irradiated cassava starch

doi:10.1016/S0144-8617(00)00268-X

Carbohydrate Polymers

Volume 44, Issue 3, March 2001, Pages 269-271

https://doi.org/10.1016/S0144-8617(00)00268-X Get rights and content

Abstract

Cassava starch is degraded by UV irradiation, particularly when previously acidified with lactic acid. Gamma irradiation also induces starch degradation through the formation of free radicals. The aim of this work was to confirm the hypothesis that free radicals are formed in starch through UV treatment and to compare free radical formation and the extent of degradation in native or acidified starches as a result of UV and gamma irradiation. Both types of irradiation result in a decrease in starch intrinsic viscosity. Electronic spin resonance (ESR) shows that radicals formed in UV irradiated samples are similar to those produced by gamma irradiation.

Introduction

The treatment of starch by UV light, with or without a photosensitizer (Phillips & Rickards, 1969), induces changes in its functional properties: it increases water binding capacity and solubility (Gholap, Marondeze & Tomasik, 1993) and decreases hot paste viscosity (Fiedorowicz, Tomasick & Lim, 1999). The latter phenomenon can also be observed after treatment with natural sunlight, particularly with cassava starch that has been previously acidified with lactic acid (Mestres and Rouau, 1997, Fiedorowicz et al., 1999, Nunes, 1994, Plata-Oviedo and Camargo, 1998).

Sunlight or UV irradiation do not seem to alter the crystalline structure of starch; the gelatinization enthalpy remains mainly unchanged (Mestres and Rouau, 1997, Fiedorowicz et al., 1999). However, irradiation decreases the intrinsic viscosity (Merlin and Fouassier, 1981, Mestres and Rouau, 1997) and could also promote starch cross-linking under oxygen (Fiedorowicz et al., 1999). UV photodegradation of starch results in glycosidic bond cleavages, with a shortening of the amylose chain and a debranching of the amylopectin chain, through free radical formation (Merlin & Fouassier, 1981). Some studies suggest that free radicals produced by UV irradiation are identical to those produced during thermal treatments (Tomasick & Zaranyika, 1995) or to those generated by additives such as sulphite or ascorbic acid (Sriburi, Hill & Barclay, 1999). However, the starch photodegradation mechanism remains unclear.

Electronic spin resonance (ESR) experiments have made a major contribution to our understanding of the mechanism of starch degradation after gamma irradiation. It has been reported that gamma irradiation induces free radicals at the C₁ position on the glucose molecule (Raffi and Agnel, 1983, Raffi et al., 1985). The aim of this work was to confirm the hypothesis that free radicals are formed in starch after UV treatment and to compare free radical formation and the extent of starch degradation after UV and gamma irradiation.

Section snippets

Materials and methods

Cassava starch (Manihot esculenta Crantz) used was a commercial sample from Lorenz Co. (São Paulo, Brazil). Amylopectin was extracted from the starch according the method described by Banks and Greenwood (1967). Dextrin 10 derived from corn starch was obtained from Fluka BioChemika.

The cassava starch, amylopectin and dextrin were acidified with lactic acid (Sigma L1250) solution (2% w/w) for 10 min at room temperature then dried in an oven at 25°C for 24 h, giving a final water content of 12%

ESR

The native cassava starch did not show any ESR signal. The ESR patterns of the cassava starch samples after UV or gamma radiation (Fig. 1) showed different shapes depending on water content and storage time after irradiation. They can present two main signals, AA′ and BB′ (Table 1), according to the notation of the signals already found in gamma-irradiated starches (Raffi & Agnel, 1983), or a main BB′ signal; these two signals are singlets. Merlin and Fouassier (1981) also noted the presence of

Acknowledgements

The authors thank the Brazilian Ministry of Education for its research grant.

References (14)

W Banks et al.
The fractionation of laboratory isolated cereal starch using dimethylsulfoxide
Starch
(1967)
M Fiedorowicz et al.
Molecular distribution and pasting properties of UV irradiated corn starches
Starch
(1999)
A.V Gholap et al.
Dextrinization of starch with nitrogen laser
Starch
(1993)
A Merlin et al.
Etude de radicaux libres formés par irradiation ultraviolette de l'amidon: application aux reactions de photodegradation et de photogreffage
Makromolecular Chemistry; Macromolecular Symposium
(1981)
C Mestres et al.
Influence of natural fermentation and drying conditions on the physicochemical characteristics of cassava starch
Journal of the Science of Food and Agriculture
(1997)
J.P Michel et al.
Experimental study of the depolymerization of starch under the combined action of protons and gamma radiation
Starch
(1980)
Nunes, O. L. G. S. (1994). Efeito da radiaçao ultravioleta sobre as propriedades funcionais da fécula de mandioca...

There are more references available in the full text version of this article.

Cited by (118)

Altered leaching composition of maize starch granules by irradiative depolymerization: The key role of degraded molecular structure
2023, International Journal of Biological Macromolecules
The molecular composition of starch leachates from starch-based foods has been recently recognised as a crucial determinant of food properties. However, there is limited knowledge on the regulation of this composition through irradiative depolymerization of starch. This research investigates the leaching behaviour of maize starch depolymerized by electron beam irradiation, and the relationship between the composition of leached starch and structures of modified starch granules. The analysis using ¹H NMR spectroscopy confirmed a decrease in the degree of branching (from 4.4 % to 2.8 %), while size-exclusion chromatography identified a newly-derived amylopectin fraction of a smaller hydrodynamic radius (approximately 60–80 nm). The structural properties of the starch granules were also analysed, revealing an increased BET-area of granules and reduced total crystallinity after depolymerization. In the leachates of swollen granules, the bimodal distribution of starch molecules evolves into unimodal with the increase of the irradiative dosage, while modified starch leached more starch molecules with R_h < 10 nm. The results of principal component analysis and Pearson correlation analysis indicate that the degree of branching of degraded starch molecules, as well as the newly-derived amylopectin fraction, significantly correlates (p < 0.01) with the molecular size of leached starch molecules (R_h < 10 nm). It is thus proposed that the cleavage of α-1,6 linkage may be a critical factor in controlling the leaching process of irradiated starch granules. This study highlights the potential of irradiative degradation to control the molecular composition and structure of starch leachates, thereby optimizing the properties of starch-based foods.
Effects of electron beam irradiation pretreatment on the substitution degree, multiscale structure and physicochemical properties of OSA-esterified rice starch
2023, Food Bioscience
In order to investigate the effect of electron beam irradiation (EBI) pretreatment on the structure and physicochemical properties of octenyl succinic acid (OSA) esterified rice starch. In this study, rice starch was pretreated with EBI (2, 4, 6 KGy) followed by OSA esterification (3%, 6%). EBI pretreatment significantly increased the OSA-esterified starch's degree of substitution (0.0173–0.0305). However, the relative crystallinity of OSA-esterified starch decreased after EBI pretreatment. And the peak viscosity, trough viscosity and final viscosity of starch decreased significantly with the increase in irradiation dose. Moreover, EBI pretreatment significantly reduced gelatinization temperature and B₃ chain content of OSA-esterified starch, and significantly increased transparency, solubility, swelling power and A chain content. In addition, OSA-esterified starch's RDS content decreased and RS + SDS content increased after EBI pretreatment. The PCA results suggest that EBI may affect the physicochemical properties of starch by acting on its structure. The results showed that EBI pretreatment improved the physicochemical and functional properties of OSA-esterified starch, which is expected to broaden its application scope.
Characterization of UVA-irradiated wheat paste and paste-coated paper
2023, Journal of Cultural Heritage
Starch paste has been the main adhesive of choice for paper conservation until now. Studies evaluating the properties of paste-coated paper under UVA irradiation conditions are limited but necessary to enable conservators for a proper choice of materials in terms of durability. In this paper, SEM, FTIR, Raman, and measurements of mechanical properties were used to investigate the aging features of UVA-irradiated paste-coated paper. The increased macro and micro physical and chemical changes with increasing UVA exposure time indicated the degradation of paste and paper polymers. The pH and spectroscopic analyses indicated that the carboxyl groups, which led to the acidity of the sample, were slowly produced with increasing irradiation, and the pH of the paste was lower than that of the paper samples when exposed for the same amount of time. The change in crystallinity also affected the degradation rate of paste-coated papers. SEM observations showed that the paste was destroyed more easily than the paper fibers, a higher concentration of paste caused the paper fibers to break, and a lower concentration of paste damaged both the paste and paper fibers. The present study suggests that an appropriate concentration of paste coated on the paper surface could improve the irradiation stability of paper samples for paste-restored paper artifacts.
The effect of non-thermal physical modification on the structure, properties and chemical activity of starch: A review
2023, International Journal of Biological Macromolecules
Non-thermal physical treatments has obvious advantages in regulating the structure and properties of starch compared with chemical treatment. Hance, this article summarized and compared the effects of three kinds of non-thermal physical treatments including grinding and ball milling, high hydrostatic pressure and ultrasonic on the structure, properties and chemical activity of starches from different plants. The potential applications of non-thermal physical modified starch were introduced. And strategies to solve the problems in the current research were put forward. It is found that although starch has a dense structure, the starch granules could be deformed under three kinds of non-thermal physical treatments, which could damage the granule morphology, microstructure, and crystal structure of starch, reduce particle size, increase solubility and swelling power, and promote starch gelatinization. Three kinds of non-thermal physical treated starch could be used as flocculant thickener, starch based edible films and fat substitutes. Non-thermal physical treatments caused the structure of starch to undergo three stages, which were similar to mechanochemical effects. When starch was in the stress stage and the transition stage from aggregation to agglomeration, its active sites significantly increase and move inward, ultimately leading to a significant increase in the chemical activity of starch.
Physical modification of high amylose starch using electron beam irradiation and heat moisture treatment: The effect on multi-scale structure and in vitro digestibility
2023, Food Chemistry
This study explores a new strategy for manipulating the digestibility of high-amylose maize starch (HAMS) through combinative modifications, namely depolymerization via electron beam irradiation (EBI) followed by reorganizing glucan chains via heat moisture treatment (HMT). The results show that semi-crystalline structure, morphological features and thermal properties of HAMS remained similar. However, EBI increased branching degree of the starch at high irradiation dosage (20 kGy), resulting in more readily leached amylose during heating. HMT increased the relative crystallinity (3.9–5.4% increase) and V-type fraction (0.6–1.9% increase), without significant changes (p > 0.05) in gelatinization onset temperature, peak temperature and enthalpy. Under simulated gastrointestinal conditions, the combination of EBI and HMT either had no effect or negative effect on starch enzymatic resistance, depending on the irradiation dosage. These results suggest that the depolymerization by EBI predominantly affects the changes in enzyme resistance, rather than the growth and perfection of crystallites induced by HMT.
Ball-milling: A sustainable and green approach for starch modification
2023, International Journal of Biological Macromolecules
Ball-milling is a low-cost and green technology that offers mechanical actions (shear, friction, collision, and impact) to modify and reduce starch to nanoscale size. It is one of the physical modification techniques used to reduce the relative crystallinity and improve the digestibility of starch to their better utility. Ball-milling alters surface morphology, improving the overall surface area and texture of starch granules. This approach also can improve functional properties, including swelling, solubility, and water solubility, with increased energy supplied. Further, the increased surface area of starch particles and subsequent increase in active sites enhance chemical reactions and alteration in structural transformations and physical and chemical properties. This review is about current information on the impact of ball-milling on the compositions, fine structures, morphological, thermal, and rheological characteristics of starch granules. Furthermore, ball-milling is an efficient approach for the development of high-quality starches for applications in the food and non-food industries. There is also an attempt to compare ball-milled starches from various botanical sources.

View all citing articles on Scopus

View full text

Short CommunicationFree radical formation in UV- and gamma-irradiated cassava starch

Abstract

Introduction

Section snippets

Materials and methods

ESR

Acknowledgements

The fractionation of laboratory isolated cereal starch using dimethylsulfoxide

Starch

Molecular distribution and pasting properties of UV irradiated corn starches

Starch

Dextrinization of starch with nitrogen laser

Starch

Etude de radicaux libres formés par irradiation ultraviolette de l'amidon: application aux reactions de photodegradation et de photogreffage

Makromolecular Chemistry; Macromolecular Symposium

Influence of natural fermentation and drying conditions on the physicochemical characteristics of cassava starch

Journal of the Science of Food and Agriculture

Experimental study of the depolymerization of starch under the combined action of protons and gamma radiation

Starch

Short Communication
Free radical formation in UV- and gamma-irradiated cassava starch