R. Hoover

Composition, molecular structure, and physicochemical properties of tuber and root starches : a review

Abstract The major carbohydrate of tuber and root crops is starch, which accounts for 16–24% of their total weight. In recent years, substantial progress has been made in understanding the relationship between starch structure and physicochemical properties. However, these studies have been mainly on cereal starches. The present status of knowledge on the composition, structure, gelatinization retrogradation, digestibility and rheological properties of tuber and root starches is reviewed. In addition, present concepts of granule structure, gelatinization, retrogradation and rheology are also reviewed. Future research needs in the area of tuber and root starches are discussed.

Effect of heat-moisture treatment on the structure and physicochemical properties of cereal, legume, and tuber starches

Native wheat, oat, lentil, yam, and potato starches were heat treated at 100 degrees C for 16 h at moisture contents between 10 and 30%. The heat treatment did not change granule size and shape. In oat starch, granules were less compactly packed after heat treatment. The X-ray diffraction intensities increased in wheat, oat, and lentil starches, but decreased in potato and yam. The X-ray patterns of wheat and oat starches remained unchanged, while those of lentil, potato, and yam starches became more cereal-like. In all starches, the swelling factor and amylose leaching decreased, being more pronounced in potato. Heat treatment induced complex formation between amylose and native lipids. Differential scanning calorimetry of the heat-treated samples showed a broadening of the gelatinization-temperature range and a shifting of the endothermal transition towards higher temperatures. These changes were more pronounced in potato starch. The gelatinization enthalpy of wheat, oat, and lentil starches remained unchanged, but those of potato and yam starches decreased on heat treatment. Heat treatment increased the 95 degrees C viscosity of wheat starch, but decreased those of oat lentil, potato, and yam starches. In all starches, thermal and shear stability increased after heat treatment. Acid hydrolysis decreased on heat treatment of wheat and lentil starches, but increased in oat, potato, and yam starches. However, in potato and yam starches, the foregoing trend was evident only during the first seven days of hydrolysis. Thereafter, acid hydrolysis was more pronounced in native than in heat-treated starches. The susceptibility towards hydrolysis by porcine pancreatic alpha amylase decreased on heat treatment of wheat and lentil starches, whereas increases were observed for oat, potato, and yam starches. The results indicated that the extent of starch-chain associations within the amorphous regions and the degree of crystalline order are altered during heat-moisture treatment. The magnitude of these changes were found to be dependent upon the moisture content during heat treatment and on the starch source.

Pea Starch: Composition, Structure and Properties — A Review

Recently, pea has developed into a major protein crop in Western Canada. In the search for new food protein resources, small commercial facilities in Canada have engaged in manufacturing protein concentrates from pea by air classification or wet milling techniques. However, the major products from these processes are either crude or refined pea starches. Pea starch has been utilized almost exclusively for industrial application. A major factor, which has an adverse effect on the widespread utilization of pea starch in food industry, it its high extent of retrogradation. This review summarizes the present knowledge on composition, structure and physiochemical properties of smooth and wrinkled seeded pea starches with a view to providing suggestions for needed research to improve the utilization of pea starches in the food industry.

Composition, molecular structure, and physicochemical properties of starches from four field pea (Pisum sativum L.) cultivars

Abstract Starch from four cultivars (Carneval, Carrera, Grande and Keoma) of field pea ( Pisum sativum L.) was isolated and its physicochemical properties were compared with those of other legume starches. The yield of starch was in the range 32.7–33.5% on a whole seed basis. The starch granules were round to elliptical with smooth surfaces. The free lipid was 0.05% in all starches. However, bound and total lipids ranged from 0.24 to 0.29% and from 0.28 to 0.34%, respectively. The total amylose content ranged from 48.8–49.6%, of which 10.9–12.3% was complexed by native lipid. The degree of polymerization (DP) of amyloses ranged from 1300 to 1350. The chain length distributions of debranched amylopectins of the starches were analyzed using high performance anion-exchange chromatography equipped with a post-column amyloglucosidase reactor and a pulsed amperometric detector. The proportion of short branch chains, of chain length DP 6-12, ranged from 16.2 to 18.6%. Keoma displayed a larger portion (19.4%) of long branch chains (DP>37) than the other three starches (16.2–16.9%). The average amylopectin branch chain length ranged from 22.9 to 24.2. The maximum detectable DP was higher in Keoma (71) than in the other three starches (64–65). The X-ray pattern was of the ‘C’ type. The relative crystallinity was in the range 20.8–25.1%. The proportion of ‘B’ polymorphic form was higher in Keoma (25.6%) than in the other three starches (22.1–24.1%). There were no significant differences in swelling factor. The extent of amylose leaching at 95°C ranged from 25.20 to 26.85. All four starches exhibited nearly identical gelatinization transition temperatures and enthalpies. However, the gelatinization temperature range ( T c – T o ) followed the order: Grande∼Keoma>Carneval∼Carrera. The four starches showed identical pasting temperatures and exhibited only marginal differences with respect to 95°C viscosity and to the increase in consistency during the holding period at 95°C. However, the set-back viscosity for Carneval was lower than that of the other starches. There were no significant differences in the extent of acid hydrolysis. However, susceptibility towards hydrolysis by α-amylase followed the order: Carneval∼Carrera∼Grande>Keoma. The extent of retrogradation (monitored by changes in enthalpy) during storage at 40°C/24 h followed the order: Carneval>Carrera>Grande>Keoma. However, differences in the extent of retrogradation among starches were not discernable by freeze-thaw stability measurements.

In vitro and in vivo hydrolysis of legume starches by α-amylase and resistant starch formation in legumes—a review

Abstract Starch represents the major source of available carbohydrate in the human diet. Starch is the most abundant (22–45%) carbohydrate in the legume seed. The rate of starch digestion in legumes is lower both in vitro and in vivo, than that of cereals. In vivo, starch is hydrolyzed by salivary and pancreatic α-amylase. However, a proportion of starch in starchy foods generally escapes complete digestion. This fraction is called ‘resistant starch’. Resistance starch has properties similar to fermentable fibers. This review summarizes the current knowledge on: (1) the extent of in vitro hydrolysis of native legume starches by α-amylases of different origin; (2) the structural and morphological changes that occur in legume starches as a result of α-amylolysis; (3) the reactivity of amylases towards gelatinized, retrograded and modified legume starches; (4) effect of food processing on in vitro hydrolysis; (5) in vivo digestibility; and (6) resistant starch formation in legumes.

The Impact of Heat-Moisture Treatment on Molecular Structures and Properties of Starches Isolated from Different Botanical Sources

Heat-moisture treatment is a hydrothermal treatment that changes the physicochemical properties of starches by facilitating starch chain interactions within the amorphous and crystalline domains and/or by disrupting starch crystallites. The extent of these changes is influenced by starch composition, moisture content and temperature during treatment, and by the organization of amylose and amylopectin chains within native starch granules. During heat-moisture treatment starch granules at low moisture levels [(<35% water (w/w)] are heated at a temperature above the glass transition temperature (T g ) but below the gelatinization temperature for a fixed period of time. Significant progress in heat-moisture treatment has been made during the last 15 years, as reflected by numerous publications on this subject. Therefore, this review summarizes the current knowledge on the impact of heat-moisture treatment on the composition, granule morphology, crystallinity, X-ray pattern, granular swelling, amylose leaching, pasting properties, gelatinization and retrogradation parameters, and susceptibility towards α-amylase and acid hydrolysis. The application of heat-moisture treatment in the food industry is also reviewed. Recommendations for future research are outlined.

Physicochemical characterization of mung bean starch

Abstract Starch from mung bean (Vigna radiata) was isolated and some of the important characteristics determined. The yield of starch was 31.1% on a whole-seed basis. The shape of the starch granule was oval to round to bean shaped, with granules 7–26 μ m in diameter. Scanning electron micrographs revealed the presence of smooth surfaces. The gelatinization temperature range was 58–67–82°C and the enthalpy of gelatinization was 18.5 J/g. The total amylose content was 45.3%, of which 12.1% was complexed by native lipids. The X-ray diffraction pattern was of the ‘C’ type and the X-ray intensities were much stronger than in other legume starches. The starch exhibited a high swelling factor ( 43.6 at 95°C) in water. The viscoamylographic examination of the starch paste (6% w/v) showed the absence of a peak viscosity, a low 95°C viscosity [200 Brabender units (BU)], an increase in consistency ( 140 BU) during the holding cycle at 95°C and a set-back of 220 BU. Native granules were readily hydrolyzed by porcine pancreatic α -amylase (76.4% in 72 h). Retrogradation of mung bean starch (as measured by changes in syneresis, gel strength, enthalpy and X-ray diffraction intensities) appeared to be more severe than in other legume starches.

The impact of single and dual hydrothermal modifications on the molecular structure and physicochemical properties of normal corn starch

Effect of single and dual hydrothermal modifications with annealing (ANN) and heat-moisture treatment (HMT) on molecular structure and physicochemical properties of corn starch was investigated. Normal corn starch was modified by ANN at 70% moisture at 50 degrees C for 24h and HMT at 30% moisture at 120 degrees C for 24h as well as by the combination of ANN and HMT. The apparent amylose content and swelling factor (SF) decreased on ANN and HMT, but amylose leaching (AML) increased. These changes were more pronounced on dual modification. The crystallinity (determined by X-ray diffraction), the gelatinization enthalpy (determined by differential scanning calorimetry) and ratio of 1047 cm(-1)/1022 cm(-1) (determined by Fourier transform infrared spectroscopy) slightly increased on ANN and decreased on HMT. The ANN and subsequent HMT (ANN-HMT) resulted in the lowest crystallinity, gelatinization enthalpy and ratio of 1047 cm(-1)/1022 cm(-1). The gelatinization temperature range decreased on ANN but increased on HMT. However, the gelatinization range of dually modified starches (ANN-HMT and HMT-ANN) was between ANN starch and HMT starch. Birefringence remained unchanged on ANN but slightly decreased on HMT as well as dual modification. Average chain length and amount of longer branch chains (DP> or =37) remained almost unchanged on ANN but decreased on HMT and dual modifications (ANN-HMT and HMT-ANN). HMT and dual modifications resulted in highly reduced pasting viscosity. ANN and HMT as well as dual modifications increased RDS content and decreased SDS and RS content.

Effect of heat-moisture treatment on the structure and physicochemical properties of legume starches

Native Green Arrow pea, Eston lentil, Othello pinto bean, black bean and Express field pea starches were heat treated at 100°C for 16h at a moisture content of 30%. The heat treatment did not change granule size or shape. The surfaces of Green Arrow pea and Eston lentil starches were modified after heat treatment. Heat treatment decreased amylose leaching (Green Arrow pea>Express field~Eston Ientil>black bean~pinto bean) and the swelling factor (Eston lentil~Express field pea>Green Arrow pea>black bean~pinto bean). The X-ray diffraction intensities increased in Green Arrow pea starch, but decreased in the other starches (Express field pea>black bean>pinto bean>Eston lentil). However, the X-ray pattern of all starches remained unchanged after heat treatment. Differential scanning calorimetry of the heat treated samples showed broadening of the gelatinization temperature range and a shifting of the endothermal transition towards a higher temperature (Eston lentil~Express field pea>black bean~pinto bean). However, the gelatinization enthalpy (ΔH) of all starches remained unchanged. The susceptibility towards hydrolysis by porcine pancreatic α-amylase increased on heat treatment (black bean>Eston Ientil>Express field pea>pinto bean>Green Arrow pea). The action of α-amylase on the starches decreased ΔH in Eston lentil and Express field pea starches. However, ΔH decreased only marginally in pinto bean and black bean starches. Acid hydrolysis (2.2N HCl) increased on heat treatment (black bean>Express field pea~Eston lentil~pinto bean>Green Arrow pea). The results showed that bonding forces within the amorphous regions of the granule, crystallite orientation and the granule surface (in Green Arrow pea and Eston lentil) are altered during heat treatment. The magnitude of these changes being dependent upon the starch source.

A comparative study of the composition of lipids associated with starch granules from various botanical sources

Lipids from highly purified wheat, rice, corn, fababean, lentil, potato and cassava starches were extracted by acid hydrolysis and by selective solvent extraction with chloroform-methanol 2:1 v/v [CM] at ambient temperature, followed by n-propanol-water 3:1 v/v [PW] at 90–100°C. The acid hydrolyzed extracts which represented the total starch lipid [TSL] content ranged from 0.1% (potato) to 0·8% (corn). The combined action of CM and PW resulted in almost complete removal of starch lipids (>98·6%) from most of the starches, the exception being wheat, where the solvent extraction efficiency (% TSL) was 96·3%. The free lipids in the CM extracts (% TSL) ranged from 5·0% (corn) to 62% (fababean), whereas the free and bound lipids in the PW extracts ranged (% TSL) from 44·2% (potato) to 94·8% (corn). Neutral lipids (NL) formed the major lipid class in the CM extracts of all starches, while in PW extracts these were NL in corn and cassava, NL and phospholipids (PL) in potato, and PL in wheat, rice and fababean. There was a great variation among the starches with respect to the major components of the lipid classes in both CM and PW extracts. Monoacyl lipids were most abundant in cereal starches (>78% TSL). The fatty acid composition of NL, GL and PL in CM and PW extracts was determined.