STUDY OF SAGO STARCH (METROXYLON SAGU) GELATINIZATION BY DIFFERENTIAL SCANNING CALORIMETRY

Differential scanning calorimetry (DSC), at various heating rates (1–30C/min) and water:starch ratios (0.1:1–4:1), was used to study gelatinization phenomena of sago starch. The results showed that the gelatinization temperature and enthalpy (Δ H) of starches in excess water were 60–77C and 15.5–15.8 J/g, respectively. Δ H of gelatinization remained substantially the same at excess water contents, but decreased significantly beyond a water:starch ratio of 1.3:1. A single endothermic transition (G) that transformed into a double endotherm (G and M₁) and only M₁ occurred, respectively, at excess, intermediate and limited water contents. At 50% water content, evidence of the M₁ endotherm was observed, and 85C represented the effective conclusion temperature (T_m) at the end of melting for sago starch. The experimental data were treated thermody-namically by applying an equation describing phase transitions of semi-crystalline polymers. The calculated value for the melting point of the undiluted polymer (T_m) was 432 K (R²= 0.96).     

Rheological behaviour of sago (Metroxylon sagu) starch paste

Rheological behaviour of gelatinized sago starch solution was studied over the shear rate range of 13.61–704 s⁻¹ at various concentration and temperature ranges. A power law equation was used to describe the rheological behaviour of the starch solution, while the effect of temperature was evaluated by the Arrhenius equation. The effect of starch concentration on apparent viscosity was studied using the exponential model describing the relationship between apparent viscosity and concentration. Consistency index (κ) increased with concentration and decreased with the increase of temperature. Flow behaviour indices (η) were within the range of 0.495–0.559 which indicated the pseudoplastic nature of gelatinized sago starch. The amount of starch and shear rate affect activation energy (ΔE). Depending on the shear rate and concentration, activation energy varied from 0.619 to 1.756 kcal mol⁻¹. A mathematical relationship correlating the various parameters (temperature, concentrations, shear rates) was tested for its significance and validity.     

Physicochemical Properties of Carboxy-methylated Sago (Metroxylon sagu) Starch

ABSTRACT: Carboxymethyl starch (CMS) with degree of substitution (DS) ranging from 0.1 to 0.32 was prepared from sago ( Metroxylon sagu ) starch in non-aqueous medium using isopropanol as a solvent. The physico-chemical, rheological, and thermal properties of the starches were investigated. At room temperature (25 °C), CMS hydrated readily, resulting in higher swelling power compared with native (unmodified) starch. Light microscopy revealed that CMS granules imbibed more water than native starch at room temperature and thus caused a larger increase in granule size. Some of the CMS granules lost their integrity. Scanning electron microscopic observation revealed fine fissures on the surface of CMS (DS 0.32) granules compared with a relatively smooth surface of native starch granules. Carboxymethylated sago starch exhibited excellent dispersibility and cold water solubility as judged by the absence of peak viscosity in the pasting profile (determined by Rapid ViscoAnalyzer). Pasting profile of CMS was qualitatively similar to pregelatinized starch. Despite exhibiting greater swelling power, CMS showed significantly lower pasting viscosity compared with the native starch. Intrinsic viscosity was also greatly reduced by carboxymethylation. Studies using differential scanning calorimetry (DSC) showed that transition temperatures and enthalpies decreased with an increase of degree of substitution. CMS at higher substitution levels (DS 0.27 and 0.32) showed significantly lower retrogradation tendency, as indicated by lower setback, absence of DSC endotherm upon storage at 4 °C and lower syneresis upon repeated freeze-thaw cycles. The results suggested that retrogradation might be effectively retarded by the presence of the bulky carboxymethyl group.     

Enzymic Extraction of Native Starch from Sago (Metroxylon sagu) Waste Residue

Residual native starch was extracted from sago pith residue using two types of commercial cell‐wall degrading enzymes, Pectinex Ultra SP‐L and Ultrazyme 100G. The first increased starch yield with a shorter incubation period than the second. The superior effect of Pectinex Ultra SP‐L was observed already at 0.5 h, where a wide granule size distribution (8—87 μm) was obtained. A slight increase in the release of granules ranging from 30—60 μm was noted within a 2 h incubation period. However, upon further incubation, the distribution pattern was similar to that of untreated samples. Samples treated with Ultrazyme 100G exhibited a unimodal distribution pattern, with larger granules, ranging from 40—70 μm, being released upon further incubation within a 2 h incubation period. However, all samples exhibited a bimodal distribution upon further incubation.     

Physicochemical Properties of Starch in Sago Palms (Metroxylon sagu) at Different Growth Stages

This study was aimed to examine the physicochemical properties of starch extracted from two different points (base and mid heights) of the sago palms trunks (Metroxylon sagu) of different physiological growth stages namely, ‘Plawei’, ‘Bubul’, ‘Angau Muda’, ‘Angau Tua’ and ‘Late Angau Tua’ stages. The physicochemical properties of sago starch studied were the morphology of starch, amylose content, particle size and distribution profile, pasting, thermal and retrogradation profiles. The results showed significant differences in the amylose and amylopectin content as well as in the granule sizes of starch from the different growth stages. Variation was observed in the proportions of granule sizes and pasting properties of starch from base and mid heights of the different growth stages while slight or insignificant differences was observed in the thermal properties of sago starch.     

Physicochemical,thermal, and rheological properties of acid-hydrolyzed sago (Metroxylon sagu) starch

The effects of acid hydrolysis on physicochemical and rheological properties of sago starch were investigated. Sago starch was hydrolyzed in hydrochloric acid at 50 °C for 6, 12, 18, and 24 h. The molecular weight distribution, physicochemical, thermal, and rheological properties of acid-hydrolyzed sago starch (AHS) were determined. After 24 h of hydrolysis, molecular weight of amylopectin and amylose were decreased to 3.57 × 10⁵ and 6.5 × 10⁴ g/mol, respectively. Differential scanning calorimetry studies showed that the gelatinization temperature and enthalpy of AHS increased with increasing degree of hydrolysis. Hydrolyzed sago starch containing low molecular weight fractions exhibited cold water solubility up to 100%. Setting temperature of AHS decreased with increasing hydrolysis time but amylose content and gel strength increased in the first 12 h of acid hydrolysis but decreased with extended hydrolysis time. Hydrolyzed sago starch in concentrations lower than 8 g starch per 100 g water was cold water soluble and could be used to modify properties of starch for specific applications such as yogurt and concentrated milk processing.     

HIGH-PRESSURE DIFFERENTIAL SCANNING CALORIMETRY (DSC): EQUIPMENT AND TECHNIQUE VALIDATION USING WATER–ICE PHASE-TRANSITION DATA

Understanding phase transition during high‐pressure (HP) processing of foods is important both with respect to optimizing the process and improvement of product quality, but scientific information available in this area is very limited. In this study, the phase‐transition behavior of water was evaluated using a HP differential scanning calorimetry (DSC). Tests were carried out under both isothermal pressure‐scan (P‐scan) and isobaric temperature‐scan (T‐scan) modes with distilled water prefrozen in the sample cell. P‐scan was carried out at 0.3 MPa/min at two temperatures, ?10 and ?20C, and T‐scan was carried out at 0.15C/min at two pressures, 0.1 and 115 MPa. The pressure‐induced phase transition of water was accurately reproduced by the P‐scan test. Ice melting latent heat during P‐scan showed no significant difference (P > 0.05) from the available reference data in literature. The relationship between P‐scan tested (L_m) and reference latent heat was L_m = 0.987 L (R² = 0.99, n = 6) suggesting a mean error less than 2%. T‐scan mode was less appropriate and did not yield promising result. Measured values were less accurate than P‐scan probably because of the influence of large heat capacity of sample cell. However, reliable and reproducible results obtained under P‐scan mode suggested that the HP DSC can be used for the calorimetric determination of pressure‐dependent water‐phase transition in real food systems during HP freezing/thawing operations.     

Effect of Temperature and Starch Concentration on the Intrinsic Viscosity and Critical Concentration of Sago Starch (Metroxylon sagu)

Intrinsic viscosity and critical concentration of sago starch dispersions were studied at different temperatures and presence of solutes (sodium chloride, glucose and sucrose). Ubbelohde capillary viscometer was used to measure relative viscosity. Intrinsic viscosity decreases with an increase in temperature but the critical concentration remained fairly constant over the range of temperature studied. Sodium chloride enhanced the intrinsic viscosity but sugars somehow reduced it. Critical concentration is defined as the point where the starch molecules start to entangle with each other and abruptly enhance viscosity. Sodium chloride enhanced the molecular entanglement and lowered the critical concentration.     

Effect of Pullulanase Debranching of Sago (Metroxylon sagu) Starch at Subgelatinization Temperature on the Yield of Resistant Starch

The effects of pullulanase debranching of sago (Metroxylon sagu) starch in the granular state and subsequent physical treatments on the formation and yield of type III resistant starch (RS 3) have been investigated. Sago starch was enzymatically debranched with pullulanase at 60°C and at pH 5.0 using different enzyme concentrations (24, 30, 40, 50 PUN/g dry starch) which was added to 20% (w/v) starch slurry and incubated for 0 to 48 h. Optimum enzyme concentration of 40 PUN/g dry starch and three debranching times (8, 16 and 24 h) have been selected for subsequent preparation of RS. Granule morphology and molecular weight distribution (MWD) of the debranched and resistant starch were examined. Debranched starch samples showed blurred birefringence patterns, a decrease in amylopectin fraction, an increase in low molecular weight fraction and a broadening of MWD. Debranched starch samples with a maximum RS yield of 7% were obtained at 8 h debranching time. Temperature cycling and incubation at certain temperature and storage time enhanced the formation of RS. Under the conditions used in this study, the optimum conditions to obtain the highest RS yield (11.6%) were 8 h of debranching time, followed by incubation at 80°C for seven days. The MWD analysis showed that RS consisted of material with relatively low degree of polymerization. This study showed that pullulanase treatment of starch in the granular state resulted in limited debranching of amylopectin but the subsequent physical treatments (incubation time/temperature) can be manipulated to promote crystallization and enhance formation of RS 3.     

Development of sago (Metroxylon sagu)-based colorimetric indicator incorporated with butterfly pea (Clitoria ternatea) anthocyanin for intelligent food packaging

Innovation in colorimetric sensors to detect early signs of food spoilage is a growing interest in food safety and quality control. Currently available chemical dyes for sensor applications have concern because of their possible migration into food packaging and food in contact. In this study, a colorimetric indicator was developed using natural butterfly pea (Clitoria ternatea) anthocyanin with Sago (Metroxylon sagu) as polymeric film. The principle was based on pH shift due to chemical processes produced by microorganism causing anthocyanin color to change. The film was fabricated by solvent casting method and characterized by color change at different pH values, total water solubility, swelling rate, and morphological structure. Trials on chicken breast samples in various conditions exhibited that the film indicator responded well according to pH variation enabling a real-time monitoring due to spoilage. Thus, our natural pH indicator with visible color variation allows for simple, economic and safe monitoring of perishable foods.     

胶原蛋白多肽-铬(Ⅲ)螯合物的降血糖机理探讨

观察胶原蛋白多肽-铬（Ⅲ）螯合物的降血糖作用,探讨它降血糖的可能机理.通过腹腔注射四氧嘧啶造小鼠糖尿病模型,观察血糖、肝糖原、葡萄糖激酶等指标.胶原蛋白多肽-铬（Ⅲ）螯合物可以显著地降低血糖,增加肝糖原的合成及葡萄糖激酶的活性.胶原蛋白多肽-铬（Ⅲ）螯合物可降低糖尿病小鼠血糖,促进肝糖原的合成和糖尿病小鼠体内的葡萄糖磷酸化.     

Starch from the Sago (Metroxylon sagu) Palm Tree—Properties,Prospects, and Challenges as a New Industrial Source for Food and Other Uses

ABSTRACT: The common industrial starches are typically derived from cereals (corn, wheat, rice, sorghum), tubers (potato, sweet potato), roots (cassava), and legumes (mung bean, green pea). Sago (Metroxylon sagu Rottb.) starch is perhaps the only example of commercial starch derived from another source, the stem of palm (sago palm). Sago palm has the ability to thrive in the harsh swampy peat environment of certain areas. It is estimated that there are about 2 million ha of natural sago palm forests and about 0.14 million ha of planted sago palm at present, out of a total swamp area of about 20 million ha in Asia and the Pacific Region, most of which are under‐ or nonutilized. Growing in a suitable environment with organized farming practices, sago palm could have a yield potential of up to 25 tons of starch per hectare per year. Sago starch yield per unit area could be about 3 to 4 times higher than that of rice, corn, or wheat, and about 17 times higher than that of cassava. Compared to the common industrial starches, however, sago starch has been somewhat neglected and relatively less attention has been devoted to the sago palm and its starch. Nevertheless, a number of studies have been published covering various aspects of sago starch such as molecular structure, physicochemical and functional properties, chemical/physical modifications, and quality issues. This article is intended to piece together the accumulated knowledge and highlight some pertinent information related to sago palm and sago starch studies.