Interaction of Sucrose with Starch During Dehydration as Shown by Water Sorption

Component interactions in the sucrose-starch-water system were investigated. Starch, sucrose, a mechanical starch:sucrose mixture and four powders obtained by freeze drying dilute aqueous mixtures were equilibrated to a_w ranging from 0.33–0.93. Both raw and gelatinized starch were included. Sucrose-starch interaction was determined by measuring the reduction in water sorption as compared to theoretical. Only the freeze-dried mixtures showed interaction. Interacted sucrose, calculated as the sucrose that did not bind water, (1) decreased from a maximum at 0.86 a_w to zero at 0.936 a_w, and (2) rose sharply with increasing sucrose-starch ratio to a maximum at a ratio of 0.4 and decreased to zero with further increase in ratio to 1.5. More sucrose interacted with gelatinized than raw starch.     

Interaction of Sodium Chloride With Raw Starch in Freeze-Dried Mixtures as Shown by Water Sorption

Mixtures of NaCl and starch, obtained by freeze dehydration of dilute aqueous suspensions of various NaCl:starch ratios, were equilibrated over saturated salt solutions of a, range 0.33 - 0.97. They showed a decreased water sorption at aw above 0.75 as compared to the expected values obtained from the Lang-Steinberg mass balance equation. This suppression was taken to mean that some NaCl interacted with starch. The maximum amount of interacted NaCl was 0.15g per g starch, obtained at 0.75 a,. Interacted NaCl decreased to half maximum as a, increased to 0.93 and drastically decreased to one-tenth maximum when a, reached 0.97. With increasing NaCl content, the interaction rose sharply to a peak at about 0.13 NaCl:starch ratio and decreased to zero at the ratio of about 0.33.     

Starch Cooking with Limited Water as Affected by Zein and Guar Gum

DSC (Differential Scanning Calorimetry) peak temperature of starch was decreased by adding zein, but was increased by adding guar gum. Adding zein increased the initial rate of starch cooking, but adding guar gum decreased it. Kinetic studies were carried out at 115, 125, and 135°C. At25°C, zein absorbed less water than waxy corn starch, especially at water activities >0.6 where guar gum absorbed more water than starch. The strong binding of water by guar gum increased DSC-peak-temperature and decreased the initial rate of starch cooking. The relatively weak binding of water by zein decreased DSC peak temperature and increased the initial rate of starch cooking. Although water sorption data at cooking temperatures are difficult to measure, the kinetic data at these temperatures and DSC data could be used to supplement the sorption data.     

Interaction Between Sodium Chloride and Paracasein as Determined by Water Sorption

The model system, salt-paracasein-water, for binding interactions that influence ripening of salted cheeses was investigated. The amount of salt interacting with protein was calculated from water sorption data in the range 0.76-0.95 a_w for the system and for pure salt and protein. Calculations showed that the components did not behave independently in that the system behaved less like salt and more like paracasein than expected, evidencing interaction between salt and protein. The amount of interacting salt increased with added salt, decreasing a_w, moisture content during preparation and drying the system. At 0.85 a_w the amount of interacted salt was 0.08 g/g protein when the salt added was 0.30; the maximum interacted salt was about 0.11.     

Starch Conversion During Extrusion as Affected by Added Gelatin

Waxy maize starch was modified by twin-screw extrusion cooking in the presence and absence of gelatin. X-ray diffraction, microscopy, rheology, and differential scanning calorimetry studies showed that, at constant specific mechanical energy and extruder heater temperatures, the degree of starch conversion decreased with increasing levels of gelatin. It was hypothesized that during extrusion cooking, the gelatin acts as a lubricant, protecting the starch from being converted since more mechanical energy would be dissipated in the gelatin phase than the starch phase.     

Starch Digestibility as Affected by Polyphenols and Phytic Acid

The rate of wheat starch digestibility in the presence or absence of polyphenols (catechin or tannic acid) and/or phytic acid at concentrations found in legumes was determined in an in vitro dialysis system. Addition of tannic acid and phytic acid reduced the starch digestibility 13 and 60% respectively, at 5 hr. Combined tannic and phytic acid reduced the digestibility at a level (63%) which did not differ significantly from that with only phytic acid. Catechin had no significant effect on rate of starch digestibility.     

Interaction of Solutes with Raw Starch during Desorption as shown by Water Retention

The objective was to study interaction of salt and sucrose with raw starch as determined from water retention at a given a_w. NaCI-starch mixtures were 5:95, 10:90, 15:85, and 25:75. Sucrose-starch mixtures were 1:9, 2:8, 1:1, and 9:1. Equilibration was against salt slushes over the water activity range 0.33 to 0.97. At each a_w, as the solute concentration increased above zero, the amount of interacted solute rose to a maximum and then, in contrast to previous findings with protein, declined to zero. For each solute, saturation a_w showed the highest amount of interaction at any solute concentration; the interaction decreased with increasing a_w. At maximum, 87.2% of total NaCl and 56.3% of the total sucrose interacted with starch. These desorption data showed less interaction than previously found for absorption.     

Yield and Functional Properties of Taro Starch as Affected by Ultrasound

Effect of ultrasound pretreatment on yield and functional properties of taro starch was investigated. A three-factor two-level factorial design was employed with treatment time (5 and 10 min), treatment cycle (0.5 and 1), and amplitude of ultrasound (50 and 100 %). Starch yield from ultrasonic treatment varied from 17.45 to 18.97 % compared to 15.29 % in conventional method. The highest yield of 18.97 % was obtained with treatment time 10 min, treatment cycle 0.5, and amplitude 50 %. A significant increase in swelling, solubility, pasting, and texture properties of the ultrasonically extracted starch was observed. A slight decrease in clarity of the starch pastes was also observed after ultrasonic pretreatment, but the differences were not much significant. Freeze-thaw stability of the ultrasonically extracted starches was found to be better compared to starch extracted using conventional method, making them suitable for foods subjected to refrigeration. The whiteness of the ultrasonically extracted starch powders was lower compared to conventionally extracted starch, but the differences were not statistically significant.     

Interaction of Sucrose with Gelatin, Egg Albumin and Gluten in Freeze-Dried Mixtures as Shown by Water Sorption

The objective was to study sucrose-protein interactions in freeze-dried mixtures as shown by water binding data. Gelatin, egg albumin and gluten were included. Sucrose content was varied. Each sample was mixed with water and dried. The powder was equilibrated against known water activity (a_w) ranging from 0.58 to 0.93. The experimental water sorption data at a given a_w was then compared to calculated values obtained from the Lang-Steinberg mass balance equation. Contrary to other systems, samples sorbed more rather than less water than calculated. This was ascribed to sucrose-protein interaction which increased water binding by protein. Amount of interaction at a given a_w was found to be linearly related to the sucrose content. A critical sucrose content was needed to trigger the interaction.     

Compression Properties of Fish-Meat Gel as Affected by Gelatinization of Added Starch

The influence of starch addition on the elastic properties of fish-meat gel was studied by measuring dynamic viscoelasticity, microscopic observation, and compression tests. Samples with pregelatinized starch, and with and without raw starch were studied. The temperature dependence varied according to the size of the starch granules. Starch granule-size/temperature dependence in the free swellable state was higher than in the fish-meat sol (surimi) protein in the heating process. Results indicated that raw starch affected the surimi protein network with a possible “packing effect” of starch granules, which increased the elastic modulus of the fish-meat gel.     

Determination of Sweet Potato Starch Mixed in Kudzu Starch by Moisture Sorption Method

Moisture sorption isotherms of kudzu starch, sweet potato starch, and their mixtures were measured at 20°C by a gravimetric method with a vacuum apparatus. Correlation was found between the mixture ratio of sweet potato starch to kudzu starch and moisture content of the mixed starches at a water activity of 0.750; the correlation coefficient was 0.9955. The moisture sorption method could be used to determine the amount of sweet potato starch mixed in commercial kudzu starch.     

Temperature Dependency of Compression Properties of Fish-meat Gel as Affected by Added Starch

The influence of starch addition on the elastic properties of fish-meat gel was studied by measuring compression and stress relaxation properties and dynamic viscoelasticity. Samples with pregelatinized starch, with and without raw starch, and processed starch were used. Fish-meat gels with starch showed a higher modulus value at 80°C than at 90°C. The gelatinization of starch appeared to be prevented by surimi protein in the fish-meat gel, and so the sample that gelled at 90°C had a lower “packing effect” than the sample that gelled at 80°C. The optimum heating temperature indicated a higher “packing effect” on the surimi protein.     

Effect of Glycerol on Water Vapor Sorption and Mechanical Properties of Starch/Clay Composite Films

Plasticized starch/clay composite films were prepared by casting aqueous solutions containing oxidized corn starch, different concentrations of glycerol as a plasticizer and 5% clay (sodium montmorillonite, Na⁺‐MMT) on the basis of dry starch. The water‐binding properties of the composite films were evaluated by water vapor sorption isotherms at room temperature and various relative humidities (RHs). Mechanical properties and abrasion resistance were also analyzed for the films with varying glycerol contents at 68% RH and room temperature. Changes in water sorption isotherms suggested that glycerol interacted with both water and starch in a complicated way. A saturation phenomenon of glycerol, depending on RH, was observed based on the isotherms. Above this saturation content, phase separation of the system occurred with the appearance of free glycerol. According to mechanical performance and abrasion resistance, as well as water vapor sorption of the starch blend films, the three‐stage transition was presented to be related to the state of glycerol in the blend system, i.e. adsorption of glycerol onto H‐bonding sites of starch, supersaturation of glycerol as plasticizer and further supersaturation of glycerol. Only above the supersaturation content can glycerol play a plasticizer role in starch‐based composites.     

Sorption Behavior of Crawfish Chitosan Films as Affected by Chitosan Extraction Processes and Solvent Types

Effects of chitosan extraction processes and solvent types on sorption behavior of unplasticized crawfish chitosan films were investigated. Four different chitosans prepared from crawfish shell were dissolved in 1% v/v acetic, formic, lactic, or malic acids at 1% w/v concentration. Chitosans dissolved in acetic or formic acid formed flexible and transparent films that are desirable for packaging applications. Chitosan acetate films maintained lower moisture contents at any relative humidity level compared with chitosan formate films. The type of chitosan significantly influenced the sorption isotherms of chitosan formate films but not chitosan acetate films. The Guggenheim‐Anderson‐de Boer, Oswin, and Caurie models (R²= 0.98, 0.95, and 0.95, respectively) could be used to predict sorption behavior of crawfish chitosan acetate and formate films.     

Arsenic Bioaccessibility in Cooked Rice as Affected by Arsenic in Cooking Water

Abstract: Rice can easily accumulate arsenic (As) into its grain and is known to be the highest As‐containing cereal. In addition, the As burden in rice may increase during its processing (such as when cooking using As‐polluted water). The health risk posed by the presence of As in cooked rice depends on its release from the matrix along the digestive system (bioaccessibility). Two types of white polished long‐grain rice, namely, nonparboiled and parboiled (total As: 202 and 190 μg As kg^?1, respectively), were cooked in excess of water with different levels of As (0, 10, 47, 222, and 450 μg As L^?1). The bioaccessibility of As from these cooked rice batches was evaluated with an in vitro dynamic digestion process. Rice cooked with water containing 0 and 10 μg As L^?1 showed lower As concentrations than the raw (uncooked) rice. However, cooking water with relatively high As content (≥47 μg As L^?1) significantly increased the As concentration in the cooked rice up to 8‐ and 9‐fold for the nonparboiled and parboiled rice, respectively. Parboiled rice, which is most widely consumed in South Asia, showed a higher percentage of As bioaccessibility (59% to 99%) than nonparboiled rice (36% to 69%) and most of the As bioaccessible in the cooked rice (80% to 99%) was released easily during the first 2 h of digestion. The estimation of the As intake through cooked rice based on the As bioaccessibility highlights that a few grams of cooked rice (less than 25 g dry weight per day) cooked with highly As contaminated water is equivalent to the amount of As from 2 L water containing the maximum permissible limit (10 μg As L^?1). Practical Application: Studies on As bioaccessibility are needed for determining human As intake from rice for use in accurate risk assessments to establish updated legislation regarding maximum level of As in food. High As bioaccessibility from parboiled rice (consumed by the majority of the people in South Asia), and the findings of high As levels in discarded rice gruel (fed to livestock), has implications for human and animal health.     

Flax Fibers Sorption Properties Influenced by Different Pretreatment Processes

Abstract

The sorption behavior of raw and treated flax fibers was investigated. This paper presents the effect of conventional pretreatment processes (alkaline, acid) in comparison to environmentally friendly enzymatic processes on the sorption ability of flax fibers. Weight-loss, moisture sorption, water retention value and contact angle were determined in order to interpret the pretreatment results. In addition, the influence of the process on the fibers' mechanical properties was studied. The ecological parameters of the treatment wastewaters were analyzed.     

Physicochemical Properties of Sweet Potato Flour and Starch as Affected by Blanching and Processing

The effects of blanching on physicochemical properties of flours and starches prepared from two varieties of sweet potatoes (Mun‐Kai and Negro) were studied and compared. The pasting temperature and peak viscosity of starches, respectively, were 74 and 80 °C and 381 and 433 RVU. The pasting temperature (74.0‐94.8 °C) of flours was greater than that of starch, depending on the variety and blanching process. However, the peak viscosity (ca. 103‐120 RVU) of flours was lower than that of the corresponding starches. Partial gelatinization of starch granules was observed as a result of a 1‐min blanching. Composition of starch and flour was found to affect swelling power and solubility. The starch content of starches, flours from unblanched sweet potato and flours from 1‐min blanched sweet potatoes were 97; 66.3 and 74.9; as well as 36.6 and 40.4%, respectively. Amylose content of flours and starches varied from 17.2‐20.8%.     

Moisture Sorption Hysteresis in Kudzu Starch and Sweet Potato Starch

Moisture sorption hysteresis loops of kudzu starch and sweet potato starch were investigated to help understand the nature of the adsorption-desorption process. The second adsorption isotherms were above the first adsorption isotherms for kudzu starch and sweet potato starch preheated to 110°C. This was explained as an increase in the number of hydrophilic sites due to rupturing of hydrogen bonds. The hysteresis loop for kudzu starch was greater than that for sweet potato starch. This was interpreted as a difference in mesopore volume.     

Resistant Starch Derived from Extruded Corn Starch and Guar Gum as Affected by Acid and Surfactants: Structural Characterization

Corn starches with and without guar gum [10% (w/w)] and 2% (w/w) of diacetyl tartaric acid ester of monoglyceride, sodium stearoyl‐2‐lactylate or citric acid, respectively, were extrusion‐cooked in a twin‐screw extruder at 18% moisture, 150 °C and 180 rpm screw speed. The content of resistant starch was determined by sequential enzymatic digestion. The formation of resistant starch in extruded corn starch was strongly affected by the addition of gum and the different food additives. X‐ray diffraction of the extruded starches gave a V diffraction pattern indicating the effect of extrusion cooking and amylose‐lipid complexes. Enzymatic digestion did not affect the V‐structure, which could apparently be attributed to extrusion cooking. Similarly, differential scanning calorimetric thermograms indicated that all isolated resistant starches exhibited endothermic transitions between 71—178 °C signifying a complex formation between amylose and the emulsifiers and possibly the melting of amylose crystallites in the resistant starch. Purification of the isolated resistant starches by size exclusion‐high performance liquid chromatography showed a dependence of molecular weight on the added additives. Results of differential scanning calorimetry and X‐ray diffraction suggest that amylose‐lipid complexes could also be involved in the formation of resistant starch in extruded cornstarch.     

Bacteriological Quality of Freshly Processed Broiler Chickens as Affected by Carcass Pretreatment and Gamma Irradiation

Chicken carcasses dipped in whey fermented by Streptococcus thermophilus, lactic acid solution or water and irradiated at 2.5 kGy by ⁶⁰Co were evaluated for bacteriological quality on day-1, day-3 and at 3-day intervals for an 18-day storage (4°C) period. Unirradiated carcasses treated similarly were used as control. Gram negative bacteria, Yersinia and Campylobacter counts were significantly (p<0.01) lower in irradiated samples, but no significant (p>0.05) differences were observed among the dipping solutions. Salmonellae were completely eliminated in irradiated samples. Whey fermented by 5. thermophilus reduced the proportion of Salmonella contaminated carcasses from 67% to 20%. As evidenced by the bacterial counts the shelf-life was found to be 15 days for irradiated carcasses compared to about 6 days for the unirradiated samples.