Freeze-dried Starch Research Articles

Dual-function starch aerogels: Nutraceutical carriers for iron and folic acid delivery

Iron and folic acid are especially important in pregnancy, where supplementation is often the only path to prevent anemia. Despite the available commercial solutions, the challenges of enhancing nutrient absorption and reducing side effects foster the search for novel approaches. In this work, freeze-dried starch aerogels were developed to act as nutraceutical carriers for co-delivery and tested under simulated digestion conditions. Iron and folic acid were loaded into starch gels, both separately and mixed. Iron presented a faster release than folic acid in intestinal conditions, reaching 75–80 % after 10 and 90 min, respectively. Molecular modeling suggests that folic acid interacts with amylose agglomerates in water by hydrogen bonds, probably delaying its release. Co-delivery of these nutraceuticals seems to not affect the release behavior. The Korsmeyer-Peppas kinetic model fits well to all release profiles. The proposed starch aerogel is a promising solution and further development can increase its competitiveness against conventional supplements.

A novel strategy for improving drying efficiency and quality of cream mushroom soup based on microwave pre-gelatinization and infrared freeze-drying

The present study was carried out to achieve a more efficient dehydration process along with low undesirable quality decrease for cream mushroom soup (CMS) by combining microwave pre-gelatinization (MPG) with infrared freeze-drying (IRFD). Wheat flour was gelatinized using a microwave heating unit for different times, and was used in CMS formulations. Freeze drying (FD) was carried out using conventional as well as IRFD and drying time, energy consumption and product quality characteristics (flavor, viscosity of rehydrate juice; moisture absorption and crystallinity of dried soup solid) of CMS were studied. Compared to FD, IRFD reduced the drying time and energy consumption by 23.81% and 28.43%, respectively. The microwave pre-gelatinization of wheat flour and subsequent use in IRFD, while in comparing with single infrared freeze drying, did not affect drying time and energy consumption; however, it significantly improved the flavor and viscosity of soup upon rehydration, and reduced the tendency to retrogradation. The microwave pre-gelatinization time of 120 s at 8 W/g energy level was found to be the most suitable condition for microwave pre-gelatinization of wheat flour. Industrial relevanceUndesirable decrease of viscosity in starch containing soup and high energy consumption of traditional freeze-drying limit the large-scale industrial production of freeze-dried starch containing product. Therefore, inhibiting viscosity reduction and reducing production cost are the crucial steps for industrial production of freeze-dried cream mushroom soup. Microwave pre-gelatinization and infrared freeze-drying have made outstanding contributions on improving starch stability and reducing drying energy consumption, respectively, which caters to the preferences of industrial production and can be used in industrial production of freeze-dried instant cream mushroom soup.

Behaviors of starches evaluated at high heating temperatures using a new model of Rapid Visco Analyzer ‒ RVA 4800

Rapid Visco Analyzer (RVA) is a reliable viscometer that is commonly utilized to measure the pasting properties of starch. The conventional model of RVA can only determine starch pasting properties at heating temperatures up to 95 °C, which thus cannot evaluate the performance of starch related to high-temperature processing, such as retorting, jet-cooking and extrusion. In this study, RVA 4800 ‒ the latest model of the viscometer having high-temperature capability ‒ was deployed to determine the pasting properties of representative waxy, normal and high-amylose starches of 1.8–69.7% amylose contents at heating temperatures of 95–140 °C. As the temperature increased from 95 to 140 °C, the pasting temperatures and peak viscosities of most waxy and normal starches remained unchanged, but their holding strengths and final viscosities decreased, which could be attributed to thixotropic breakdown and thermal degradation of starch molecules. Consequently, the paste adhesiveness or gel hardness of most waxy and normal starches was reduced at higher temperatures. By contrast, heating at temperatures above 120 °C completely gelatinized wrinkled pea and high-amylose maize starches, allowing the starch granules to swell for viscosity development and subsequent gel formation. Matrix structures of the freeze-dried starch pastes and gels were observed under scanning electron microscope to elucidate how the changes at granular and molecular levels at the tested cooking temperatures influenced the pasting and gelling properties of different starches. This research offered new insights into the relationships between the thermal properties, pasting properties and gelling ability of various starches at heating temperatures of 95–140 °C by using RVA 4800.

11. フリーズドライの新分野への応用について(第3報) : フリーズドライ澱粉のα化度と膨潤度について(2)(平成4年度第38回凍結及び乾燥研究会研究報告)

11. フリーズドライの新分野への応用について(第3報) : フリーズドライ澱粉のα化度と膨潤度について(2)(平成4年度第38回凍結及び乾燥研究会研究報告)

Drying methods used in starch isolation change properties of C-type chestnut (Castanea mollissima) starches

The effect of different drying methods used in starch isolation on structural and functional properties of Chinese chestnut starches was investigated. Freeze-dried (FD) starch granules exhibited some scratches and pores on their surface, which were not observed for ethanol-dried (ED) and oven-dried (OD) starch granules. ED starch showed the highest relative crystallinity and short-range molecular order of double helices, followed by OD starch, and FD starch showed the lowest values. These results indicated that freeze drying disrupted the ordered structure of starch granules. At 92.5 °C, OD starch exhibited the highest swelling power, whereas FD starch showed the lowest swelling power. ED starch showed higher gelatinization temperatures and enthalpy changes than OD and FD starches, indicating that ED starch contained higher amount of crystallites than did OD and FD starches. FD and OD starches were hydrolyzed more greatly by alpha-amylase and amyloglucosidase compared with ED starch. Our results showed that freeze-drying disrupted the ordered structure of chestnut starch and it is not preferred for starch isolation.

Starch–cassia gum interactions: A microstructure – Rheology study

We present for the first time the interactions of starch and cassia gum – a novel galactomannan recently approved for use in food processing. Viscoelastic, pasting and microstructural characterization of various starches (waxy; high amylose; normal; cross-linked waxy corn starch; potato starch) containing different levels of the cassia gum was carried out. Significant changes were observed in the morphology of granule remnants formed during gelatinization in the starch pastes prepared with and without the addition of cassia gum. The freeze-dried starch–cassia gum pastes presented a shrunken and tight arrangement of the starch granule remnants, when studied by scanning electron microscopy. A significant reduction in the granule remnant size was also calculated using laser diffraction particle size analysis. The extent of interaction with cassia gum differed significantly among the various starch types. All the unmodified corn starches recorded an increase in peak viscosity at all levels of the cassia gum addition. An increase in the final viscosity of these starches was also observed by the addition of cassia gum, with high amylose and normal corn starch showing the maximum. Similarly, the extent of breakdown and setback viscosity also differed among the different starch types. Ranges of dynamic rheological measurements (temperature, time and frequency sweeps) were performed within the viscoelastic zones. Rheological parameters, such as storage modulus ( G′), loss modulus ( G″) and the gelatinization temperature ( T gel), of the corn starches during the heating cycle were observed to increase, when cassia gum was present at lower levels. The starch–gum systems also exhibited higher tan δ values during both the heating and the cooling cycles, indicating the dominance of the viscous modulus. The G′ and G″ of all the corn starch gels containing cassia gum showed higher values throughout the frequency sweep range. However, the increase in G′ and G″ of different starches was not always consistent with the increase in cassia gum levels. The changes in rheological behaviour during storage of the starch gels, aged on the plate of the rheometer and then studied through time sweeps at 5 °C and frequency sweeps at 25 °C, suggested that the starch gels containing cassia gum had less pronounced changes in the rheological parameters than had their control counterparts.

An NMR protocol for determining ice crystal size distributions during freezing and pore size distributions during freeze-drying

Nuclear magnetic resonance water proton relaxometry is widely used to investigate pore size distributions and pore connectivity in brine-saturated porous rocks and construction materials. In this paper we show that, by replacing water with acetone, a similar method can be used to probe the porous structure of freeze-dried starch gels and therefore the ice crystal size distribution in frozen starch gels. The method relies on the observation that the starch surface acts as a powerful relaxation sink for acetone proton transverse magnetization so that Brownstein-Tarr theory can be used to extract the pore size distribution from the relaxation data. In addition the relaxation time distribution is found to depend on the spectrometer frequency and the Carr-Purcell-Meiboom-Gill pulse spacing, consistent with the existence of large susceptibility-induced field gradients within the pores. The potential of this approach for noninvasively measuring ice crystal size distributions during freezing and pore size distributions during freeze-drying in other food systems is discussed.

Microstructural characterization of starch systems by NMR relaxation and q-space microscopy

Nuclear magnetic resonance (NMR) relaxation and q-space diffusion measurements have been used to probe the microscopic water distribution in a variety of starch-based systems, including packed beds of native starch granules with varying water contents, starch gels, and freeze-dried starch gels. The q-space data for the granular beds is compared with a variety of theoretical models and conforms best to unbounded diffusion in a lower dimensional space. In contrast to some earlier reports, the data for the gelatinized samples are not anomalous and conform to simple unrestricted diffusion in a three-dimensional space. The paper concludes with a novel method for probing pore size distribution in freeze-dried starch gels by infusion of acetone.