Starch gelatinization is a process that disrupts the native molecular orders of starch granules and typically occurs during thermal processing in the presence of water.
Protein Quantity at the Air-Solid Interface PublicationKorben Knudson
This research article examines how different lyophilization processes affect the stability of recombinant human growth hormone (rhGH) formulations. Five lyophilization methods that produce glasses with varying specific surface areas and protein distributions are compared. Methods that generate larger ice crystals through annealing or slower freezing, resulting in lower protein levels at the solid-air interface, better retain the secondary structure of rhGH and result in less degradation over storage. The findings suggest that differences in protein degradation between formulations and processes can be largely attributed to the amount of protein present at the solid-air interface after lyophilization, with more surface-located protein being more susceptible to degradation.
This document discusses modified food starches. It begins by explaining that modified starches are normal starches that have been chemically or physically altered. Common modification methods include cross-linking, acid treatment, and oxidation. Modified food starches are used as thickeners, emulsifiers, and stabilizers in foods. They allow foods to have longer shelf lives and help bind ingredients. Some common foods containing modified starches include canned soups, chips, and cheese sauces. The document also discusses retrogradation, which is the process by which starch molecules realign and recrystallize.
Flavonoids are polyphenolic compounds found in plants that act as antioxidants. They have 15 carbon atoms arranged in two benzene rings connected by a 3 carbon chain. There are over 4,000 known flavonoids that are commonly found as flower pigments but also occur in other plant parts. Major classes of flavonoids include flavones, flavonols, flavanones, and isoflavonoids. Flavonoids have important biological functions like repairing damage, protecting plants from toxins and UV radiation, and possess anti-inflammatory, antiviral and antitumor properties in humans.
The document discusses the effect of cross-linking modification on the structural and film-forming characteristics of pearl millet starch. Pearl millet starch was modified using different concentrations of epichlorohydrin (EPI) as a cross-linking agent. The degree of cross-linking increased with higher EPI concentrations. Cross-linked starches showed reduced breakdown and setback viscosity but increased pasting temperature. They also had improved resistance to heat, acid, and shear compared to native starch. The cross-linking improved the moisture barrier properties and mechanical strength of edible films formed from the modified starches.
Protein Quantity at the Air-Solid Interface PublicationKorben Knudson
This research article examines how different lyophilization processes affect the stability of recombinant human growth hormone (rhGH) formulations. Five lyophilization methods that produce glasses with varying specific surface areas and protein distributions are compared. Methods that generate larger ice crystals through annealing or slower freezing, resulting in lower protein levels at the solid-air interface, better retain the secondary structure of rhGH and result in less degradation over storage. The findings suggest that differences in protein degradation between formulations and processes can be largely attributed to the amount of protein present at the solid-air interface after lyophilization, with more surface-located protein being more susceptible to degradation.
This document discusses modified food starches. It begins by explaining that modified starches are normal starches that have been chemically or physically altered. Common modification methods include cross-linking, acid treatment, and oxidation. Modified food starches are used as thickeners, emulsifiers, and stabilizers in foods. They allow foods to have longer shelf lives and help bind ingredients. Some common foods containing modified starches include canned soups, chips, and cheese sauces. The document also discusses retrogradation, which is the process by which starch molecules realign and recrystallize.
Flavonoids are polyphenolic compounds found in plants that act as antioxidants. They have 15 carbon atoms arranged in two benzene rings connected by a 3 carbon chain. There are over 4,000 known flavonoids that are commonly found as flower pigments but also occur in other plant parts. Major classes of flavonoids include flavones, flavonols, flavanones, and isoflavonoids. Flavonoids have important biological functions like repairing damage, protecting plants from toxins and UV radiation, and possess anti-inflammatory, antiviral and antitumor properties in humans.
The document discusses the effect of cross-linking modification on the structural and film-forming characteristics of pearl millet starch. Pearl millet starch was modified using different concentrations of epichlorohydrin (EPI) as a cross-linking agent. The degree of cross-linking increased with higher EPI concentrations. Cross-linked starches showed reduced breakdown and setback viscosity but increased pasting temperature. They also had improved resistance to heat, acid, and shear compared to native starch. The cross-linking improved the moisture barrier properties and mechanical strength of edible films formed from the modified starches.
As per the syllabus prescribed by Rajiv Gandhi University of Health Sciences, Karnataka, for M. Pharm (Pharmaceutical Analysis), 1st semester.
*not all topics have been covered in this file.
Physico-chemical treatments to improve the functional properties and digesti...ShreyaMandal4
The study investigated the effects of heat-moisture treatment (HMT) using an oven and autoclave on the properties of purple yam flour. HMT increased resistant starch and decreased rapidly digestible starch, with autoclaving having a greater impact due to higher heat transfer. Autoclaving transformed the starch crystalline structure from B-type to the more crystalline and resistant A-type, improving the flour's potential as a prebiotic.
Characterizing the freeze–drying behavior of model protein formulationsHau Vu
1) The document examines the freeze-drying behavior of three model proteins (lysozyme, BSA, IgG) under different conditions using various characterization techniques.
2) It finds some differences in freeze-drying behavior between the proteins at higher concentrations where the proteins influence the formulation more, but the differences are minimized at lower concentrations where excipients dominate.
3) Differences in cake morphology were seen between drying conditions and proteins, but protein structure and stability were equivalent for cakes made using different drying conditions.
Biochemical behaviour of different cultivars of potato tuber at different st...vandana hooda
This document summarizes a study on the biochemical behavior of two potato cultivars (K. Chipsona-1 and K. Chipsona-2) stored under different conditions for up to 210 days. The key findings are:
1) Both cultivars stored at 8°C showed higher accumulation of reducing sugars (glucose and fructose) compared to those stored at 12°C, leading to greater browning and poorer chip color at the lower temperature due to the Maillard reaction between sugars and proteins.
2) Sucrose levels initially decreased in both cultivars during the first 150 days of storage and then increased from 150-210 days, with the highest levels at 12
Effect of heat treatment, water activity and storage temperature on the oxida...Omar Zeballos
This document summarizes a study investigating the effects of heat treatment, water activity, storage temperature, and time on the oxidative stability of whole milk powder. Three types of milk powder (low-heat, medium-heat, and high-heat) were stored at two temperatures (25°C and 45°C) and three water activities for up to 63 days. Oxidative stability was assessed using electron spin resonance spectrometry to measure free radicals, TBARS to measure secondary lipid oxidation, fluorescent spectroscopy and size-exclusion HPLC to measure protein damage, and sensory evaluation. Results showed that lipid oxidation increased greatly at 45°C, especially for low-heat powder. Sensory quality declined fastest for low-heat powder stored at
The document summarizes the results of a study on the effect of storage period (0-60 days) on the physicochemical, sensory, and microbiological quality of bakery-flavored ice cream (containing cookies and cakes). Key findings include:
- Total solids, acidity, and specific gravity increased significantly with storage period, while pH, antioxidant activity, and overrun decreased significantly.
- Sensory attributes like appearance, texture, flavor, and overall acceptability significantly decreased with longer storage.
- First dripping time increased and melting rate decreased with storage period.
- Standard plate count and psychrophilic count increased significantly with storage period, indicating microbial deterioration.
This document discusses sperm cryopreservation, including the aims, techniques, factors affecting results, and future issues. The key points are:
- Sperm cryopreservation preserves sperm cells at sub-zero temperatures for future use, such as for fertility treatments. Slow freezing and rapid freezing are two common techniques.
- Factors like cryoprotectants, cooling/thawing rates, and semen quality can impact sperm survival after thawing. Semen preparation before freezing may improve outcomes.
- While some studies found cryopreservation does not affect reproductive success rates with ICSI, its effects on sperm DNA integrity are still unclear and require more research. Proper cryopreservation protocols aim to minimize DNA damage
Sperm cryopreservation is the process of freezing sperm to preserve fertility. It involves adding cryoprotective agents to minimize freezing damage before slowly cooling sperm to -196°C in liquid nitrogen storage. Factors like semen quality, freezing technique, and thawing process can impact sperm survival. While some studies found cryopreservation may damage DNA, properly performed it selectively affects defective sperm and clinical pregnancy rates are similar to fresh sperm. Optimization involves semen preparation, controlled freezing and thawing rates, and cryoprotectant use. Further research is still needed on impacts to DNA and reproductive outcomes.
The document discusses several current projects involving collagen and its applications. It describes developing a collagen-hydroxyapatite scaffold for bone defects, analyzing its pore size and efficacy. It also mentions exploring collagen-silver nanoparticle composites for wound care and using collagen coatings for tissue culture. Developing a hemostatic material using collagen and kaolin for heavy bleeding is also summarized.
This document analyzes the properties of sucrose crystals formed through nucleation of amorphous sucrose solutions. Differential scanning calorimetry was used to investigate how temperature affects the heat capacity of amorphous sucrose solutions and the mass, melting point, and density of recrystallized sucrose crystals. The heat capacities of amorphous sucrose solutions decreased with increasing temperature. The mass of recrystallized crystals varied between trials. Melting points of crystals were about 10°C lower than pure sucrose due to impurities. Densities of crystals were also lower than pure sucrose likely due to residual solution and dissolution during measurement.
This document discusses the effects of stabilizers on ice cream properties. Stabilizers increase mix viscosity and prevent wheying off and phase separation. They aid in suspension and produce a stable foam for packaging. Stabilizers also retard ice and crystal growth during storage fluctuations. They slow moisture migration and prevent shrinkage. Stabilizers provide uniformity and resistance to melting, producing a smooth texture. They decrease phase separation and control overrun. Stabilizers inhibit changes in air cells during storage and decrease melting rate by slowing serum drainage. They increase glass transition temperature and affect thermal conductivity. Hydrocolloid type and content influence flavor release and provide better creaminess and texture.
This presentation discusses cryopreservation of gametes. Cryopreservation is a process that uses very low temperatures, typically with liquid nitrogen at -196°C, to preserve living cells and tissues. Cryoprotective agents are used to protect cells from freezing damage. Techniques discussed include slow freezing, rapid freezing and vitrification. Applications include sperm banking, embryo freezing and ovarian tissue cryopreservation. Both benefits and limitations of cryopreservation are mentioned such as the ability to preserve biological materials long-term but also the risk of cell damage from ice formation or toxic effects of cryoprotectants.
- The quality of frozen foods is influenced by storage temperature, with quality decreasing as temperatures increase. Maintaining temperatures of -18°C is accepted as safe for extended shelf life.
- Temperature fluctuations during storage can cause recrystallization of ice crystals and reduce quality through increased crystal size.
- Factors like freezer burn, moisture migration, lipid oxidation, protein denaturation, and enzymatic browning can negatively impact the quality of frozen foods during storage and must be controlled. Understanding these factors is key to minimizing quality loss.
This document discusses a study on extending the shelf life of peach fruits. Peaches were harvested and dipped in aqueous solutions of 0%, 4%, or 6% calcium chloride for 10 minutes. The fruits were then cold stored at 0-2°C and 85-90% relative humidity for 3 weeks. Various quality parameters of the fruits like firmness, total soluble solids, weight loss, and sensory attributes were measured during cold storage and after storage at room temperature. The results showed that peaches dipped in 6% calcium chloride solution maintained acceptable quality for 3 weeks in cold storage and had a post-storage shelf life of 3 days at room temperature.
This document discusses the use of differential scanning calorimetry (DSC) to analyze various materials including ice melting points, specific heat capacity measurements of materials, starch gelatinization and retrogradation, protein denaturation, oil and fat crystallization, gel formation and melting, glass transition temperatures, and microbial growth measurements. DSC can be used to characterize many phase transitions and thermal properties of foods, polymers, and other materials.
Recent advances of starch based excipients used in extended-releasekarthickravi29
This document reviews recent advances in using modified starches as excipients in extended-release tablets. It discusses various starch derivatives used for this purpose, including retrograded starch, enzymatically modified starch, substituted starches like carboxymethyl starch and starch acetate, cross-linked starch, and grafted starch. Key factors influencing drug release from tablets containing these starches are summarized, such as crystalline structure, specific surface area, degree of substitution, and cross-link degree. The document concludes that physical or chemical modification and enzymatic hydrolysis can be used to control drug release from starch-based tablets by influencing gel formation and digestibility.
1. When milk is concentrated through evaporation, its viscosity increases due to a higher concentration of solids and proteins coagulating.
2. The sterilization process further increases viscosity, with low-temperature-long-time (LTLT) sterilization yielding a thicker product than high-temperature-short-time (HTST).
3. Viscosity decreases over time in storage, especially at higher temperatures, due to age thinning. Some milks may later increase in viscosity or even gel due to interactions between proteins and calcium/magnesium salts.
Potassium sorbate, sodium benzoate and citric acid together with vacuum packing have extended puree shelf life by 3-6 months in our trials at ambient conditions (T<25C).
However, the gap lies on the efficacy of the preservative combination in retarding or stopping the growth of harmful pathogens in the puree, and also their effects on β-carotene retention is unknown.
The document discusses a case study on the crystallization and stability of different crystal forms of the protein lysozyme. Specifically:
- Two crystal modifications of lysozyme (tetragonal and needle-shaped) were obtained and their phase diagrams and stability at different pH levels were analyzed.
- The solubility, crystal structures, and phase transition behavior of the two modifications were examined using various techniques like X-ray powder diffraction and microscopy.
- It was found that tetragonal crystals are more stable in acidic solutions while needle crystals are more stable in basic solutions, and the modifications can transition between each other under certain temperature and pH conditions.
More Related Content
Similar to Influences of temperature cycled storage on retrogradation and in
As per the syllabus prescribed by Rajiv Gandhi University of Health Sciences, Karnataka, for M. Pharm (Pharmaceutical Analysis), 1st semester.
*not all topics have been covered in this file.
Physico-chemical treatments to improve the functional properties and digesti...ShreyaMandal4
The study investigated the effects of heat-moisture treatment (HMT) using an oven and autoclave on the properties of purple yam flour. HMT increased resistant starch and decreased rapidly digestible starch, with autoclaving having a greater impact due to higher heat transfer. Autoclaving transformed the starch crystalline structure from B-type to the more crystalline and resistant A-type, improving the flour's potential as a prebiotic.
Characterizing the freeze–drying behavior of model protein formulationsHau Vu
1) The document examines the freeze-drying behavior of three model proteins (lysozyme, BSA, IgG) under different conditions using various characterization techniques.
2) It finds some differences in freeze-drying behavior between the proteins at higher concentrations where the proteins influence the formulation more, but the differences are minimized at lower concentrations where excipients dominate.
3) Differences in cake morphology were seen between drying conditions and proteins, but protein structure and stability were equivalent for cakes made using different drying conditions.
Biochemical behaviour of different cultivars of potato tuber at different st...vandana hooda
This document summarizes a study on the biochemical behavior of two potato cultivars (K. Chipsona-1 and K. Chipsona-2) stored under different conditions for up to 210 days. The key findings are:
1) Both cultivars stored at 8°C showed higher accumulation of reducing sugars (glucose and fructose) compared to those stored at 12°C, leading to greater browning and poorer chip color at the lower temperature due to the Maillard reaction between sugars and proteins.
2) Sucrose levels initially decreased in both cultivars during the first 150 days of storage and then increased from 150-210 days, with the highest levels at 12
Effect of heat treatment, water activity and storage temperature on the oxida...Omar Zeballos
This document summarizes a study investigating the effects of heat treatment, water activity, storage temperature, and time on the oxidative stability of whole milk powder. Three types of milk powder (low-heat, medium-heat, and high-heat) were stored at two temperatures (25°C and 45°C) and three water activities for up to 63 days. Oxidative stability was assessed using electron spin resonance spectrometry to measure free radicals, TBARS to measure secondary lipid oxidation, fluorescent spectroscopy and size-exclusion HPLC to measure protein damage, and sensory evaluation. Results showed that lipid oxidation increased greatly at 45°C, especially for low-heat powder. Sensory quality declined fastest for low-heat powder stored at
The document summarizes the results of a study on the effect of storage period (0-60 days) on the physicochemical, sensory, and microbiological quality of bakery-flavored ice cream (containing cookies and cakes). Key findings include:
- Total solids, acidity, and specific gravity increased significantly with storage period, while pH, antioxidant activity, and overrun decreased significantly.
- Sensory attributes like appearance, texture, flavor, and overall acceptability significantly decreased with longer storage.
- First dripping time increased and melting rate decreased with storage period.
- Standard plate count and psychrophilic count increased significantly with storage period, indicating microbial deterioration.
This document discusses sperm cryopreservation, including the aims, techniques, factors affecting results, and future issues. The key points are:
- Sperm cryopreservation preserves sperm cells at sub-zero temperatures for future use, such as for fertility treatments. Slow freezing and rapid freezing are two common techniques.
- Factors like cryoprotectants, cooling/thawing rates, and semen quality can impact sperm survival after thawing. Semen preparation before freezing may improve outcomes.
- While some studies found cryopreservation does not affect reproductive success rates with ICSI, its effects on sperm DNA integrity are still unclear and require more research. Proper cryopreservation protocols aim to minimize DNA damage
Sperm cryopreservation is the process of freezing sperm to preserve fertility. It involves adding cryoprotective agents to minimize freezing damage before slowly cooling sperm to -196°C in liquid nitrogen storage. Factors like semen quality, freezing technique, and thawing process can impact sperm survival. While some studies found cryopreservation may damage DNA, properly performed it selectively affects defective sperm and clinical pregnancy rates are similar to fresh sperm. Optimization involves semen preparation, controlled freezing and thawing rates, and cryoprotectant use. Further research is still needed on impacts to DNA and reproductive outcomes.
The document discusses several current projects involving collagen and its applications. It describes developing a collagen-hydroxyapatite scaffold for bone defects, analyzing its pore size and efficacy. It also mentions exploring collagen-silver nanoparticle composites for wound care and using collagen coatings for tissue culture. Developing a hemostatic material using collagen and kaolin for heavy bleeding is also summarized.
This document analyzes the properties of sucrose crystals formed through nucleation of amorphous sucrose solutions. Differential scanning calorimetry was used to investigate how temperature affects the heat capacity of amorphous sucrose solutions and the mass, melting point, and density of recrystallized sucrose crystals. The heat capacities of amorphous sucrose solutions decreased with increasing temperature. The mass of recrystallized crystals varied between trials. Melting points of crystals were about 10°C lower than pure sucrose due to impurities. Densities of crystals were also lower than pure sucrose likely due to residual solution and dissolution during measurement.
This document discusses the effects of stabilizers on ice cream properties. Stabilizers increase mix viscosity and prevent wheying off and phase separation. They aid in suspension and produce a stable foam for packaging. Stabilizers also retard ice and crystal growth during storage fluctuations. They slow moisture migration and prevent shrinkage. Stabilizers provide uniformity and resistance to melting, producing a smooth texture. They decrease phase separation and control overrun. Stabilizers inhibit changes in air cells during storage and decrease melting rate by slowing serum drainage. They increase glass transition temperature and affect thermal conductivity. Hydrocolloid type and content influence flavor release and provide better creaminess and texture.
This presentation discusses cryopreservation of gametes. Cryopreservation is a process that uses very low temperatures, typically with liquid nitrogen at -196°C, to preserve living cells and tissues. Cryoprotective agents are used to protect cells from freezing damage. Techniques discussed include slow freezing, rapid freezing and vitrification. Applications include sperm banking, embryo freezing and ovarian tissue cryopreservation. Both benefits and limitations of cryopreservation are mentioned such as the ability to preserve biological materials long-term but also the risk of cell damage from ice formation or toxic effects of cryoprotectants.
- The quality of frozen foods is influenced by storage temperature, with quality decreasing as temperatures increase. Maintaining temperatures of -18°C is accepted as safe for extended shelf life.
- Temperature fluctuations during storage can cause recrystallization of ice crystals and reduce quality through increased crystal size.
- Factors like freezer burn, moisture migration, lipid oxidation, protein denaturation, and enzymatic browning can negatively impact the quality of frozen foods during storage and must be controlled. Understanding these factors is key to minimizing quality loss.
This document discusses a study on extending the shelf life of peach fruits. Peaches were harvested and dipped in aqueous solutions of 0%, 4%, or 6% calcium chloride for 10 minutes. The fruits were then cold stored at 0-2°C and 85-90% relative humidity for 3 weeks. Various quality parameters of the fruits like firmness, total soluble solids, weight loss, and sensory attributes were measured during cold storage and after storage at room temperature. The results showed that peaches dipped in 6% calcium chloride solution maintained acceptable quality for 3 weeks in cold storage and had a post-storage shelf life of 3 days at room temperature.
This document discusses the use of differential scanning calorimetry (DSC) to analyze various materials including ice melting points, specific heat capacity measurements of materials, starch gelatinization and retrogradation, protein denaturation, oil and fat crystallization, gel formation and melting, glass transition temperatures, and microbial growth measurements. DSC can be used to characterize many phase transitions and thermal properties of foods, polymers, and other materials.
Recent advances of starch based excipients used in extended-releasekarthickravi29
This document reviews recent advances in using modified starches as excipients in extended-release tablets. It discusses various starch derivatives used for this purpose, including retrograded starch, enzymatically modified starch, substituted starches like carboxymethyl starch and starch acetate, cross-linked starch, and grafted starch. Key factors influencing drug release from tablets containing these starches are summarized, such as crystalline structure, specific surface area, degree of substitution, and cross-link degree. The document concludes that physical or chemical modification and enzymatic hydrolysis can be used to control drug release from starch-based tablets by influencing gel formation and digestibility.
1. When milk is concentrated through evaporation, its viscosity increases due to a higher concentration of solids and proteins coagulating.
2. The sterilization process further increases viscosity, with low-temperature-long-time (LTLT) sterilization yielding a thicker product than high-temperature-short-time (HTST).
3. Viscosity decreases over time in storage, especially at higher temperatures, due to age thinning. Some milks may later increase in viscosity or even gel due to interactions between proteins and calcium/magnesium salts.
Potassium sorbate, sodium benzoate and citric acid together with vacuum packing have extended puree shelf life by 3-6 months in our trials at ambient conditions (T<25C).
However, the gap lies on the efficacy of the preservative combination in retarding or stopping the growth of harmful pathogens in the puree, and also their effects on β-carotene retention is unknown.
The document discusses a case study on the crystallization and stability of different crystal forms of the protein lysozyme. Specifically:
- Two crystal modifications of lysozyme (tetragonal and needle-shaped) were obtained and their phase diagrams and stability at different pH levels were analyzed.
- The solubility, crystal structures, and phase transition behavior of the two modifications were examined using various techniques like X-ray powder diffraction and microscopy.
- It was found that tetragonal crystals are more stable in acidic solutions while needle crystals are more stable in basic solutions, and the modifications can transition between each other under certain temperature and pH conditions.
Similar to Influences of temperature cycled storage on retrogradation and in (20)
2. Starch gelatinization is a process that disrupts the native molecular
orders of starch granules and typically occurs during thermal
processing in the presence of water.
Tends to re-associate to form an ordered gel-like structure which
ultimately induces changes in the physical behavior of the starch.
Starch often changes from an amorphous state to a crystalline state.
Retrogradation of starch during the storage of starch foods affects
the digestibility of starch and often decreases consumer acceptance
of starch-based foods such as bread, noodles or cooked rice.
Amylopectin contributes to the retrogradation occurring in long
term rheological and structural changes, whereas amylose is usually
responsible for the short-term, rapid changes in food texture.
Crystallization occurs in three consecutive steps: nucleation
(formation of critical nuclei), propagation (growth of crystals from
the nuclei formed) and maturation (crystal perfection or continuing
slow growth), all of which are temperature-dependent.
5/15/2016
3. Starch retrogradation increases the resistance of starch to digestive
enzymes and consequently reduces the GI value.
At a temperature near the starch glass transition, the nucleation rate of
starch crystallization is high and the propagation rate is low, whereas
the nucleation rate is low and the propagation rate is high when the
temperature is close to crystal melting.
Starch can be classified into three groups according to the rate of
glucose release and its absorption in the gastrointestinal tract: rapidly
digestible starch (RDS), slowly digestible starch (SDS) and resistant
starch (RS). RDS is the group of starches that can be rapidly
hydrolyzed by digestive enzymes; SDS is the group of starches that are
digested at a relatively slow rate and RS is the group of starches that
are not digested by digestive enzymes and are consequently transferred
into the colon.
5/15/2016
4. • waxy maize starch gels were retrograded under isothermal (4C) or
temperature cycles of 4 and 30C.
• We examined the starch recrystallization, crystalline structure and gel
texture, and digestibility of waxy maize starch gels to determine the
influences of storage conditions including the duration and
temperature cycle on starch retrogradation.
5/15/2016
5. Preparing of materials
Preparation of starch gels
Use of instrumental techniques for data analysing by:
A differential scanning calorimeter (DSC)
x- Ray diffraction of starch
In vitro digestibility the next slide shows the summarised
ways for this step.
5/15/2016
8. 5/15/2016
The onset temperature of melting retrograded starch molecules
increased from 30.6C to 34.4C as the storage time at the constant 4C
increased from 2 days to 16 days.
The peak temperature of the DSC endotherms gradually decreased
with extended storage time.
The melting enthalpy increased as the storage time increased,
indicating continuous propagation of starch recrystallization.
The gels stored under the temperature cycles of 4 and 30C showed
substantially greater onset temperature of melting retrograded starch,
this result may indicate that the homogeneity of retrograded starch
increases under temperature-cycled storage conditions.
9. 5/15/2016
The extended storage of waxy starch gel up to 16 days under cycled
temperature conditions led to an increased peak temperature
A decreased melting enthalpy was also observed with waxy maize
starch after a treatment at cycled temperatures of 6 and 40C.
During storage at 30C, possibly some of the unstable crystals that
melt at a relatively low temperature transformed to more stable
crystals
Starch gels stored at 4C showed a large increase in the enthalpy of
melting retrograded starch in the first 4 days of storage and leveled
off with further storage, whereas the melting enthalpy of the
retrograded starch in gels stored under the cycled temperatures
continuously increased
The cycled temperature storage appears to induce the formation of
more perfect and stable crystalsin the waxy starch gel
10. The glass transition temperature Tg of the freeze-concentrated
liquid phase in the starch gel increased and the enthalpy of ice
melting decreased during storage for 16 days.
The retrogradation of starch gel occurs through the association
of starch molecules during storage, reduces the mobility of
water molecules and decreases the amount of effective
plasticizing water. This change induces an increase in Tg and
the amount of freezable water.
Re-associations of starch molecules in the amorphous regions
occur primarily during the initial stage of storage where long
branches of amylopectin mainly contribute. This was verified
by the significant change in glass transition temperature in the
early stage of starch retrogradation.
Ice melting enthalpy was negatively related with Tg of the
freeze-concentrated liquid phase; an increase in Tg results in
decreased enthalpy for ice melting.
The starch gels stored under the cycled temperatures exhibited
a comparable increase in Tg and a much smaller decrease in ice
melting enthalpy than those stored under the 4C constant
temperature
5/15/2016
11. Storage of gel for 2 days induced no notable changes in X-ray
diffraction patterns, while a small increase in crystallinity was
observed after longer than 4 days of storage (data not shown).
The peak at 17° (2) indicates that the starch crystals formed in the
retrograded starch gel had the B-type configuration.
The B-type configuration is typical for retrograded starch. There
were no significant differences in X-ray patterns among starch gels
stored for different periods of time and temperature profiles.
5/15/2016
12. The hardness of the retrograded starch gel increased
during storage at a constant 4C for 16 days. However,
relatively few changes in hardness were observed
when the gel was stored under cycled temperatures of
4 and 30C for 16 days.
The hardness of starch gel stored at 4C increased
rapidly in the first 2 days of storage and the increase
slowed with further storage time. When stored
isothermally at 4C, the amorphous matrices of starch
gel may be continually transformed to more rigid
structures.
under cycled temperature storage, the amorphous
matrices formed at 4C were easily disrupted during
subsequent storage at 30C, preventing the hardening
of starch gel during storage.
When the starch gel was stored at 4C, the flexibility
increased in the first 2 days, and then decreased with
extended storage time despite the continuous increase
in hardness, the starch gels stored under cycled
temperatures were always softer than those stored
under the constant temperature of 4C.5/15/2016
13. The starch gelatinized increasing were 18.91%
and 81.09%, respectively.
With 2 days of storage at 4C, a substantial
decrease in the proportion of RDS of starch gel
and a concurrent increase in the proportion of
SDS were observed.
A significant decrease in the proportion of RDS
and an increase in the proportion of SDS were
observed with storage under a cycle of 4C for 2
days and 30C for 2 days.
The RS proportion consistently increased with
extended storage time for 16 days at the cycled
temperature conditions, along with decreases in
the proportions of SDS and RDS.
The starch gel stored for 16 days at the cycled
temperatures of 4 and 30C contained 48.2% RS,
whereas the gel stored for 16 days at constant 4C
had 10.3% RS.
Although the starch retrograded during storage
at 4C displayed a higher melting enthalpy than
those stored under the cycled conditions
The degree of starch crystallinity estimated by
DSC and X-ray diffraction may not effectively
explain the variations in the digestibility of the
retrograded starch gels.
5/15/2016
14. Both the kinetic constant (k) and the in vitro
glycemic index (GI) of retrograded starch gel
decreased as storage time increased.
The kinetic constant (k value) of starch digestion
sharply dropped in the first 4 days of storage,
indicating that a large portion of starch gel becomes
retrograded and indigestible.
The starch gels stored under the cycled temperatures
displayed lower k values than the gels stored at 4C.
(Fig. 3).
It was observed that the decrease in in vitro GI was
more substantial when the starch gel was stored at
the cycled temperatures, and the decrease continued
during storage for 16 days (Fig. 4). The continued
reduction in in vitro GI of the starch gel coincided
with the increased proportion of RS as the
temperature cycles were repeated.
Storage under the cycled temperatures of 4 and 30C
would be an effective way to reduce the digestion rate
and in vitro GI of starch-based foods.
5/15/2016
15. The differences in retrogradation behavior of starch molecules during storage under
the cycled temperatures resulted in a greater amount of RS content and lower value of
glycemic index.
The increase in gel hardness, which often results from the retrogradation of starch in
gels during storage, was effectively reduced when the gel was stored under the cycled
temperatures of 4 and 30C.
At conditions 4 , 30C, the starch crystals formed in the gel was melted at a higher onset
temperature with a narrower endothermic peak and a lower enthalpy than those
formed under constant temperature storage at 4C.
The glass transition temperature Tg increased and the ice melting enthalpy decreased
throughout the retrogradation process regardless of the temperature cycle.
The starch gel stored under the cycled temperature conditions shows slightly lower Tg
and greater ice melting enthalpy than those stored under the constant 4C.
The starch gel retrograded at the cycled temperature conditions remained softer than
those stored under constant temperature with similar flexibility, On the other hand, it
was a greater amount of resistant starch and reduced the in vitro glycemic index more
effectively than the isothermal storage condition.
5/15/2016