Hydrolysis and Fermentation of Pericarp and Endosperm Fibers Recovered from Enzymatic Corn Dry‐Grind Process

A modified dry‐grind corn process has been developed that allows recovery of both pericarp and endosperm fibers as coproducts at the front end of the process before fermentation. The modified process is called enzymatic milling (E‐Mill) dry‐grind process. In a conventional dry‐grind corn process, only the starch component of the corn kernel is converted into ethanol. Additional ethanol can be produced from corn if the fiber component can also be converted into ethanol. In this study, pericarp and endosperm fibers recovered in the E‐Mill dry‐grind process were evaluated as a potential ethanol feedstock. Both fractions were tested for fermentability and potential ethanol yield. Total ethanol yield recovered from corn by fermenting starch, pericarp, and endosperm fibers was also determined. Results show that endosperm fiber produced 20.5% more ethanol than pericarp fiber on a g/100 g of fiber basis. Total ethanol yield obtained by fermenting starch and both fiber fractions was 0.370 L/kg compared with ethanol yield of 0.334 L/kg obtained by fermenting starch alone.     

Relationships Between the Microstructure,Physical Features,and Chemical Composition of Different Maize Accessions from Latin America

Chemical composition (moisture, total lipids, protein, and apparent amylose) and some physical features (1,000 kernel weight, hardness, and anatomical composition) were determined in 71 accessions representing races of maize from Latin America. Their microstructural characteristics (size and compaction of endosperm cell bodies, pericarp thickness, horny‐floury endosperm ratio, and morphology and size of starch granules) were also evaluated using environmental scanning electron microscopy (ESEM). Compaction was the most important microstructural feature of the maize kernels, representing kernel hardness. Highly compact kernels tended to be hard, with high protein, pericarp, and hard‐endosperm content and high pericarp thickness, but with low moisture, amylose content, and kernel weight and size. The opposite was observed in the least compact kernels. Highly compact kernels tended to have small, polygonal starch granules (<10 μm), while the least compact kernels contained large, spherical granules (>10 μm). These results suggest that microstructure is responsible for the physical features of maize kernels and that microstructure is related to chemical composition.     

Physical characteristics of corn kernels as influenced by nitrogen fertilization

Abstract

Physical characteristics of corn (Zea mays L.) kernels influence end‐use. Agronomic practices including nitrogen (N) fertilization may influence kernel hardness. The objective of this study was to determine if com endosperm characteristics influence the effect of N fertilization on kernel hardness and breakage susceptibility. In 1988, six corn hybrids differing for endosperm were grown at two locations in Ohio and with two N rates (34 and 200 kg/ha). Kernels of the waxy hybrid were denser less susceptible to breakage than its near‐isogeneic normal counterpart. Soft kernels weighted less and were less dense than hard kernels, but these two hybrid classifications did not differ for breakage susceptibility. Hard kernels possessed a greater resistance to grinding than soft kernels. Increasing N fertilizer rate increased resistance to grinding and reduced susceptibility to breakage of both soft and hard endosperm types. Fertilization with N not only affects corn grain yield, but also affects physical characteristics that are important to end‐users.     

Effect of Broken Corn Levels on Water Absorption and Steepwater Characteristics

Broken corn created by grounding sound corn kernels was added back at levels of 0, 4, 8, 12, or 16%, by weight, to whole kernels of three corresponding hybrids: FR27 × FRMo17 (a soft endosperm corn), FR618 × FR600 (amedium‐hard endosperm corn), and FR618 × LH123 (a hard endosperm corn). The samples had been dried from 28% moisture content to 15% moisture content either by using ambient air at ≈25°C or at 110°C. Samples were steeped for 36 hr at 52°C in 0.15% sulfur dioxide and 0.5% lactic acid steeping solution. The steepwater characteristics, such as water absorption, solids and protein content in the steepwater, and steepwater pH, were measured by periodic sampling and analyzed. Broken corn level has a significant effect on the amount of solids released during steeping and steepwater protein content for all samples. Both steepwater solids and protein content increased linearly as broken corn content increased. Corn drying temperature, kernel hardness, and interactions between drying temperature and kernel hardness has a significant effect on steepwater solids and protein content and steepwater pH in both broken and unbroken corn. Corn dried at low temperature released more soluble solids and protein into the steepwater than corn dried at high temperature. Soft endosperm and medium‐hard endosperm corn released more soluble solids and protein into the steepwater than hard endosperm corn. Soft endosperm corn resulted in a higher steepwater pH than medium‐hard and hard endosperm corn. No significant effect of broken corn content on final moisture content of steeped corn and steepwater pH was observed.     

Cross‐Linked Resistant Starch: Preparation and Properties

Resistant starches (RS) were prepared by phosphorylation of wheat, waxy wheat, corn, waxy corn, high‐amylose corn, oat, rice, tapioca, mung bean, banana, and potato starches in aqueous slurry (≈33% starch solids, w/w) with 1–19% (starch basis) of a 99:1 (w/w) mixture of sodium trimetaphosphate (STMP) and sodium tripolyphosphate (STPP) at pH 10.5–12.3 and 25–70°C for 0.5–24 hr with sodium sulfate or sodium chloride at 0–20% (starch basis). The RS₄ products contain ≤100% dietary fiber when assayed with the total dietary fiber method of the Association of Official Analytical Chemists (AOAC). In vitro digestion of four RS₄ wheat starches showed they contained 13–22% slowly digestible starch (SDS) and 36–66% RS. However after gelatinization, RS levels fell by 7–25% of ungelatinized levels, while SDS levels remained nearly the same. The cross‐linked RS₄ starches were distinguished from native starches by elevated phosphorus levels, low swelling powers (≈3g/g) at 95°C, insolubilities (<1%) in 1M potassium hydroxide or 95% dimethyl sulfoxide, and increased temperatures and decreased enthalpies of gelatinization measured by differential scanning calorimetry.     

A Novel Modified Endosperm Texture in a Mutant High‐Protein Digestibility/High‐Lysine Grain Sorghum (Sorghum bicolor (L.) Moench)

Development of high‐protein digestibility (HPD)/high‐lysine (hl) sorghum mutant germplasm with good grain quality (i.e., hard endosperm texture) has been a major research objective at Purdue University. Progress toward achieving this objective, however, has been slow due to challenges posed by a combination of genetic and environmental factors. In this article, we report on the identification of a sorghum grain phenotype with a unique modified endosperm texture that has near‐normal hardness and possesses superior nutritional quality traits of high digestibility and enhanced lysine content. These modified endosperm lines were identified among F₆ families developed from crosses between hard endosperm, normal nutritional quality sorghum lines, and improved HPD/hl sorghum mutant P721Q‐derived lines. A novel vitreous endosperm formation originated in the central portion of the kernel endosperm with opaque portions appearing both centrally and peripherally surrounding the vitreous portion. Kernels exhibiting modification showed a range of vitreous content from a slight interior section to one that filled out to the kernel periphery. Microstructure of the vitreous endosperm fraction was dramatically different from that of vitreous normal kernels in sorghum and in other cereals, in that polygonal starch granules were densely packed but without the typically associated continuous protein matrix. We speculate that, due to the lack of protein matrix, such vitreous endosperm may have more available starch for animal nutrition, and possibly have improved wet‐milling and dry‐grind ethanol processing properties. The new modified endosperm selections produce a range that approaches the density of the vitreous parent, and have lysine content and protein digestibility comparable to the HPD/hl opaque mutant parent.     

Increasing Slowly Digestible Starch Content of Normal and Waxy Maize Starches and Properties of Starch Products

Changes in the digestibility and the properties of the starch isolated from normal and waxy maize kernels after heat‐moisture treatment (HMT) followed by different temperature cycling (TC) or isothermal holding (IH) conditions were investigated. Moist maize kernels were heated at 80°C for 2 hr. The HMT maize kernels were subjected to various conditions designed to accelerate retrogradation of the starch within endosperm cells. Two methods were used to accelerate crystallization: TC with a low temperature of –24°C for 1 hr and a high temperature of 20, 30, or 50°C for 2, 4, or 24 hr for 1, 2, or 4 cycles, and IH at 4, 20, 30, or 50°C for 24 hr. The starch granules were then isolated from the treated kernels. The starch isolated from HMT normal maize kernels treated by TC using –24°C for 1 hr and 30°C for 2 hr for 2 cycles gave the greatest SDS content (24%) and starch yield (54%). The starch isolated from HMT waxy maize kernels treated by TC using –24°C for 1 hr and 30°C for 24 hr for 1 cycle had an SDS content of 19% and starch yield of 43%. The results suggest that TC after HMT changes the internal structure of maize starch granules in a way that results in the formation of SDS (and RS). They also suggest that thermal treatment of maize kernels is more effective in producing SDS than is the same treatment of isolated starch. All starch samples isolated from treated normal maize kernels exhibited lower peak viscosities, breakdown, and final viscosities and higher pasting temperatures than did the control (untreated normal maize starch). Although peak viscosities and breakdown of the starch isolated from treated waxy maize kernels were similar to those of the control (untreated waxy maize starch), their pasting temperatures were higher. The starch isolated from treated normal and waxy maize kernels with the highest SDS contents (described above) were further examined by DSC, X‐ray diffraction, and polarized light microscopy. Onset and peak temperatures of gelatinization of both samples were higher than those of the controls. Both retained the typical A‐type diffraction pattern of the parent starches. The relative crystallinity of the starch from the treated normal maize kernels was higher than that of the control, while the relative crystallinity of the starch from the treated waxy maize kernels was not significantly different from that of the control. Both treated starches exhibited birefringence, but the granule sizes of both starches, when placed in water, were slightly larger than those of the controls.     

Single Kernel Sampling Method for Maize Starch Analysis While Maintaining Kernel Vitality

A nondestructive protocol for maize kernel starch sampling was developed, enabling starch preparation from a single kernel for analysis of starch structure while also maintaining the vitality of the seed. To develop the single kernel sampling (SKS) method, maize genotypes varying in starch structure including ae, wx, su2, du and normal in the W64A inbred line were used. Crude endosperm material was removed from the kernel crown, soaked, ground, washed, and dissolved in 90% DMSO. The sample represented ≈10% of the total kernel. Endosperm starch was also isolated from the same genotypes by a standard multikernel isolation (MKI) method. Starches isolated by the two methods were debranched and analyzed by high‐performance size‐exclusion chromatography (HPSEC) and fluorophore‐assisted carbohydrate electrophoresis (FACE). HPSEC and FACE showed similar results for the two sampling methods for degree of polymerization (DP) ≤ 50. We concluded that the material obtained by SKS could be used for identifying amylopectin structural differences among genotypes. Kernel sampling for SKS had no effect on germination, thus plants could be grown for subsequent genetic crosses and analysis. The SKS method may be useful for the screening of populations of maize kernels from genotypes producing novel amylopectin structure, and allow the growth of novel genotypes for further analysis.     

Kernel Microstructure of Latin American Races of Maize and Their Thermal and Rheological Properties

Seventy‐one races of maize representing races from Latin America were analyzed for microstructural features such as the degree of compaction of the endosperm cell bodies, starch granule size and morphology, and hard‐soft endosperm relationship. Flours were analyzed using rapid visco analysis and differential scanning calorimetry. Compaction grade was the most important microstructural feature of the maize kernels that related to thermal and rheological properties. Highly compact kernels developed low peak and final viscosities; small, polygonal starch granules; and required more time and higher temperature to gelatinize. The opposite was the case for less compact kernels. This indicates that the characteristic protein matrix of highly compact kernels represents a physical barrier to water migration into the granules, retarding the gelatinization process.     

Physical and Milling Characteristics of Wheat Kernels After Enzyme and Acid Treatments

The current wheat milling process separates bran from endosperm by passing tempered wheat kernels through successive break rolls and sifters. Using hydrolytic enzymes during tempering degrades bran and aleurone layers and can improve milling efficiency and yield. This study was conducted to evaluate the effects of chemical and enzymatic treatments of wheat kernels before milling on physical and milling characteristics of the resulting wheat and flour quality. Hard wheat kernels were soaked in dilute acid or water and dried back to original moisture before being tempered with enzymes in water. Kernel physical and milling characteristics (600 g) were evaluated. Dilute acid soaking did not affect the 1,000‐kernel weight and diameter but softened treated kernels. When treated kernels were pearled, bran removal was mostly from ends; and the reducing sugar content in enzyme‐treated bran was significantly higher than the control. Compared with the control, acid‐soaked enzyme‐tempered kernels showed small but significant improvement in straight flour yield, with virtually no difference in protein content, and flour color. Chemical and enzyme treatment resulted in higher ash in flour. These differences were not seen in milling of larger batches (1,500 g) of kernels.     

Importance of Protein‐Rich Components in Emulsifying Properties of Corn Fiber Gum

Purified corn fiber gum (CFG‐F) isolated from fine (kernel endosperm‐derived) corn fiber that contained ≈2% residual protein was extracted with 70% aqueous ethanol. The aqueous ethanol extract (AEE), which contained 19.5% of the total CFG, contained a high percentage of the proteinaceous material present in the original gum sample. The AEE gum contained 6.81% protein by weight. The residue (R), which constituted 66% of the total CFG‐F, contained only 0.55% of protein. The emulsifying properties of R and AEE in a model oil‐in‐water emulsification system were studied by measuring turbidity after 1, 2, and 3 weeks, particle size after 4 weeks, and by confocal laser scanning microscopy after three months of storage at room temperature. These gums were compared with the standard well‐known emulsifiers native acacia gum (NAG) and modified acacia gum (MAG). The results indicate that although AEE contains protein‐rich components, it is not as good an emulsifier as the residue which contains only 0.55% of protein. However, emulsions prepared with the whole (unfractionated) CFG‐F under similar conditions were more stable showing higher turbidity and smaller particles size than those prepared with either R or AEE.     

Protease Treatment to Improve Ethanol Fermentation in Modified Dry Grind Corn Processes

To improve fractionation efficiency in modified dry grind corn processes, we evaluated the effectiveness of protease treatment in reducing residual starch in endosperm fiber. Three schemes of protease treatment were conducted in three processes: 1) enzymatic milling or E‐Mill, 2) dry fractionation with raw starch fermentation or dry RS, and 3) dry fractionation with conventional fermentation or dry conv. Kinetics of free amino nitrogen production were similar in both dry and wet fractionation (E‐Mill), indicating that proteolysis was effective in all three schemes. At the end of fermentation, endosperm fiber was recovered and its residual starch measured. Using protease treatment, residual starch in the endosperm fiber was reduced by 1.9% w/w (22% relative reduction) in dry conv and 1.7% w/w (8% relative reduction) in dry RS, while no reduction was observed in the E‐Mill process. Protease treatment increased ethanol production rates early in fermentation (≤24 hr) but final ethanol concentrations were unaffected in both dry RS and E‐Mill. In dry conv, the addition of protease resulted in a decline in final ethanol concentration by 0.3% v/v, as well as a higher variability in liquefaction product concentration (higher standard deviations in the glucose and maltose yields). Protease treatment can be used effectively to enhance modified dry grind processes.     

Corn Endosperm Fermentation Using Endogenous Amino Nitrogen Generated by a Fungal Protease

Fractionating the corn kernel to separate endosperm from germ and pericarp improves corn ethanol processing by increasing fermentation throughput and generating salable coproducts. One fractionation technology, dry fractionation (DF), suffers from loss of germ‐derived nutrients and amino acids, resulting in poor fermentation performance. Such deficiencies may be addressed by increasing nitrogen and other nutritional supplementation. As an alternative to exogenous nitrogen source, we investigated the use of a fungal protease to generate free amino nitrogen (FAN) from corn endosperm. Incubation of endosperm with protease did not affect subsequent liquefaction and saccharification. FAN supplementation through proteolysis resulted in fermentation being 99% complete in 48 hr, compared to 93% maximum with urea supplementation. Viable cell growth rates were similar in FAN and urea‐supplemented fermentations. Urea and FAN addition resulted in similar fermentation characteristics and similar FAN consumption rates as with FAN alone, which was indicative that FAN was assimilated preferentially. Increased amounts of maltose remaining after fermentation were correlated with initial FAN concentrations in mash. This observed trend was implicated in ethanol yield reduction of 2 g/L at high protease loading (generating 1.6 mg of FAN/g of glucose substrate) compared to a urea control. Using a glucose and maltose solution, we confirmed higher residual maltose in fermentations supplemented with high FAN concentrations. Use of protease to generate optimal FAN concentration in mash (1.2 mg of FAN/g of glucose substrate) could improve economics of dry fractionated corn ethanol production by increasing fermentation rates and, consequently, reducing fermentation time.     

玉米应力裂纹的显微分析

观察了３种应力裂纹类型（单裂、双裂、龟裂）玉米的内部显微结构和应力裂纹产生的位置、数量、宽度，分析了应力裂纹在胚乳中扩展的情况以及应力裂纹对胚乳结构产生的影响。裂纹的类型不同，裂纹的形态、数量及大小亦不同。应力裂纹生成在粉质胚乳的中心部位，沿淀粉颗粒的边缘向外扩展。应力裂纹是内部裂纹，只能扩展到种皮附近，接近糊粉层。     

Rapid Screening to Identify Unusual Thermal Starch Traits from Bulked Corn Kernels

Differential scanning calorimetry (DSC) is used routinely to screen for starch thermal properties. In early generations of line development, the established analysis separately evaluates starch extracted from five, single corn kernels. A thermal property trait carried by a recessive gene would appear 25% of the time; thus, if five separate kernels were evaluated, the likelihood of detecting an unusual thermal trait is high. The objective of the current work was to expedite selection by examining five kernels at a time, instead of one, hypothesizing that we would be able to detect different thermal properties in this blend. Corn lines, all from the same genetic background (ExSeed68 or Oh43), with known thermal functions (amylose‐extender, dull, sugary‐1, sugary‐2, and waxy) were blended with normal starch (control) in ratios of 0:5, 1:4, 2:3, 3:2, 4:1, and 5:0, and analyzed with DSC. The values for each ratio within a mutant type were unique (α < 0.01) for most DSC measurements, especially for gelatinization onset temperature, change in enthalpy of gelatinization, and range of gelatinization. These results support the five‐kernel method for rapidly screening large amounts of corn germplasm to identify kernels with unusual starch traits.     

Ethanol Production from Modified and Conventional Dry‐Grind Processes Using Different Corn Types

Different corn types were used to compare ethanol production from the conventional dry‐grind process to wet or dry fractionation processes. High oil, dent corn with high starch extractability, dent corn with low starch extractability and waxy corn were selected. In the conventional process, corn was ground using a hammer mill; water was added to produce slurry which was fermented. In the wet fractionation process, corn was soaked in water; germ and pericarp fiber were removed before fermentation. In the dry fractionation process, corn was tempered, degerminated, and passed through a roller mill. Germ and pericarp fiber were separated from the endosperm. Due to removal of germ and pericarp fiber in the fractionation methods, more corn was used in the wet (10%) and dry (15%) fractionation processes than in the conventional process. Water was added to endosperm and the resulting slurry was fermented. Oil, protein, and residual starch in germ were analyzed. Pericarp fiber was analyzed for residual starch and neutral detergent fiber (NDF) content. Analysis of variance and Fisher's least significant difference test were used to compare means of final ethanol concentrations as well as germ and pericarp fiber yields. The wet fractionation process had the highest final ethanol concentrations (15.7% v/v) compared with dry fractionation (15.0% v/v) and conventional process (14.1% v/v). Higher ethanol concentrations were observed in fractionation processes compared to the conventional process due to higher fermentable substrate per batch available as a result of germ and pericarp fiber removal. Germ and pericarp yields were 7.47 and 6.03% for the wet fractionation process and 7.19 and 6.22% for the dry fractionation process, respectively. Germ obtained from the wet fractionation process had higher oil content (34% db) compared with the dry fractionation method (11% db). Residual starch content in the germ fraction was 16% for wet fractionation and 44% for dry fractionation. Residual starch in the pericarp fiber fraction was lower for the wet fractionation process (19.9%) compared with dry fractionation (23.7%).     

Evaluation and Strategies to Improve Fermentation Characteristics of Modified Dry‐Grind Corn Processes

New corn fractionation technologies that produce higher value coproducts from dry‐grind processing have been developed. Wet fractionation technologies involve a short soaking of corn followed by milling to recover germ and pericarp fiber in an aqueous medium before fermentation of degermed defibered slurry. In dry fractionation technologies, a dry degerm defiber (3D) process (similar to conventional corn dry‐milling) is used to separate germ and pericarp fiber before fermentation of the endosperm fraction. The effect of dry and wet fractionation technologies on the fermentation rates and ethanol yields were studied and compared with the conventional dry‐grind process. The wet process had the highest fermentation rate. The endosperm fraction obtained from 3D process had lowest fermentation rate and highest residual sugars at the end of fermentation. Strategies to improve the fermentation characteristics of endosperm fraction from 3D process were evaluated using two saccharification and fermentation processes. The endosperm fraction obtained from 3D process was liquefied by enzymatic hydrolysis and fermented using either separate saccharification (SS) and fermentation or simultaneous saccharification and fermentation (SSF). Corn germ soak water and B‐vitamins were added during fermentation to study the effect of micronutrient addition. Ethanol and sugar profiles were measured using HPLC. The endosperm fraction fermented using SSF produced higher ethanol yields than SS. Addition of B‐vitamins and germ soak water during SSF improved fermentation of 3D process and resulted in 2.6 and 2.3% (v/v) higher ethanol concentrations and fermentation rates compared with 3D process treatment with no addition of micronutrients.     

Maize Proximate Composition and Physical Properties Correlations to Dry‐Grind Ethanol Concentrations

Dry‐grind ethanol plants incur economic losses because of seasonal variations in ethanol yields. One possible cause associated with ethanol yield variability is incoming grain quality. There is little published information on factors causing variation in dry‐grind ethanol concentrations. The objective of this study was to determine relationships between rapidly measurable corn quality attributes (physical parameters and chemical composition) and dry‐grind ethanol concentrations. Corn samples obtained from a Midwestern ethanol plant were analyzed for physical quality parameters (test weight, kernel weight, true density, percent stress cracks, and moisture content) and composition (starch, protein, oil, and soluble sugars contents) and then processed with a laboratory‐scale dry‐grind procedure. There were significant (P < 0.05) variations in corn quality parameters and ethanol concentrations. Correlation coefficients were significant (P < 0.05) but low (–0.50 < r < 0.50) between starch content and final ethanol concentrations (72 h) and total soluble sugar content and ethanol concentrations at 72 and 48 h. Ethanol concentrations (at 24, 48, and 72 h) were predicted as a function of a combination of grain quality factors using multiple regression methods; however, the R² values obtained were low. Variations in ethanol concentrations were not related to physical and chemical composition quality factors. Other factors, such as structural and physiologic attributes of corn grain, need to be evaluated.     

Factors Affecting the Alkaline Cooking Performance of Selected Corn and Sorghum Hybrids

Dent corn (Zea mays L.) and sorghum (Sorghum bicolor L. Moench) sample sets representative of commonly grown hybrids and diverse physical attributes were analyzed for alkaline cooking performance. The influence of kernel characteristics including hardness, density, starch properties (thermal, pasting, and crystallinity), starch content, protein content, and prolamin content on alkaline cooking performance was also determined. Corn nixtamal moisture content was lower for hard, dense kernels with high protein contents; sorghum nixtamal moisture content was lower for kernels with low moisture contents and low starch relative crystallinities. Statistically significant (P < 0.05) regression equations showed that corn nixtamal moisture content was influenced by TADD (tangential abrasive dehulling device) index, kernel moisture content, starch content, and protein content; sorghum nixtamal moisture content was influenced by starch relative crystallinity, kernel moisture content, and abrasive hardness index. Pericarp removal was not strongly correlated with kernel characterization tests. Location (environmental) and hybrid (genetic) factors influenced most kernel characteristics and nixtamalization processing variables.     

Capillary Rheometry of Corn Endosperm: Glass Transition,Flow Properties,and Melting of Starch

A capillary rheometer was manufactured to study the properties of corn endosperm. Samples were tested at or near the pressures and temperatures encountered in high-temperature, short-time extrusion. The rheometer was designed to prevent moisture loss during testing. At a set pressure, raising the temperature caused corn endosperm particles to soften and change shape, resulting in a pressure drop as the voids in the sample were reduced. The temperature at which the pressure drop occurred was considered the glass transition temperature. Continued heating caused the pressure to rise and drop a second time as the sample softened and flowed through the capillary. Thermal analysis by differential scanning calorimetry showed that complete melting of starch crystals was not necessary to permit capillary flow. Pressure and temperature conditions sufficient to initiate flow were measured for opaque and vitreous corn flours and expressed as a boundary curve defining the flow region. The position of the curve shifted as a function of sample moisture content. The vitreous corn sample had a rough (unstable) flow that could be eliminated by addition of a small amount (2% w/w) of vegetable oil. When isolated corn starch was studied in the capillary rheometer, results showed that, under certain conditions, starch crystal melting was affected by pressure and time. A model was developed to account for the effects of pressure, temperature, time, and sample moisture on starch crystal melting.