Influence of physicochemical interactions between amylose and aroma compounds on the retention of aroma in food-like matrices

In food matrices, where starch is often used as a gelling or texturing agent, the occurrence of amylose-aroma complexes and their effect on the release of aroma compounds are difficult to determine. Indeed, thick or gelled systems are known to reduce the diffusion rate of flavor molecules, resulting in an increase of retention. Moreover, interactions between aroma compounds and matrix components might increase the retention of aroma compounds. The complexing behavior of three aroma compounds with amylose was studied by DSC and X-ray diffraction to determine the relative importance of these two factors. Their interaction properties were different: two of them formed complexes, and the third did not. These aroma compounds were added in food matrices containing different starches that induced different textures. Their retention was studied by static headspace analysis. The retention of aroma compounds appeared to depend on the amylose/amylopectin ratio of starch, both from the formation of complexes and by a viscosity effect.     

Retention of aroma compounds in starch matrices: competitions between aroma compounds toward amylose and amylopectin

The retention of three aroma compounds-isoamyl acetate, ethyl hexanoate, and linalool--from starch-containing model food matrices was measured by headspace analysis, under equilibrium conditions. We studied systems containing standard or waxy corn starch with one or two aroma compounds. The three studied aroma compounds interact differently: ethyl hexanoate and linalool form complexes with amylose, and isoamyl acetate cannot. However, in systems containing one aroma compound, we observed with both starches a significant retention of the three molecules. These results indicate that amylopectin could play a role in the retention of aroma. In systems containing two aroma compounds in a blend, the retentions measured for isoamyl acetate and for linalool were either equal to or less than those in systems where they were added alone. This phenomenon was attributed to competition between aroma compounds to bind with starch. The retention of aroma compounds blended in starch-based systems gave us additional information which confirmed that interactions occur not only with amylose but also with amylopectin.     

Release of isoamyl acetate from starch pastes of various structures: thermodynamic and kinetic parameters

The release of isoamyl acetate from starch-based matrices was studied on the basis of a cumulative dynamic headspace analysis. Two corn starches were compared, which are known to yield pastes and gels differing in their structures and properties. These properties were assessed by viscometry and viscoelastic measurements. Aroma release was discussed as a function of the structure and texture parameters of the matrix.The release curves obtained from water and from the various starch-based matrices at 25 degrees C showed similar patterns but differed in their initial slopes and in the final plateau values. The lowest initial slopes were obtained for the normal starch dispersions that formed gels due to amylose gelation. The aroma compound was entirely released from water and from the waxy starch pastes. A significant amount of isoamyl acetate remained trapped in the normal starch dispersions.     

Behavior of flavor compounds in model food systems: a thermodynamic study

Physicochemical parameters, such as hydrophobicity, water solubility, and volatility, of four flavor compounds (ethyl acetate, ethyl butyrate, ethyl hexanoate, and 2-pentanone) were determined. The amount of flavor compounds released from different model matrices (mineral water, purified triolein, an oil-in-water emulsion, a carbohydrate matrix, and a complex matrix containing lipids and carbohydrates) into the gaseous phase was determined at thermodynamic equilibrium, at 37 degrees C, by static headspace gas chromatography. The degree of interaction between the flavor compounds and the matrix components was shown by measuring the percentage retention using the water matrix as the reference. The partition of flavor compounds was principally dependent on their hydrophobicity. Physicochemical interactions that occurred in the different media led to different degrees of flavor retention. An impact of fat on flavor retention was demonstrated when a water matrix and an oil-in-water matrix or carbohydrate and complex matrices were compared. A carbohydrate impact on flavor compound retention was also detected, which was evident even in the presence of lipids.     

基于岭脊分析的藜麦淀粉提取及糊化特性研究

为优化藜麦淀粉碱法提取工艺,以藜麦为试验材料,采用岭脊分析法研究料液比、NaOH 质量分数和浸提时间对淀粉提取率的影响,并对藜麦淀粉的颗粒形貌、化学结构及淀粉糊化特性进行研究。结果表明,碱法提取藜麦淀粉的优化工艺参数为料液比1：5 g/mL、NaOH质量分数0.2%和浸提时间5.5 h,淀粉提取率为98.94%±0.26%;藜麦淀粉为限制性膨胀淀粉,形态多呈不规则形,具有-OH、-CH2、-CHO、C-O-C和吡喃环典型淀粉分子官能团;随静置时间增加,淀粉透光率降低,凝沉体积增加,12 h后基本稳定;藜麦淀粉糊第四次冻融循环后达到稳定状态;对淀粉凝胶质构特性分析,硬度、内聚性、弹性、胶黏性和咀嚼性5个指标都随藜麦淀粉糊浓度增加而增大;流变性分析表明藜麦淀粉糊为假塑性流体,其弹性优于黏性。该文系统研究藜麦淀粉提取工艺和糊化特性,拓展了新的淀粉资源,同时也为藜麦淀粉的生产和应用提供一定的借鉴和参考。     

Starch Participation in Durum Dough Linear Viscoelastic Properties

The contribution of starch to dough rheological properties has been largely overshadowed by the role of gluten, receiving much less attention in comparison. The influence of starch granule surface properties on durum wheat dough linear viscoelasticity was investigated, and surface interactions between starch granules and gluten were assessed using a model system. Proportions of starch were substituted in dough on a volume basis with an inert filler (glass powder) with a similar particle size range. The doughs were subjected to dynamic and creep measurements. Dough linear viscoelastic properties were weakened on substitution of starch with glass powder at ≤50% substitution, inferring a reduction in adhesion at the matrix‐filler (starch and glass powder) interface with declining proportions of starch granules. Surface modification of starch granules or glass powder altered dough rheological properties, confirming the importance of starch granule surface characteristics and the nature of protein‐starch bonding on durum dough linear viscoelastic behavior.     

Uptake of Cu2+ by starch granules as affected by counterions

Potato and wheat starch granules were soaked in 1% aqueous solutions of copper(II) salts: acetate, chloride, and sulfate. Such treatment caused sorption of Cu(2+) ions at the granule surface and their penetration into the granule interior as was proven, for sectioned granules of investigated starch, by scanning electron microscopy combined with an X-ray microanalysis system (energy dispersive spectroscopy). Copper ions incorporated into the granules influenced the starch thermal stability. Uptake of Cu(2+) by potato, determined by flame atomic absorption spectrometry, was much higher than obtained for the wheat starch. Moreover, it was dependent on copper counteranions present in the solution. In all investigated granules, the most effective sorption occurred in the acetate solution. Starch dehydration or/and freezing and thawing, affecting the water-dependent inner structure of the granules, also influenced the amount of Cu(2+) taken from the solutions. Thus, compared to that in native starch, this value was considerably higher in Cu(CH 3COO)2, almost unchanged in CuSO4, and significantly lower in the case of CuCl2 solution. The influence of chloride and sulfate anions seemed to correlate with their water structure-making and structure-breaking ability, affecting the migration of Cu(2+) in the amorphous parts of the granules. However, high Cu uptake observed for acetate solution could be explained on the basis of acetate anion hydrolysis activating the polysaccharide matrix for cation binding. The obtained results provide new information about interactions of starch granules with salt solution and therefore support our understanding of starch properties.     

Effect of pH on retention of aroma compounds by beta-lactoglobulin

Interactions between volatile compounds and BLG in aqueous solution were studied using static and dynamic headspace techniques (exponential dilution). The intensity of interactions between methyl ketones (C7-C9), ethyl esters (C6-C9), limonene, myrcene, and beta-lactoglobulin (BLG) were estimated by determination of the relative infinite dilution activity coefficients (gamma(r)). For a constant pH value, the methyl ketones retention by BLG increased significantly with the hydrophobicity of the volatiles, whereas the retention reached a maximum for ethyl octanoate in the ester series, indicating a possible steric hindrance. For limonene and myrcene an unexpected increase in headspace concentration or "salting out" effect was noticed for acid pH. The variations of the retention according to the pH increase of the medium from pH 3 to pH 11 could be related to structural modifications of the BLG. The retention increase observed between pH 3 and pH 9 resulted from the flexibility modification of the protein, allowing better accessibility to the primary or the secondary hydrophobic sites, whereas the dramatic decrease observed at pH 11 was the consequence of the alkaline denaturation of BLG. Electrostatic interactions occurring at pH 7.5 could also explain the observed retention increase.     

Effect of Lime on Gelatinization of Corn Flour and Starch

Analysis of swelling power, water retention capacity, and degree of gelatinization of corn flour cooked in water with and without lime indicated, over a concentration range of 0–1% (w/v), that at low concentrations, lime increases swelling and digestibility of starch granules. Measurement of starch solubility revealed an increase in the amount of starch dissolved by lime cooking. Swelling, retention, and gelatinization exhibited maxima at or near 0.2% (w/v) lime, and then decreased as lime concentration increased. Hot-stage polarized light microscopy and differential scanning calorimetry of isolated starch revealed increasing gelatinization temperatures with increasing lime concentrations. It is hypothesized that the high pH of the system causes starch hydroxyl groups to ionize, thereby creating binding sites for Ca⁺⁺/CaOH⁺ and producing Ca-starch crosslinks. It is also suggested that, at low lime levels (<0.4%, w/v), granule crystalline regions are disrupted and the granule matrix is stretched by exchange of protons for calcium ions; when the lime level surpasses 0.4% (w/v), the granule shell becomes stabilized by Ca⁺⁺-starch interactions, producing stronger, more rigid granules.     

Headspace solid-phase microextraction method for the study of the volatility of selected flavor compounds

Changes in the volatility of selected flavor compounds in the presence of nonvolatile food matrix components were studied using headspace solid-phase microextraction (HS-SPME) combined with GC-MS quantification. Time-dependent adsorption profiles to the SPME fiber and the partition coefficients between different phases were obtained for several individual volatiles, showing that HS-SPME analysis with a short sampling time can be used to determine the "true" headspace concentration at equilibrium between the headspace and a sample matrix. Equilibrium dialysis followed by HS-SPME/GC-MS was carried out to confirm the ability of HS-SPME extraction for monitoring the free volatile compounds in the presence of proteins. In particular, a short sampling time (1 min) avoided additional extraction of volatiles bound to the protein. Interactions between several selected flavor compounds and nonvolatile food matrix components [beta-lactoglobulin or (+)-catechin] were also studied by means of HS-SPME/GC-MS analysis. The volatility of ethyl hexanoate, heptanone, and hexanal was significantly decreased by the addition of beta-lactoglobulin compared to that of isoamyl acetate. Catechin decreased the volatility of ethyl hexanoate and hexanal by 10-20% and increased that of 2-heptanone by approximately 15%. This study indicates that HS-SPME can be a useful tool for the study of the interactions between volatile compounds and nonvolatile matrix components provided the kinetic and thermodynamic behavior of the volatiles in relation to the fiber chosen for the studies is carefully considered.     

Enzymatic Hydrolysis of Barley Starch Lipids

The efficiency of phospholipase and lipase preparations in the hydrolysis of lysophospholipids of native and gelatinized barley starch was examined. The degree of hydrolysis was analyzed by determination of the amount of released fatty acids by an enzymatic method. Thermal and structural properties of the enzyme-treated starch were studied by differential scanning calorimetry and light microscopy. Lysophospholipids of the gelatinized barley starch were easily hydrolyzed, in contrast to the lipids of the granular starch. The maximum degree of hydrolysis achieved for the gelatinized starch was 80% and for the native starch ≈20%. Gelatinization enthalpies and micrographs indicated that even though the amount of the released fatty acids from the native starch was small, formation of free fatty acids inhibited swelling and gelatinization of starch granules.     

Structural properties of hydrolyzed high-amylose rice starch by α-amylase from Bacillus licheniformis

High-amylose cereal starch has a great benefit on human health through its resistant starch (RS) content. Enzyme hydrolysis of native starch is very helpful in understanding the structure of starch granules and utilizing them. In this paper, native starch granules were isolated from a transgenic rice line (TRS) enriched with amylose and RS and hydrolyzed by α-amylase. Structural properties of hydrolyzed TRS starches were studied by X-ray powder diffraction, Fourier transform infrared, and differential scanning calorimetry. The A-type polymorph of TRS C-type starch was hydrolyzed faster than the B-type polymorph, but the crystallinity did not significantly change during enzyme hydrolysis. The degree of order in the external region of starch granule increased with increasing enzyme hydrolysis time. The amylose content decreased at first and then went back up during enzyme hydrolysis. The hydrolyzed starches exhibited increased onset and peak gelatinization temperatures and decreased gelatinization enthalpy on hydrolysis. These results suggested that the B-type polymorph and high amylose that formed the double helices and amylose-lipid complex increased the resistance to BAA hydrolysis. Furthermore, the spectrum results of RS from TRS native starch digested by pancreatic α-amylase and amyloglucosidase also supported the above conclusion.     

Influence of Cooking Conditions on the Protein Matrix of Sorghum and Maize Endosperm Flours

To understand the influence of the sorghum and maize endosperm protein matrix honeycomb structure on starch hydrolysis in flours, three‐dimensional fluorescence microscopy was applied to floury and vitreous endosperm flours cooked under various conditions. Cooking caused the collapse and matting of the sorghum and maize vitreous endosperm matrices, with the effect being greater in sorghum. The effect of cooking was rather different in the floury endosperm in that the protein matrices expanded and broke up to some extent. These effects were a consequence of expansion of the starch granules through water uptake during gelatinization. Cooking in the presence of 2‐mercaptoethanol caused an expansion of the vitreous endosperm matrix mesh due to breakage of disulfide bonds in the protein matrix. Mercaptoethanol also caused an increase in the proportion of β‐sheet structure relative to α‐helical structure of the endosperm proteins. Increased energy of cooking caused collapse of the sorghum matrix. Disulfide bonding and an increase in β‐sheet structure occurred with cooking, with the increase in disulfide bonding being greatest in sorghum vitreous endosperm. The tendency for the sorghum protein matrix to collapse and mat more with cooking than the maize matrix appears to be due to greater disulfide bonding. This is responsible for the observed low starch digestibility of cooked sorghum flour as a result of the more disulfide‐bonded protein matrix limiting the expansion of the starch granules and hence amylase access.     

Cycloamylose (cyclodextrin) glucanotransferase degrades intact granules of potato raw starch

Cycloamylose (cyclodextrin) glucanotransferase (EC 2.4.1.19, CGTase) originated from Bacillus macerans degraded intact granules of potato raw starch and converted them into cyclodextrins (CDs). The degradation required sufficient stirring of starch-CGTase suspension. The morphology of the degraded starch granules was unique; that is, the inner part of the granules was observed by scanning electron microscope to be more susceptible to CGTase than the outer part. Effects of pH, temperature, starch concentration, and enzyme amount on CD production were studied.     

Model studies on retention of added volatiles during breadcrumb production

Breadcrumb samples were prepared with a range of volatile compounds at known concentrations. The retention of these volatiles was assessed via solvent extraction and quantification by gas chromatography-mass spectrometry. Volatile loss during processing was shown to be substantial and dependent upon the compound's vapor pressure. The influence of initial concentration levels on the retention of volatiles was linear within the bounds of the experimental concentrations (0-300 mg/kg). Comparison of volatile concentration at various stages throughout the production process (by headspace analysis) showed that the greatest losses occurred during the processing stages that involved heat, namely, microwave heating and drying. The production of samples by freeze drying showed an increased average retention of 17% as compared to fluidized bed drying and flat bed drying, which showed the highest volatile losses.     

气流粉碎对玉米淀粉结构及理化性质的影响

为研究气流粉碎对玉米淀粉结构及理化性质的影响,该文以普通玉米淀粉为原料,通过流化床气流粉碎处理,采用扫描电子显微镜、偏光显微镜、粒度分析仪、X-射线衍射仪、红外光谱仪、差示扫描量热仪、快速黏度分析仪等分析手段研究经微细化处理前后玉米淀粉颗粒形貌、晶体结构、热力学特性、糊化特性、溶解度和膨胀度、冻融稳定性、持水能力等结构及性质的变化。结果表明,微细化处理后,淀粉颗粒形变的不规则,粒径明显减小,中位径(D50)由14.37μm减小到5.25μm,偏光十字减少,相对结晶度由33.43%降低至15.46%,淀粉颗粒结晶结构被破坏,由多晶态向无定形态转变,粉碎过程淀粉无新的基团产生;热焓值、糊化温度均降低,热糊稳定性好;溶解度、膨胀度均升高,持水能力增加,冻融稳定性好,产生较好的热糊稳定性和冷糊力学稳定性,该研究为玉米淀粉的深度加工与应用提供了理论依据及技术支撑。     

Resistant Starch Escaped from Ethanol Production: Evidence from Confocal Laser Scanning Microscopy of Distiller's Dried Grains with Solubles (DDGS)

The origin of resistant starch (RS) in distiller's dried grains with solubles (DDGS) of triticale, wheat, barley, and corn from dry‐grind ethanol production was studied. A considerable portion of starch (up to 18% in DDGS) escaped from either granular starch hydrolysis or conventional jet‐cooking and fermentation processes. Confocal laser scanning microscopy revealed that some starch granules were still encapsulated in cells of grain kernel or embedded in protein matrix after milling and were thus physically inaccessible to amylases (type RS1). The crystalline structures of native starch granules were not completely degraded by amylases, retaining the skeletal structures in residual starch during granular starch hydrolysis or leaving residue granules and fragments with layered structures after jet‐cooking followed by the liquefaction and saccharification process, indicating the presence of RS2. Moreover, retrograded starch molecules (mainly amylose) as RS3, complexes of starch with other nonfermentable components as RS4, and starch–lipid complexes as RS5 were also present in DDGS. In general, the RS that escaped from the granular starch hydrolysis process was mainly RS1 and RS2, whereas that from the jet‐cooking process contained all types of RS (RS1 to RS5). Thus, the starch conversion efficiency and ethanol yield could be potentially affected by the presence of various RS in DDGS.     

Antimicrobial paper based on a soy protein isolate or modified starch coating including carvacrol and cinnamaldehyde

Soy protein isolates (SPI) and octenyl-succinate (OSA) modified starch were used as paper coating and inclusion matrices of two antimicrobial compounds: cinnamaldehyde and carvacrol. Antimicrobial compound losses from the coated papers were evaluated after the coating and drying process, and the two matrices demonstrated retention ability that depended on the compound nature and concentration. Whereas carvacrol losses ranged between 12 and 45%, cinnamaldehyde losses varied from 43 to 76%. The losses were always higher from OSA-starch-coated papers than from SPI-coated papers. During storage in accelerated conditions, at 30 degrees C and 60% relative humidity, carvacrol retention from coated papers was found to be similar whatever the coating matrices and the carvacrol rate. In contrast, the retention from SPI-coated papers was particularly high for the cinnamaldehyde concentration of 30% (w/w) compared to the lowest (10% w/w) or highest concentration (60% w/w). Compared to carvacrol, faster release was observed, particurlarly when OSA-starch was used. The antimicrobial properties of the coated papers were shown against Escherichia coli and Botrytis cinerea and explained by favorable conditions of total release of the antimicrobial agents.     

Effect of Partial Gelatinization and Lipid Addition on α‐Amylolysis of Barley Starch Granules

The effect of partial gelatinization with and without lipid addition on the granular structure and on α‐amylolysis of large barley starch granules was studied. The extent of hydrolysis was monitored by measuring the amount of soluble carbohydrates and the amount of total and free amylose and lipids in the insoluble residue. Similarly to the α‐amylolysis of native large barley starch granules, lipid‐complexed amylose (LAM) appeared to be more resistant than free amylose and amylopectin. Partial gelatinization changed the hydrolysis pattern of large barley starch granules; the pinholes typical of α‐amylase‐treated large barley starch granules could not be seen. Lipid addition during partial gelatinization decreased the formation of soluble carbohydrates during α‐amylolysis. Also free amylose remained in the granule residues and mostly amylopectin hydrolyzed into soluble carbohydrates. These findings indicate that lysophospholipid (LPL) complexation with amylose occurred either during pretreatment or after hydrolysis, and free amylose was now part of otherwise complexed molecules instead of being separate molecules. Partial gelatinization caused the granules to swell somewhat less during heating 2% starch‐water suspensions up to 90°C, and lipid addition prevented the swelling completely. α‐Amylolysis changed the microstructure of heated suspensions. No typical twisting of the granules was seen, although the extent of swelling appeared to be similar to the reference starch. The granules with added LPL were partly fragmented after hydrolysis.