Effect of low molecular weight dextrins on gelatinization and retrogradation of starch

!-Amylases, usually added to bread recipes as anti-firming agents, are known to produce low molecular weight dextrins by starch hydrolysis. The influence of these compounds on the gelatinization and retrogradation of starch was studied by differential scanning calorimetry. Adding oligosaccharides to starch caused a delay in gelatinization, although its extent was not quantified. However, oligosaccharides of degrees of polymerization (DP) 3-5 reduced the enthalpy of the retrogradation endotherm, shown as the staling endotherm. The addition of gluten to starch and starch/oligosaccharide mixtures had no effect on the gelatinization and retrogradation of starch. The retrogradation of starch in dough samples was also analysed, after 'baking' in the calorimeter, to obtain additional information about starch retrogradation during storage. Oligosaccharides of DP 3-5 also reduced the enthalpy of the retrogradation endotherm. This work provides evidence that oligosaccharides influence starch changes during the baking and storage of bread. These effects could be considered as the mechanism by which the bacterial !-amylase reduces starch retrogradation and acts as an anti-firming agent.     

Monitoring of Maillard reactions in soy products

Zusammenfassung Der chemische Mechanismus der Maillard-Reaktionen und die Literatur der für die Untersuchung der frühen Maillard-Reaktion vorgeschlagenen analytischen Methoden werden kritisch gesichtet. Wir belegen die Anwendbarkeit unseres Verfahrens für die Verfolgung der frühen Maillard-Reaktionen durch die Erfassung der daran Teilnehmenden, der löslichen Raffinose-Oligosaccharide und der basischen Aminogruppen der Proteine, und zwar am Beispiel der Analyse von unterschiedlich denaturierten Sojaprodukten. Hierbei ist es zum ersten Mal gelungen, die quantitativen Zusammenhänge zwischen den Maillard-Reaktanten in einer natürlichen Matrix mit numerischen Daten zu stützen, wobei mit dieser Methode keine Korrekturfaktoren benötigt werden.

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Monitoring of Maillard reactions in soy products

Summary Chemical mechanism and the analytical methods suggested in the literature for the analysis of early Maillard reactions are summarised and critically evaluated. The applicability of our method for the measurement of the Maillard reactions — the soluble raffinose oligosaccharides and the basic amino groups of proteins — are illustrated by following early Maillard reactions in differently denaturated soya bean samples. The quantitative relations of Maillard reactions taking place in natural matrices could be clarified by monitoring both of the reactants by means of methods not requiring correction factors.

     

Monitoring of Maillard reactions in soy products

Chemical mechanism and the analytical methods suggested in the literature for the analysis of early Maillard reactions are summarised and critically evaluated. The applicability of our method for the measurement of the Maillard reactions - the soluble raffinose oligosaccharides and the basic amino groups of proteins - are illustrated by following early Maillard reactions in differently denaturated soya bean samples. The quantitative relations of Maillard reactions taking place in natural matrices could be clarified by monitoring both of the reactants by means of methods not requiring correction factors.     

Volatiles from interactions of Maillard reactions and lipids.

This article provides current information on the production of volatile compounds from interactions of Maillard reactions and lipids. It includes a brief introduction outlining the Maillard reactions, the Strecker degradation of amino acids, and the oxidation of lipids. It highlights those compounds derived from these reactions that could interact to form volatile flavor components during the processing or cooking of food. The article discusses results obtained from model systems involving interactions between (1) Maillard reaction products and carbonyl compounds, (2) amino acids and carbonyl compounds, (3) amino acids and derivatives of fatty acids, and (4) Maillard reaction products, triglycerides and phospholipids. The qualitative and quantitative effects that triglycerides and phospholipids have on the formation of volatile Maillard products are also discussed. Particular attention is given to those long-chain alkyl heterocyclic compounds formed during these reactions, proposed methods for their formation, and their aromas. The role that such compounds play in food flavors is discussed with reference to those volatile compounds identified in certain cooked foods, such as meat (beef, lamb, and pork), chicken, potatoes (baked, French-fried, and crisps), and beverages (coffee, tea, and cocoa).     

Effect of heating on Maillard reactions in milk

Heated milk is subject to the Maillard reaction; lactose and lysine residues in milk proteins (mainly casein) are the reactants. An overview is given of the early, advanced and final stages of the Maillard reaction as it occurs in milk. The early Maillard reaction is confined to the formation of the protein-bound Amadori product lactulosyllysine. Breakdown of the Amadori product leads to formation of all kinds of advanced Maillard reaction products such as lysylpyrraline, pentosidine, hydroxymethylfurfural, (iso)maltol, furfurals and formic acid. The content of these compounds in heated milk is, however, very low (with the exception of formic acid), and does not correspond to the breakdown of Amadori product in quantitative terms. The final stage, in which melanoidins (brown pigments) are formed and protein polymerization occurs, is largely unknown from a chemical point of view, let alone quantitatively. The conclusion can only be that not all important compounds are yet identified. Some experimental data for heated milk are given to illustrate the various stages of the Maillard reaction in heated milk. A kinetic analysis of the Maillard reaction is difficult because it is such a complicated reaction with many parallel and consecutive steps; in addition, one of the reactants, lactose, is also subject to another reaction, namely isomerization followed by degradation. The kinetics can be tackled by kinetic, multiresponse modelling, and this approach is illustrated. It appears that the temperature dependence of the (early) Maillard reaction is lower than for the simultaneously occurring isomerization reactions of lactose. The use of several components formed in the Maillard reaction to evaluate the heat intensity given to milk is discussed.     

Browning reactions during storage of low-moisture Australian sultanas: Evidence for arginine-mediated Maillard reactions

Browning during storage of low‐moisture dried Vitis Vinifera L. cv. Sultana (Thompson Seedless) grapes was examined in a multifactorial treatment and storage trial. Grapevines were subjected to two different levels of sun exposure, harvested fruit was dipped and subjected to different drying treatments to obtain a range of initial moisture contents (a_w= 0.419–0.558). The storage effects of temperature (10^oC and 30^oC), and the presence of oxygen on colour change (CIE L*a*b* tristimulus values, hue‐angle (h_ab*)) and chroma (C_ab*) over a fourteen‐month period were observed. The most significant changes in colour were measured for samples stored at 30^oC, both aerobically and anaerobically, although the largest changes occurred in the presence of oxygen. Initial a_w had a strong effect on colour changes; higher a_w non‐sunfinished samples underwent more significant browning compared to lower a_w sunfinished controls regardless of their oxygen status. Changes in the concentration of the free‐arginine and free‐proline, the most abundant free amino acids in sultanas, were monitored throughout the storage period. Free arginine decreased significantly at 30^oC in both the absence and presence of oxygen, whereas free proline increased (at both 10^oC and 30^oC), implying that free proline did not play a role in browning reactions at those temperatures. In addition to the decreases in free arginine, the concentration of 5‐hydroxymethyl furfural (5‐HMF), a marker of Maillard browning reactions, increased significantly in samples stored at 30^oC. Significant differences in the concentrations of 5‐HMF under the two oxygen conditions indicated sultana Maillard reactions, and possibly other non‐enzymatic browning processes, were oxygen sensitive.     

Maillard reactions: do the properties of liquid matrices matter

The amounts of browning due to the interaction of lysine and xylose occurring when these reactants were in different liquids have been investigated. The reactants were suspended/solvated in water, corn oil, glycerol, different propylene gylcols and mixtures of these liquids. In water the amount of browning was found to equate to the concentration of the reactants to the third power. In glycerol and polypropylene glycol 76 ° the amount of browning was higher than that achieved for the same amount of reactants in water. In corn oil and polypropylene glycol 1200 no browning was observed. In all samples the addition of water to another liquid caused the level of browning to be increased, until a maximum was achieved. This maximum may have corresponded to the point where all the reactants were soluble in the matrix. Further addition of water decreased the amount of browning. In all cases the amount of browning seemed to relate to the concentration of the reactants if they were calculated as just occurring in the water portion of the matrix. Values calculated in this way were significantly, but constantly a little lower than the experimental results in all cases except for the corn oil, where the values directly corresponded. The predictability of these values was surprising considering that the matrices gave miscible and phase-separated systems.     

4种模式美拉德反应条件及其产物抗氧化作用

以精氨酸/赖氨酸-麦芽糖、壳聚糖-果糖/阿拉伯糖为模式制备美拉德反应产物,考察4种体系紫外可见光谱和荧光光谱随加热时间的变化,氨基与羰基物质的量比、初始pH、温度对产物褐变的影响及反应过程的pH值变化,探讨美拉德反应产物对DPPH·、HO·、H2O2的清除作用和总还原力。结果表明:4种体系紫外吸收峰均在260²80 nm,荧光激发波长在319280 nm,荧光激发波长在319³35 nm、发射波长约在420 nm和385 nm(壳聚糖-阿拉伯糖)。4种体系的褐变及精氨酸/赖氨酸-麦芽糖的酸度均随加热时间的延长而增加,壳聚糖-果糖/阿拉伯糖的酸度变化则无规律。当氨基与羰基物质的量比为1∶2335 nm、发射波长约在420 nm和385 nm(壳聚糖-阿拉伯糖)。4种体系的褐变及精氨酸/赖氨酸-麦芽糖的酸度均随加热时间的延长而增加,壳聚糖-果糖/阿拉伯糖的酸度变化则无规律。当氨基与羰基物质的量比为1∶2¹∶3,pH 111∶3,pH 11¹2和温度11012和温度110¹20℃时,各体系的褐变接近最大程度。精氨酸/赖氨酸-麦芽糖体系对DPPH·清除作用均随浓度增大而降低,对HO·清除作用均基本保持不变;对H2O2的清除作用和总还原力均表现出一定的量效关系。壳聚糖-果糖/阿拉伯糖体系对DPPH·的清除、HO·的清除及H2O2的清除作用均随浓度增大而增强,总还原力先增大后减小。     

Effect of Maillard reaction products prepared from glucose–glycine model systems on starch digestibility

The Maillard reaction is one of the most important phenomena occurring spontaneously during food processing and storage. However, research on the effects of Maillard reaction products (MRPs) on starch hydrolysis remains insufficient. To investigate the effects of MRPs on in vitro starch digestibility, the characteristics of glucose–glycine model system containing MRPs and digestive enzyme activities by MRPs were measured. MRPs were prepared by heating of glucose–glycine mixture solution at 90°C for different times (0, 1, 3, 9, 18, 24, and 48 h). As the Maillard reaction proceeded, browning intensity, and furosine and hydroxymethylfurfural content increased, whereas pH value decreased. The reducing power of MRPs was increased as the Maillard reaction progressed, and MRPs produced in 18 and 24 h showed the highest values (both 1.2). In MRPs heated for 48 h, the reducing sugar content and hydrolysis index were lowest values (88.6 and 87.0%) among the samples. The activity of digestive enzymes significantly decreased by adding of MRPs, as the browning of added MRPs increased. Therefore, MRPs seem to be contributed to decrease in starch digestibility, as shown by an enzymatic digestion result.     

Nonenzymic browning. XII. Maillard reactions in green coffee beans on storage.

During storage of green coffee beans at increased temperature and at constant humidity reducing sugars present in original beans react with free amino acids with formation of colourless unstable products. Additional reducing sugars and free amino acids are produced by hydrolysis of polysaccharides and proteins, respectively. The second stage of storage is characterized by only slight changes in the content of free amino acids and sugars but by intensive browning reactions. This latter stage was characterized by deterioration of sensory quality of coffee beverage, especially of its odour. Lysine combined in protein was involved in browning reactions via colourless intermediary products.     

糊化淀粉制备辛烯基琥珀酸淀粉酯的反应研究

对木薯淀粉进行糊化预处理,以辛烯基琥珀酸酐(OSA)为酯化剂,采用水相法制备辛烯基琥珀酸淀粉酯(OSAS),并通过与颗粒木薯淀粉比较,研究水相法制备OSAS的反应条件和传质过程对酯化选择性的影响。实验结果表明:反应温度升高可提高酯化选择性,p H升高酯化选择性先增大后降低、在p H 9.0有最大值,较低范围的淀粉用量增大时利于提高酯化选择性、但过高的淀粉用量则会降低酯化选择性,过长的反应时间会降低酯化选择性,而OSA用量对选择性则无影响。糊化淀粉和颗粒淀粉比较结果发现,前者酯化选择性高达88%以上,约为后者的3倍,说明淀粉糊化后可显著降低或消除颗粒淀粉存在的传质阻力,从而可提高酯化选择性。     

Yellow dextrins: Evaluating changes in structure and colour during processing

The preparation of a yellow dextrin is thoroughly characterized during different stages of its production process with a SEC system equipped with four detectors (light scattering, viscosity, UV and RI). With this system, also referred to as SEC‐4D, it was shown that the changes in characteristics are only in line with initial expectations up to 5 h after initiation of the reaction. After 5 h, changes in molar mass, intrinsic viscosity and colour point to the presence of significantly different structures. The combined results of the SEC‐4D measurements indicate the formation of aggregate like structures made of small starch fragments which are intensely coloured and physically linked. The obtained results also indicate that the aggregate like structures are probably still susceptible to repolymerization and transglycosylation. The newly derived parameter YI‐400 nm played an important role in defining a plausible cause for the observed changes in characteristics.     

乙偶姻与美拉德反应

阐述乙偶姻（3-羟基丁酮）的化学性质及其生成途径;美拉德反应的实质是羰氨褐变反应。乙偶姻是枯草芽孢杆菌发酵产物,也是美拉德反应的前驱物质。但它存在并不代表四甲基吡嗪来源于大曲中的枯草芽孢杆菌。     

Hydrolysis of starches and flours by sorghum malt amylases for dextrins production

Corn and wheat starches as well as wheat and cassava flours were hydrolyzed using sorghum malt at 65 °C for 6 h. During these reactions, dextrose equivalent (DE) values were followed under three concentrations of sorghum malt and calcium chloride. Wheat flour presented the highest DE values and cassava flour had the highest hydrolysis yield. Thus, different dextrins were produced in a pilot plant and were analyzed by HPSEC and HPAEC-PAD for their molecular weight distribution and oligosaccharides composition, respectively. The results indicated that oligosaccharides with broad molecular weight distributions were present in the dextrins produced and that the proportion of maltose was very high.     

Browning reactions during storage of low-moisture Australian sultanas: Further evidence for arginine-mediated Maillard reactions during storage, and some effects of vine-shading and harvest date

Sultana grapevines (Vitis Vinifera L. cv. Sultana syn. Thompson Seedless) were subjected to four shading regimes: 50% shading (1), 25% shading (2), fully exposed‐top of canopy (3) and beneath canopy (4) and harvested early (21 February) and late (13 March) in the 1996/1997 sultana season. Grapes from each of the eight field‐treatment combinations represented a range of maturities (14.4 to 23.50^oBrix). Grape samples from each of the treatments were dipped and dried to 18% moisture, with half of each of the sultana samples further reduced in moisture by sunfinishing on plastic sheets in direct sun. These field treatments resulted in sixteen unique dried sultana bulk samples with a range of initial chemico‐physical properties; a_w (0.481–0.691), skin‐polyphenoloxidase (PPO) activity (4.40–9.05 μmol O₂/g.minute) free arginine in skin tissues (1.0–5.10 mg/g) and protein (16.40–27.18 mg/g). Sultanas were stored at 10^oC and 30^oC in either the presence or absence of oxygen for 10 months, and changes in CIE L*a*b* tristimulus values, hue‐angle (h_ab*) and chroma (C_ab*) were monitored. Significant changes in sultana colour occurred in samples stored at 30^oC, especially in higher a_w non‐sunfinished sultanas. Although browning was more intense in the presence of oxygen, significant browning also occurred in the absence of oxygen. Lower concentrations of 5‐hydroxy methylfurfural, a key marker of Maillard browning in samples stored at 30^oC in the presence of oxygen, indicated that the non‐enzymatic reactions were sensitive to oxygen. Changes in the concentration of trans‐caftaric acid, the main substrate of grape PPO, were also measured during sultana drying. Storage browning (changes in L*, b*, h_ab*, C_ab*)in dried sultanas could be predicted by regression models using pre‐storage a_w, free‐skin arginine or Kjeldahl protein after 10 months' storage between 10^oC and 30^oC. Non‐enzymatic and Maillard‐type reactions (sensitive to both oxygen and a_w), made an important contribution to sultana storage browning. We provide only weak evidence that either shaded (immature) or green fruit was more susceptible to storage browning.     

ning reactions during storage of low-moisture Australian sultanas: Effects of vine nitrogen nutrition on subsequent arginine-mediated Maillard reactions during storage of dried fruit

Ten‐year old Vitis Vinifera L. cv. Sultana (Thompson Seedless) grape vines were transferred into large cement pots in low nitrate soil and supplemented with four levels of nitrogen application in the form of ammonium nitrate as follows: 0 g ( N₀ ), 8.5 g ( N₁ ), 17.0 g ( N₂ ) and 25.0 g ( N₃ ). Grapes were harvested from each nitrogen treatment, dipped and dried to low moisture (?11.4%) and subsequently stored for 10 months at 10^oC and at 30^oC in either the presence or absence of oxygen. The pre‐storage concentration of free arginine, free‐proline and total protein in the dried sultanas increased with soil nitrogen application. Skin‐polyphenoloxidase (PPO) activity was higher in sultanas with added soil nitrogen ( N₁, N₂, N₃ ), however pre‐storage differences in total phenolics, and the PPO substrate, trans‐caftaric acid, were not significantly different. After 10 months storage at 30^oC significant browning was observed in both the presence and absence of oxygen. Greater browning corresponded to higher soil‐nitrogen application rates. The concentration of skin trans‐caftaric acid did not decrease in N₀, N₁ or N₂ after 10 months at 30^oC, in either the presence or absence of oxygen, although some decreases were measured in the highest nitrogen sultanas ( N₃ ). While PPO oxidation of the phenolic substrate trans‐caftaric acid was not the primary route to browning, a number of Maillard reaction products (MRP) were present in both sultanas and arginine‐glucose model systems. Those products were separated via reverse phase HPLC and partially characterised by UV‐diode array spectroscopy. The lack of oxidation of trans‐caftaric acid observed in the nitrogen storage trial was confirmed in an accelerated browning experiment in low‐moisture sultanas, where despite browning at 50^oC after 12 days, no decreases in this primary substrate for PPO‐mediated oxidation were measured.