Gelatinisation Characteristics of Cassava Starch Settled in the Presence of Different Chemicals

Addition of chemicals during the extraction of cassava starch for enhancing the settling rate, whiteness and compactness of the settled starch is an accepted commercial practice. The effect of addition of selected chemicals such as acids (sulphuric and hydrochloric acids), bleaching and oxidising agents (sodium metabisulphite and sodium hypochlorite) and alum during settling on the thermal and pasting properties of the cassava starch was examined. Treatment with sulphuric acid produced a noticeable increase in all DSC gelatinisation parameters, viz. onset gelatinisation temperature (T_o), temperature at peak minimum (T_p) and end temperature (T_e), with increasing concentration of acid, while only a marginal shift could be obtained even at higher concentration of hydrochloric acid. However, no major effect resulted from treatment with sodium metabisulphite, sodium hypochlorite and alum. The gelatinisation enthalpy was hardly affected by the treatments. An exception was hydrochloric acid, which brought about a perceptible decrease in enthalpy at higher concentrations indicating that starch crystallinity is influenced to a small extent by hydrochloric acid. Pasting characteristics studied using a Rapid Visco Analyser showed that sulphuric acid, even at the lowest concentration (5 mM), considerably affected the structural characteristics of cassava starch, while hydrochloric acid induced similar effect only at higher concentrations. Alum reduced the paste viscosity while the bleaching agents (sodium metabisulphite and sodium hypochlorite) were not so effective in modifying the starch viscosity characteristics.     

Effects of the Barley amo1 and wax Genes on Starch Structure and Physicochemical Properties

Starch structural mutants showing abnormal endosperm characteristics have been used for investigating the effects of the mutation on structure and physicochemical properties of starches. Inbred lines of barley cultivars ‘Shikoku Hadaka 97’ and ‘Glacier AC38’ were used to investigate the impact of amo1 and waxy genes on starch properties. The amo1 type starch had high apparent amylose content and low starch content. The amo1+waxy type starch contained very little amylose. The content of long chains of amylopectin as detected with high‐performance size‐exclusion chromatography (HPSEC) was decreased, and that of amylopectin chains with the degree of polymerization (DP) of 12‐36 was increased in amo1 and amo1+waxy type starches. The amo1 and amo1+waxy type starches exhibited high gelatinization temperatures and low gelatinization enthalpies.     

高直链玉米淀粉添加对挤压荞麦面条结构、蒸煮品质及消化特性的影响

制备挤压荞麦面条,研究不同添加量（10%、20%、25%、30%）的高直链玉米淀粉（m/m,基于全粉）对挤压荞麦面条结构、蒸煮品质及消化特性的影响。结果表明,随着高直链玉米淀粉添加量的增加,挤压面条直径减小,糊化度降低。X射线衍射结果表明添加高直链玉米淀粉后,面条除了V型结晶峰外还存在未完全糊化的直链淀粉的典型B型峰。热力学性质结果也表明直链淀粉发生部分糊化。添加高直链玉米淀粉后,面条色泽变浅变亮,最佳蒸煮时间缩短,蒸煮损失率由9.90%增加到12.43%。当高直链玉米淀粉添加量为25%时,面条开始出现断条。面条硬度由2 105.709 g显著增加至3 680.401 g,弹性由0.961降低至0.866。扫描电镜结果表明,随着高直链玉米淀粉添加量的增加,致密的面条结构逐渐出现裂纹,且面条截面有较多未完全糊化的淀粉颗粒。淀粉体外消化实验表明,随着高直链玉米淀粉添加量的增加,淀粉水解率逐渐下降,预计血糖指数减小,抗性淀粉含量增加。当高直链玉米淀粉添加量为30%时,挤压荞麦面条的预计血糖指数从74.28降至66.31,抗性淀粉含量从34.43%增加至47.86%。     

Characteristics of Different Types of Starch in Starch Noodles and Their Effect on Eating Quality

Several commercial starch noodles made from legume, tuber, geshu (kudzu and sweet potato) and fernery starches were used to study the characteristics of starch in starch noodles and their effect on eating quality of starch noodles. Scanning electron microscopy observation found that the special inner structure of starch noodles was composed of some broken starch granules and some gel-like substances. Tuber and legume starches had the highest and lowest solubility, swelling power, swelling factor, setback, breakdown, peak viscosity, and final viscosity, respectively. Legume and tuber starches had the highest and lowest gelatinization temperature, respectively. Tuber and geshu starches had the highest amylose leaching rate, while legume starches owned the lowest value (p < 0.05). Tuber starches had the highest conclusion temperature of gelatinization (151.12~158.86°C). Fernery starches had the lowest value of retrogradation enthalpy (967.33 J/g dry starch). Legume starch noodles had the lowest broken rate (0.00~1.67%), swelling ratio (332.64~343.57%), and cooking loss (2.40~2.74%), and the highest hardness (87.47~93.29 g/mm2), shear deformation (0.49~0.52), and elasticity (0.58~0.62), However, tuber and fernery starch noodles did the opposite, tuber and legume starch noodles had the highest and lowest cohesiveness, respectively. All the above cooking and starch properties test results of starch noodles demonstrated that, compared with others, legume starch noodles are relatively well in eating quality. The correlation analysis showed that the cooking and physical quality of starch noodles could be perfected significantly by improving the swelling and pasting properties for starch of starch noodles, while thermal properties had no obvious influence on them.     

The (1–3, 1–4)‐β‐Glucanases in Malting Barley: Enzyme Survival and Genetic and Environmental Effects

Eighteen barley genotypes used in Brazilian malting barley breeding programs were characterized in relation to (1–3, 1–4)‐β‐glucanase activity in green and kilned malt. They were tested to determine the loss of enzyme activity during kilning in the malting process and the environmental effects on enzyme activity were measured. The genotypes analyzed showed great variation regarding the enzyme activity in both kinds of malt, in a range from 531.94 to 934.31 U/kg in green malt, and from 187.02 to 518.40 U/kg in dry malt. The mean enzyme activity loss during kilning was close to 60%, very similar to the results obtained in other studies. The loss among genotypes varied from 8.04% to 71.54%. The enzyme activity varied significantly under the different environments tested, showing existence of environmental effects on the genotypes analyzed. Embrapa 127 was the genotype that exhibited the highest enzyme activity in finished malt although it had shown a low activity in green malt, reflecting a negligible loss of activity during kilning. The data indicate promising results to malting barley breeding due to the wide variability exhibited by genotypes as to enzyme activity and levels of isoenzyme with high thermostability.     

Comparison of the GFFF and LALLS Methods for the Measurement of Starch Granule Size Distribution in Spring Barley Caryopses

A newly developed method GFFF (Gravitational Field‐Flow Fractionation) and the well known method LALLS (Low Angle Laser Light Scattering) were used to assess starch granule size distribution of ten varieties of spring barley. As a distribution criterion, the ratio of starch granule content larger than 8 μm (type A) and smaller than 8 μm (type B) was chosen. Both methods divided the observed set in a similar way. Varieties Akcent, Forum and Atribut formed a variety set with the highest ratio of large and small starch granules. Varieties Scarlet and Kompakt had intermediate ratios. The remaining five varieties Amulet, Novum, Olbram, Tolar and Krona had the lowest ratios of large and small starch granules. Statistical analysis showed that there was a highly significant correlation between the GFFF and LALLS methods.     

不同类型抗性淀粉的多尺度结构特征与肠道菌群调节功能研究进展

抗性淀粉具有改善肠道菌群结构、调节糖脂代谢及维护机体健康等方面的作用,近年来国内外学者对此进行了广泛的研究。不同类型的抗性淀粉能够对肠道菌群产生特定的影响,从而表现出不同的生理功能。本文介绍了不同类型抗性淀粉的表观形貌结构与多尺度结构特征,比较了不同类型抗性淀粉对肠道菌群、短链脂肪酸生成情况、肠道健康以及糖脂代谢的影响,对抗性淀粉类型与肠道菌群调节功能之间的潜在关联进行了较全面的综述,为个性化设计抗性淀粉和精准调控肠道菌群提供参考。     

不同熟化方式对青稞淀粉体外消化及多酚利用特性的影响

以青稞粉为研究对象,结合体外模拟消化,探究挤压和煮制对青稞淀粉体外消化和多酚含量及抗氧化活性的影响。结果表明：不同处理显著提高了青稞粉的水解率,其中青稞挤压粉的水解率和预估血糖生成指数最高,抗性淀粉含量最低。不同处理均显著降低了未消化青稞粉中总酚、总黄酮含量和抗氧化活性,其中煮制处理分别降低了32.8%、30.5%、26.7%（FRAP法）和14.8%（TEAC法）。与模拟胃消化相比,模拟肠消化阶段显著提高了青稞粉总酚、总黄酮的释放量及其生物有效性,并主要集中在模拟肠消化的前30min;与未消化样品相比,模拟胃肠消化后,青稞粉自由基清除能力提高4倍左右。此外,消化后结果同样表明,煮制处理对青稞酚类物质和抗氧化活性的生物有效性破坏较大。     

Effect of raw and heat–moisture‐treated high‐amylose corn starches on the process of digestion in the rat digestive tract

High‐amylose corn starch (HAS) is widely known as a resistant starch foodstuff. We developed heat–moisture‐treated high‐amylose corn starch (HMT‐HAS) that was more resistant to enzymatic hydrolysis. Resistant starch contents of HAS and HMT‐HAS using the enzymatic–gravimetric method were found to be 30% and 65% respectively. Rats were given 10% ordinary corn starch (CS), HAS or HMT‐HAS by meal feeding for 10 days. The caecum contents increased and the caecal pH was lower after their diets were supplemented with HAS and HMT‐HAS. Starch contents increased in the upper and the lower small intestine with HAS and HMT‐HAS. Caecal starch with HAS and HMT‐HAS was more than that with CS. Particularly, caecal starch with HMT‐HAS was seven times more than that with HAS. There were no differences in starch content in the large bowel between CS and HAS, but the content increased with HMT‐HAS. These results suggested that HAS and HMT‐HAS were resistant to digestion and absorption in the small intestine, and any indigestible starches reached the caecum. In the caecum, HAS was hydrolysed almost completely by intestinal bacteria; however, some HMT‐HAS escaped bacterial hydrolysis. This escaped HMT‐HAS reached the large bowel and was excreted in the faeces. © 1999 Society of Chemical Industry     

The Advantages of Using Natural Substrate‐Based Methods in Assessing the Roles and Synergistic and Competitive Interactions of Barley Malt Starch‐Degrading Enzymes

Existing methods of assay of malt starch‐degrading enzymes were critically appraised. New methods based on natural substrates, namely starch and its natural intermediate‐derivative, were developed for all the enzymes, except limit dextrinase for which pullulan was used. Thermostability, optimal temperatures and pHs were established. α‐Amylase and limit dextrinase were the most thermostable and β‐amylase, α‐glucosidase and maltase were the least stable while diastase occupied an intermediate position. The optimal temperatures were congruent with thermostability, β‐ amylase having the lowest (50°C) and α‐amylase the highest (65°C) with the remaining enzymes, including diastase, falling in between. In contrast, α‐amylase has the lowest optimal pH (pH 4.5) and β amylase the highest (pH 5.5) while the others have pHs in between the two values. The roles of the enzymes were evaluated taking into account the level of activity, thermostability, optimum pH, the nature of the product(s), and the relevance to brewing. β‐Amylase production of maltose was synergistically enhanced, mostly by α‐amylase but also limit dextrinase. α‐Glucosidase and maltase are unimportant for brewing, because of their low activity and the negative impact on β‐amylase activity and the negative effect of glucose on maltose uptake by yeast. The starch‐degrading enzymes (diastase) in a gram of malt were able to degrade more than 8 g boiled starch into reducing sugars in 10 min at 65°C. The latter, suggests that it will be possible to gelatinise most of the malt starch at a higher temperature and ensure its hydrolysis to fermentable sugars by mixing with smaller portions of malt and mashing at lower temperatures e.g. 50–60°C.     

Mathematical modelling of the heat inactivation of trypsin inhibitors in soymilk at 121–154 °C

Response surface methodology (RSM) was used to investigate the effects of processing temperature and time on the inactivation of trypsin inhibitors (TI) in soymilk. The factorial experimental design consisted of four levels of temperature and six levels of time in a temperature range of 121–154 °C and a time interval of 10–90 s. A quadratic polynomial equation, relating log(% TI retained) as a function of heating time and temperature, was satisfactorily fitted to the experimental data by least squares regression with r² (correlationcoefficient) = 0.959. Within the range of heating times investigated, TI in soymilk was satisfactorily destroyed to 10% retained at 143 and 154 °C with 62 and 29 s heating time respectively. © 2002 Society of Chemical Industry     

Proteolytic Clostridium botulinum growth at 12–48°C simulating the cooling of cooked meat: development of a predictive model

The objective of this study was to develop a model to predict the germination, outgrowth and lag (GOL), and exponential growth rates of Clostridium botulinum from spores at temperatures (12–48°C) applicable to the cooling of cooked meat products. The growth medium, Reinforced Clostridial medium (RCM) supplemented with oxyrase enzyme to create suitable anaerobic conditions, was inoculated with approximately 4 log₁₀spores ml⁻¹. Clostridium botulinum populations were determined at appropriate intervals by plating onto RCM. Clostridium botulinum growth from spores was not observed at temperatures <12°C or >48°C for up to 3 weeks. Growth curves were determined by fitting Gompertz functions to the data. From the parameters of the Gompertz function the growth characteristics, GOL times and exponential growth rates were calculated. These growth characteristics were subsequently described by Ratkowsky functions using temperature as the independent variable. Closed form equations were developed that allow for predicting relative growth for a general cooling scenario. By applying multivariate statistical procedures, the standard errors and confidence intervals were computed on the predictions of the amount of relative growth for a cooling scenario. The predictive model is capable of predicting spore outgrowth and multiplication for general cooling scenarios, for suitable but un-verified mathematical assumptions, and should aid in evaluating the safety of cooked products after cooling.     

The effect of long‐term alkali treatment on the molecular characteristics of native and extruded starches at 35°C

In this study the molecular characteristics of native and extruded starches of wheat, corn, and potato were observed under long‐term alkali treatment (0.5 M NaOH, 7 days, 35°C). The molar mass distribution of samples determined by means of calibrated semi‐analytical size exclusion chromatography (SEC) showed different profiles (double and single peak distribution) depending on the dissolution status of the starch polysaccharides with simultaneous loss of supermolecular structures because of disintegration of the aggregates. The molecular range was between 4 × 103 and 2 × 106 g/mol and their calculated average molar masses were M_w = 1.7 × 105–4.1 × 105 and M_n = 2.5 × 104–1.1 × 105 g/mol. The reduction value and the value of intrinsic viscosity were additional indicators for the dissolving status of starch polysaccharides as well as for the stability of starch molecules in alkaline solution.     

Shelf life of shrimp (Penaeus merguiensis) stored in ice (0°C) and partially frozen (—3°C)

Sensory, biochemical and microbiological changes and changes in SDS-PA GE patterns of myofibrillar and sarcoplasmic proteins were studied in shrimp (Penaeus merguiensis) muscle during storage at partial freezing temperature (—3°C; PFS) and in ice (0°C; IS). During PFS up to 20 days there were slight changes in biochemical parameters, apparently no changes in microbiological populations, and no changes in electrophoretic protein patterns. Rapid changes in these parameters occurred in IS over the same period. Sensory assessment of shrimps stored at PFS showed that a considerable increase in prime quality life was possible at this temperature over shrimps in IS. Prime quality life of shrimps in PFS was found to be 16 days, compared with 8 days in IS. Extension of prime quality life was attributed to the significantly slower rate of biochemical and microbiological changes at PFS compared with IS. Changes in sensory properties were associated with changes in some of the chemical properties.     

Dormancy in Malting Barley: Quantifying the Effect of Storage Temperature on Different Varieties and the Response to Sudden Cooling

The rates of break of dormancy of the varieties Blenheim and Pipkin were examined during storage at temperatures of 8, 18, 26 and 33°C. The results were fitted to an established probit model of dormancy and compared with the previously fitted equations for Triumph. Triumph was shown to be the variety with the slowest recovery rate and this was consistent with the observations of other researchers. A similarity between varieties in the change of recovery rate with temperature suggested a consistency in the controlling reaction. A second experiment examined whether the sudden cooling of warm barley could induce ‘secondary dormancy’. The variety Triumph was stored at 12% moisture content and 33°C. Samples were then transferred to 8 or 15°C at different times. This procedure did not bring about any significant reduction in germinative energy. The only effect of a sudden temperature drop was a reduction in the rate of emergence from dormancy. ‘Secondary dormancy’ was not induced. The work is introduced and the results discussed in the context of the development of a thermally based integrated control strategy for malting barley. The strategy was designed to minimise the use of chemicals.     

Moisture adsorption isotherms of Tarhana at 25 °C and 35 °C and the investigation of fitness of various isotherm equations to moisture sorption data of Tarhana

Moisture adsorption isotherms of Tarhana were determined at 25 °C and 35 °C. As the temperature increased, the adsorbed moisture content decreased at water activities between 0.2 and 0.9. The experimental sorption data obtained were applied to the Halsey, Harkins‐Jura, Smith, BET and Freundlich isotherm equations to test fitness of these equations to Tarhana. The order of best fit or sorption data obtained for Tarhana was Halsey > Harkins‐Jura > Smith > Henderson > BET > Freundlich. The obtained sorption data fitted the Halsey, Harkins‐Jura and Smith isotherm equations quite well in the 0.2–0.9 water activity range; However, the best fit was obtained in the Freundlich, BET and Henderson isotherm equations in this water activity range. © 2000 Society of Chemical Industry     

Original article: The effect of freezing at −18 °C and −70 °C with and without ascorbic acid on the stability of antioxidant in extracts of apple and orange fruits

The influence of low temperature and storage time on the antioxidant capacity of standard solutions and apple and orange extracts was evaluated. In addition, the effects of ascorbic acid (AA) addition to the fruit extracts in terms of antioxidant capacity, AA content and soluble and hydrolyzable polyphenol contents were also analysed. Polyphenol contents in both apple and orange extracts were stable during storage period, which reflected also in the antioxidant capacity stability. Freezing at ?18 °C did not result in different retention rates for polyphenols, AA and antioxidant capacity when compared to freezing at ?70 °C. However, vitamin C content in orange juice, without AA addition, slightly increased along the experimental period (10 days). Thus, this study shows that it may not be necessary to measure the antioxidant capacity immediately after the preparation of fruit extracts or antioxidant standard solutions.     

Growth of Bacillus cereus in natural and acidified carrot substrates over the temperature range 5–30°C

Minimally processed refrigerated foods have a relevant potential in the food market, although the potential risk posed by sporulated emerging psycrotrophs pathogens has to be evaluated. Bacillus cereus is one of these pathogenic micro-organisms. In this paper, the ability to grow of several strains of B. cereus in nutrient broth and in a carrot-based substrate (broth) was evaluated. All the strains tested grew at 12°C or higher temperatures both in nutrient broth and in carrot substrate. One of the strains was able to grow rapidly even at 5°C. Acidification of the carrot substrate proved to be efficient inhibiting B. cereus. For the two strains tested, growth was not observed at pH below 4·75 acidifiying with citric acid or with lemon juice. When the effect of pH was combined with refrigeration, acidification at pH 5·0 was sufficient to inhibit B. cereus at 12°C or lower temperatures. Therefore, the combination of these two factors could have a great potential to control B. cereus growth in minimally processed foods, such as carrot based products. Additionally, lemon juice can be considered as a more natural alternative to citric acid.