玉米高压糊化淀粉的老化特性和变色性质

研究了玉米淀粉高压糊化后的冻融稳定性和色泽变化，并和热糊化淀粉的老化特性和色泽变化做了比较。高压完全糊化淀粉糊没有与热加工糊化淀粉糊相同的老化现象。同时，高压不象热加工使玉米淀粉的颜色变黄。     

NIR‐FT/Raman Spectroscopy for Nutritional Classification of Cereal Foods

The classification of cereals using near‐infrared Fourier transform Raman (NIR‐FT/Raman) spectroscopy was accomplished. Cereal‐based food samples (n = 120) were utilized in the study. Ground samples were scanned in low‐iron NMR tubes with a 1064 nm (NIR) excitation laser using 500 mW of power. Raman scatter was collected using a Ge (LN₂) detector over the Raman shift range of 202.45~3399.89 cm^‐1. Samples were classified based on their primary nutritional components (total dietary fiber [TDF], fat, protein, and sugar) using principle component analysis (PCA) to extract the main information. Samples were classified according to high and low content of each component using the spectral variables. Both soft independent modeling of class analogy (SIMCA) and partial least squares (PLS) regression based classification were investigated to determine which technique was the most appropriate. PCA results suggested that the classification of a target component is subject to interference by other components in cereal. The Raman shifts that were most responsible for classification of each component were 1600~1630 cm^‐1 for TDF, 1440 and 2853 cm^‐1 for fat, 2910 and 1660 cm^‐1 for protein, and 401 and 848 cm^‐1 for sugar. The use of the selected spectral region (frequency region) for each component produced better results than the use of the entire region in both SIMCA and PLS‐based classifications. PLS‐based classification performed better than SIMCA for all four components, resulting in correct classification of samples 85~95% of the time. NIR‐FT/Raman spectroscopy represents a rapid and reliable method by which to classify cereal foods based on their nutritional components.     

Method for Determining the Rate and Extent of Accelerated Starch Retrogradation

A method to accelerate and quantitate retrogradation of starch pastes using a freeze-thaw cycle (FTC) process and turbidometric analysis has been developed. Using this method and differential scanning calorimetry (DSC), it was determined that the rate of retrogradation in 2.5% waxy maize pastes was inversely correlated to the rate of freezing, and that the thawing temperature affected perfection of the crystallites in retrograded amylopectin. DSC and X-ray diffraction were used to determine whether the crystallites formed during the FTC process were the same as those formed in starch pastes held isothermally at 4°C. Analysis of retrogradation of pastes of starches from various botanical sources indicated that the method reflects retrogradation in higher concentration pastes. Retrogradation rates were reduced by the addition of sodium dodecyl sulfate. Microstructures of freeze-thaw processed waxy maize and common corn starch pastes were examined.     

Understanding the Physicochemical and Functional Properties of Wheat Starch in Various Foods

This report highlights the structure and myriad properties of wheat starch in various food systems. Granule shape, size, and color, plus the proportion of A‐ and B‐granules, amylose content, and molecular structure largely determine its functionality in food. The role of wheat starch is portrayed in three categories of flour‐based foods that differ in water content. Wheat starch influences the appearance, cooking characteristics, eating quality, and texture of pasta and noodles, and its role is more than a filler in yeast‐leavened bread products. Recent developments in the properties and applications of commercially important wheat pyrodextrins and RS4‐type resistant wheat starches are reported, along with their use to produce fiber‐fortified foods. Gluten‐free foods are also discussed.     

抗性淀粉在食品中的应用及功效研究进展

淀粉是人类从饮食中获取能量的主要来源,对维持人体正常生命活动有着重要意义。抗性淀粉是指在小肠中不能被消化吸收,但2h后可到达结肠并被结肠中的微生物菌群发酵,继而发挥有益的生理作用的淀粉。因此,抗性淀粉被看作是膳食纤维的组成成分之一。长期以来研究学者将抗性淀粉分为4种,即RS1-4,现在认为还存在第5种类型,即RS5。当淀粉与脂类之间发生相互作用时,直链淀粉和支链淀粉的长链部分与脂肪醇或脂肪酸结合形成的复合物称为RS5。抗性淀粉已广泛地应用在面条、面包及油炸食品中。抗性淀粉具有预防结肠癌、降低血液胆固醇含量、减少肥胖和结石的发病率、增加矿物质吸收、控制糖尿病等生理功能。本文主要对抗性淀粉的5种类型、抗性淀粉在食品中的应用以及对人体健康的影响进行综述,旨在为富含抗性淀粉产品的开发及其对人体健康状况的改善提供理论依据。     

Development of a Novel Staining Procedure for Visualizing the Gluten–Starch Matrix in Bread Dough and Cereal Products

A novel staining procedure has been developed to visualize the gluten– starch matrix in wheat flour dough. Dough samples mixed to the final stage were stained with 26 fluorescent reagents, and each stained sample was observed with three sets of fluorescence filters (blue, green, and red). Of all the combinations of reagents and filters, the combination of acid magenta and the blue fluorescent filter set was the most effective in distinguishing starch granules from gluten network structure. Its effectiveness was further demonstrated with gluten and starch granule samples, in which the contrast was clearer when observed with the blue fluorescent filter set than without any fluorescent filter. Visualizing the gluten–starch matrix in dough samples at four mixing stages with the same procedure resulted in clear identification of the changes in gluten network structure because of the differences in mixing stages. The same procedure also enabled us to distinguish starch from gluten in white salted noodles, baked cookies, and flour particles. The proposed procedure is quicker, simpler, and has a lower risk of altering the sample than other conventional ones, and it is expected to become a useful tool in cereal studies.     

Determination of Damaged Starch and Diastatic Activity in Wheat Flour Using a Flow-Injection Analysis Biosensor Method

The determination of damaged starch and diastatic activity in flour was studied using a flow-injection analysis (FIA) biosensor system. The system consisted of an oxygen electrode and an immobilized enzyme column containing purified glucoamylase and glucose oxidase immobilized on activated aminopropyl glass beads. The biosensor system has an optimum pH between 6.5 and 7.5 and an optimum temperature of 35°C for glucose measurement. The response of the FIA biosensor was linear up to 1.000 g/L of glucose with a lower detection limit of 0.025 g/L. Each assay took about 20 min, and the system showed good reproducibility (r = 0.998, n = 8). When applied to the measurement of damaged starch and diastatic activity in wheat flour, the results obtained agreed with those obtained using the conventional methods of measurement. This biosensor system is a rapid practical alternative for the measurement of damaged starch and diastatic activity in wheat flour.     

A Program for Determining Cocompost Blending Ratios

? A program is presented that computes blending ratios for two ingredients of a co-compost. The program is written in the RPN language, requires 61 lines of memory, and will support hand-held programmable calculators, making it suitable for use in the field. Use of this program allows the composter to determine blending ratios quickly and with increased precision and accuracy.     

Determining the Role of Starch in Flour Tortilla Staling Using α‐Amylase

Effects of α‐amylase modification on dough and tortilla properties were determined to establish the role of starch in tortilla staling and elucidate the antistaling mechanism of this enzyme. Control and amylase‐treated tortillas were prepared using a standard bake test procedure, stored at 22°C, and evaluated over four weeks. Amylase improved shelf‐stability of tortillas. The enzyme also produced a significant amount of dextrins and sugars, decreased loss of amylose solubility, and weakened starch granules. Amylopectin crystallinity increased with time, but was similar for the control and treated tortillas. Staling of tortillas appears to mainly involve the starch in the amorphous phase. As such, amylase activity does not significantly interfere with amylopectin crystallization. It is proposed that amylase partially hydrolyzed the dispersed starch (i.e., mostly amylose), starch bridging the crystalline region, and protruding amylopectin branches. Starch hydrolysis decreases the rigid structure and plasticized polymers during storage. The flexibility of tortillas results from the combined functionalities of the amylose gel and amylopectin solidifying the starch granules during storage. Protein functionality may also be involved in tortilla staling, but this needs further research.     

A Method for Determining Phosphate Diffusion Coefficients by Bulk Diffusion in Soil

A method is described for the determination of phosphate diffusion coefficients by bulk diffusion in soil using the concentration distance method. Two soil blocks only differing in phosphate concentration are brought into contact. After a diffusion period of two weeks the soil blocks are separated, frozen in liquid nitrogen and sliced into layers about 0.02 cm thick by means of a refrigerated microtome. The soil samples are extracted with 4 N HCl, a procedure which fully recovers the added amount of fertilizer P and thus includes the total amount of P that diffuses from one soil block to the other. A concentration distance profile for P and a calculation of the P diffusion coefficient is presented.     

A Rapid General Method for Appraising the Rheological Properties of the Starchy Endosperm of Cereal Grains

A rapid, simple method was developed to prepare small, parallelepipedal test samples of endosperm of wheat, corn, and rice grains. Compression tests performed on endosperm samples revealed the following mechanical properties: modulus of elasticity (E, GPa), breaking stress (σ_rup, MPa), and maximum breaking strain (∊_rup, %). All tests were performed on several endosperm test samples of each cereal species. The results displayed good repeatability and several significant differences in the mechanical behavior of different endosperm structures, especially among soft, hard, and durum wheats. Rice and corn endosperm displayed mechanical behavior similar to that of durum wheat endosperm. The method proposed appears to be sufficiently sensitive and repeatable for studying the incidence of hardness and vitreousness of cereal grain endosperm in relation to its suitability for milling.     

Methods for Determining Relative Average Number of Channels per Maize Starch Granule and Digestion of Raw Granules of Mutant Maize Cultivars by Amyloglucosidase

Six methods were investigated for determining the relative average numbers of channels per granule in populations of starch granules. The first method involved digestion of raw starch granules with amyloglucosidase. There were differences in the rates of digestion of starch of the same mutation in two different inbred‐line backgrounds, but we concluded that a better method was needed. Three methods involved measuring either all channel proteins or one specific protein. Extraction of granules using 70% 2‐propanol containing 1% 2‐mercaptoethanol (ME) was successful in removing the majority of external surface proteins (<31 kDa). Further extraction of starch granules using 0.1% SDS containing 0.2% ME, pH 8, removed channel proteins without extracting matrix proteins. By measuring SDS‐PAGE band intensities of protein clusters at 31–97.4 kDa or a marker protein at ≈42 kDa, methods to quantify relative average degrees of channelization (RADC) in different maize backgrounds were developed. Using either method, Oh43 had the highest RADC and B73 had the lowest RADC among the inbred lines examined. Another method involves extraction of total proteins using 2% SDS containing 0.2% ME from granules with the majority of surface proteins removed. The extract is subjected to SDS‐PAGE and Western blotting, followed by location and quantification of the actin band using antibodies to maize pollen actin. These four methods give somewhat different results for six inbred lines of corn with a relatively narrow range of RADC. In an attempt to relate them to the actual number of observed pores (channel openings to the surface), granules were treated with α‐amylase to enlarge the pores, with and without prior treatment with a protease. We concluded that this treatment revealed something about the nature of the granules and the action of α‐amylase on them, but it was not an indication of the number of channels present. The outcome of this research provides evidence that the number of channels in corn starch granules varies with the genetic makeup of the parent plant. We concluded that measuring granule actin is the preferred method.     

An Economic Analysis of the Potential for Precision Farming in UK Cereal Production

The results from alternative spatial nitrogen application studies are analysed in economic terms and compared to the costs of precision farming hardware, software and other services for cereal crops in the UK. At current prices, the benefits of variable rate application of nitrogen exceed the returns from a uniform application by an average of £22 ha⁻¹ The cost of the precision farming systems range from £5 to £18 ha⁻¹ depending upon the system chosen for an area of 250 ha. The benefits outweigh the associated costs for cereal farms in excess of 80 ha for the lowest price system to 200–300 ha for the more sophisticated systems. The scale of benefits obtained depends upon the magnitude of the response to the treatment and the proportion of the field that will respond. To be cost effective, a farmed area of 250 ha of cereals, where 30% of the area will respond to variable treatment, requires an increase in crop yield in the responsive areas of between 0·25 and 1.00 t ha⁻¹ (at £65 t⁻¹) for the basic and most expensive precision farming systems, respectively.     

A Gas Chromatography Procedure for Determining Milled Rice Surface Lipid Content

Rice (Oryza sativa, L.) degree of milling (DM) is a quantification of the amount of bran that has been removed from kernels during the milling process. Historically it has been determined using a time-consuming continuous solvent extraction (CSE) procedure to measure the surface lipid content. The objective of this research was to develop a gas chromatography (GC) method for rice surface lipids. The GC procedure was highly correlated with several other methods for DM including a commonly used CSE procedure and it demonstrated repeatability within acceptable analytical limits. Other aspects in support of the utility of this procedure are that it requires a relatively small amount of sample, organic solvent, and technician time. Consequently, this GC method for rice surface lipids measurement is suitable for use in determining rice DM in cultivar development programs and studies that require the analysis of a large number of samples.     

A Method for Determining the Ultimate Fate of Synthetic Chemicals during Composting

? Pollution control workers have proposed composting as a bioremediation method for the cleanup of contaminated soil and for the detoxification of hazardous organic chemicals. However, decomposition (mineralization to CO₂ and H₂O) may not always be enhanced by composting, and transformation products of unknown risk may accumulate during composting. This paper presents a scientifically based scheme to determine the ultimate fate of synthetic materials in a composting environment, and for studying factors that may control the degradation of specific chemicals including herbicides (e.g., substrate bioavailability, enzyme concentrations, environmental conditions).     

Approaches for Modification of Starch Composition in Durum Wheat

Manipulation of starch composition in cereals and particularly in wheat is receiving increasing attention due to recognition of its important role in food and nonfood applications. The amylose/ amylopectin ratio influences the physicochemical properties of starches and nutritional value of derived end products. Identification of the key enzymes involved in the starch biosynthetic pathway has opened new avenues for altering the amylose and amylopectin content in durum and bread wheat. The granule bound starch synthases (GBSSI), or waxy proteins, are the enzymes responsible for amylose synthesis in storage tissues; amylopectin is produced by the concerted action of different enzymes, including starch synthases (SS), branching (SBE), and debranching enzymes (DBE). By altering the level of key enzymes involved in the regulation of starch synthesis, it is possible to generate novel starches with unique functional properties. In this respect, both low and high amylose starches are particularly interesting because they are associated with industrial and processing properties as well as with human health and nutrition. So far, major attention has addressed the manipulation of starch composition in bread wheat, whereas durum wheat has been investigated to a much lesser extent. Approaches currently available to alter amylose/amylopectin ratio and tailor starch composition in durum wheat are presented.     

用于食品传热分析的随机有限元方法

将随机有限元方法引进食品加工过程中传热方程的求解,以微波加热过程为例应用其基本思想,使用摄动方法分离方程并用有限元程序求得节点温度的时间历程,同时与Monto Carlo数字模拟方法的结果进行了比较,两者具有良好的一致性而随机有限元方法具有高得多的计算效率。该文还对食品参数的随机分布特征及由此而造成的微波加热过程中温度分布的随机特征进行了分析。