Quantitative relations between farinogram area and new extensogram characteristics of wheat flour

In the analysis of farinographic curves, it has been determined that the farinogram area is a very reliable indicator of the quality of wheat flour, if it has been measured 12 min from the achievement of the maximum. In such a way, the dough development time, which can considerably influence the size of the farinographic curve, if it has been measured 15 min after the farinograph has been set in motion, has been eliminated. Quantitative relations between one of the most important characteristics of the farinogram – the farinogram area, and the determined dough characteristics related to dough quality which can be registrated by means of the extensogram, have been determined: , where A_far = farinogram area measured 12 min from the achievement of the maximum, E = dough extensibility, A = area of the extensogram, k′ = represents the farinographic area when the ratio unit value is $ \frac{{{\rm E}^2 }}{{\rm A}}$, k?′ = 4.18 and standard deviation s = 0.214. This determined relation gives a new approach to the farinographic curve interpretation and stresses the new importance of the farinograph as an instrument for physical testing of wheat flour quality.     

Effect of Soybean 7S Protein Fractions, Obtained from Germinated and Nongerminated Seeds, on Dough Rheological Properties and Bread Quality

Germinated soybean flour has been proposed for use in bread making as a product to improve bread quality when small amounts are added to wheat flour. However, it is not clear which soybean components promote this action, and how these components may influence bread quality. The aim of this work was to evaluate the effect of the addition of soybean 7S protein fraction obtained from germinated and nongerminated seeds in dough rheological properties (farinographic and extensographic) and bread quality, including loaf volume, texture (firmness, compression force, resilience), colour (L*, a*, b*), crumb grain structure (cell density, mean cell area, shape factor), and consumer acceptance (sensory analysis). Results showed that this protein fraction just slightly affects bread quality, since no significant changes (P > 0.05) on bread volume and texture were obtained. Only crust and crumb colour were affected in a small amount, and a coarser crumb structure was also observed when adding 7S protein obtained from germinated soybean at its highest concentration. As the proportion of protein increased in the flour, both kinds of 7S fraction (germinated and nongerminated) were related to the increment in water absorption, as well as to the increment in extensographic maximum resistance to extension, specifically when adding 7S protein obtained from nongerminated soybean seeds. These results showed that the 7S soybean protein, as obtained in this work, is not related to the reported loaf bread quality improving effect of this legume when it is added in small quantities.     

Develop Mechanistic Models of Transition Periods between Lag/Exponential and Exponential/Stationary Phase

A continuing goal in predictive microbiology is models directly based on physiological behavior. Buchanan et al.¹ hypothesized that (1) the curvilinear lag/exponential transition represents the variability of cells in the adjustment (t_a) and metabolic (t_m) periods, and (2) the exponential/stationary transition is determined by limiting nutrient diffusion rates. Nutritional shift trials were conducted to estimate E.coli K-12 growth. Lactase production time suggest that lactase gene translation occurs after completion of lag phase. Agitation rates and inoculum sizes both influenced the shape of the exponential/stationary phase transition. Monte Carlo simulations allowed the generation of sigmoidal growth curves while considering physiological events.     

Limitations of the Log-Logistic Model for the Analysis of Sigmoidal Microbial Inactivation Data for High-Pressure Processing (HPP)

This study identified limitations of the log-logistic model to evaluate microbial inactivation kinetics by high-pressure processing (HPP) including the need to assign a numerical value to “approximate” the undefined expression log₁₀ t?=?0 and the misinterpretation of its parameters due to a derivation flaw. Peer-reviewed HPP microbial inactivation data were adjusted to a sigmoidal equation (SIG), the original “vitalistic” log-logistic models (VIT-1, VIT-6), and two functions that did not follow the original derivation procedure (LOG-1, LOG-6). Their goodness of fit was determined utilizing the coefficient of determination (R ² ) and Akaike information criteria (AIC). The shape of the survival curve greatly influenced the performance of log-logistic models. VIT and LOG models performed equally when the kinetic curve showed a sigmoidal shape, and the numerical values of their parameter estimates were identical regardless of the log₁₀ (t?=?0) approximation. Conversely, most concave curves yielded inaccurate parameter estimates for all models. LOG-1 and VIT-1 performed best when log₁₀ t?=?0 was ?1 or ?2, whereas LOG-6 and VIT-6 yielded best results for values of ?3 to ?9. SIG ranked last for most datasets but occasionally performed best (Akaike weight factor w_AICi ?=?0.40–1.00) when microbial survival counts showed clear sigmoidal shapes. VIT models consistently displayed R ² ?≥?0.98, and their parameters can be interpreted within a “biological” context using the corrected derivation shown for LOG models. However, concave curves are more frequently observed for HPP microbial inactivation, and fitting the experimental data to log-logistic models deems unnecessary.     

Immobilized Glucose Isomerase Use in Mirin Production

The conversion of glucose in mirin (an alcoholic seasoning) to fructose using immobilized glucose isomerase (IGI) was studied in order to produce sweetened mirin without chill haze. The initial conversion velocity (C_m/t_m) with IGI was affected by temperature, pH, and ethanol concentration. This reaction was first order, for which the temperature coefficient (Q₁₀) over the range 20–55°C was 2.0. The value of C_m/t_m was a maximum at pH 8.0, and decreased with an increase in ethanol. Conversions carried out in a continuous column reaction system had C_m/t_m values 36 times higher than that in a batch system. Mirin treated with IGI did not form chill haze.     

A model of non‐isothermal degradation of nutrients,pigments and enzymes

Published isothermal degradation curves for chlorophyll A and thiamine in the range 100–150 °C and the inactivation curves of polyphenol oxidase (PPO) in the range 50–80 °C could be described by the model C(t)/C₀ = exp[?b(T)tⁿ] where C(t) and C₀ are the momentary and initial concentrations, respectively, b(T) a temperature dependent ‘rate parameter’ and n, a constant. This suggested that the temporal degradation/inactivation events of all three had a Weibull distribution with a practically constant shape factor. The temperature dependence of the ‘rate parameter’ could be described by the log logistic model, b(T) = log_e[1 + exp[k(T ? T_c)], where T_c is a marker of the temperature level where the degradation/inactivation occurs at a significant rate and k the steepness of the b(T) increase once this temperature range has been exceeded. These two models were combined to produce a non‐isothermal degradation/inactivation model, similar to one recently developed for microbial inactivation. It is based on the assumption that the local slope of the non‐isothermal decay curve, ie the momentary decay rate, is the slope of the isothermal curve at the momentary temperature at a time that corresponds to the momentary concentration of the still intact or active molecules. This model, in the form of a differential equation, was solved numerically to produce degradation/inactivation curves under temperature profiles that included heating and cooling and oscillating temperatures. Such simulations can be used to assess the impact of planned commercial heat processes on the stability of compounds of nutritional and quality concerns and the efficacy of methods to inactivate enzymes. Simulated decay curves on which a random noise was superimposed were used to demonstrate that the degradation/inactivation parameters, k and T_c, can be calculated directly from non‐isothermal decay curves, provided that the validity of the Weibullian and log logistic models and the constancy of the shape factor n could be assumed. Copyright © 2004 Society of Chemical Industry     

Changes in thermoluminescence properties of minerals separated from irradiated potatoes and garlic during long-term storage under different light conditions

The effect of different light conditions on the specificity and reliability of thermoluminescence (TL) analysis to detect irradiated samples (potatoes and garlic) during 2?years of storage was investigated. The silicate minerals separated from the nonirradiated samples provided a low-intensity TL glow curve with a maximum peak after 300?°C demonstrating the absence of an irradiation history. The TL glow curve from the irradiated samples provided easy discrimination with TL glow curves of high intensity and maximum peak in temperatures range of 160?C185?°C. The results were also confirmed by calculating the TL ratio (TL₁/TL₂) through normalization (re-irradiation) step. The key parameters of the TL analysis including the TL intensity, TL glow curve shape, and the TL ratio exhibited a time-dependent change. The bleaching effect of different light conditions was also significant, which was most prominent in the case of natural light with a prominent decrease in the TL intensity and ratio. The maximum TL glow peak also showed a shift towards the higher temperature. However, all irradiated samples, irrespective of the storage conditions and time, were easily discernable from the nonirradiated ones considering the shape and intensity of the TL glow curve.     

In Vitro and In Vivo Flavor Release from Intact and Fresh‐Cut Apple in Relation with Genetic,Textural, and Physicochemical Parameters

Abstract: Flavor release from 6 commercial apple cultivars (Fuji, Granny Smith, Golden Delicious, Jonagold, Morgen Dallago, and Red Delicious) under static conditions (intact or fresh‐cut samples) and during consumption of fresh‐cut samples (nosespace) was determined by proton transfer reaction mass spectrometry. Textural (firmness, fracturability, flesh elasticity, and rupture) and physicochemical (pH, acidity, and water content) properties of the apples were also measured. Static headspace analysis of intact fruits revealed Fuji and Granny Smith apples had the lowest concentration for all measured flavor compounds (esters, aldehydes, alcohols, and terpenes), whereas Red Delicious apples had the highest. Fresh‐cut samples generally showed a significant increase in total volatile compounds with acetaldehyde being most abundant. However, compared to intact fruits, cut Golden and Red Delicious apples had a lower intensity for ester related peaks. Five parameters were extracted from the nosespace data of peaks related to esters (m/z 43, 61), acetaldehyde (m/z 45), and ethanol (m/z 47): 2 associated with mastication (duration of mastication–t_con; time required for first swallowing event–t_swal), and 3 related with in‐nose volatile compound concentration (area under the curve–AUC; maximum intensity–I_max; time for achieving I_max–t_max). Three different behaviors were identified in the nosespace data: a) firm samples with low AUC and t_swal values (Granny Smith, Fuji), b) mealy samples with high AUC, I_max, t_swal values, and low t_con (Morgen Dallago, Golden Delicious), and c) firm samples with high AUC and I_max values (Red Delicious). Strengths and limitations of the methodology are discussed. Practical Application: Volatile compounds play a fundamental role in the perceived quality of food. Using apple cultivars, this research showed that in vivo proton transfer reaction mass spectrometry (PTR‐MS) could be used to determine the relationship between the release of volatile flavor compounds and the physicochemical parameters of a real food matrix. This finding suggests that in vivo PTR‐MS coupled with traditional physicochemical measurements could be used to yield information on flavor release from a wide range of food matrices and help in the development of strategies to enhance food flavor and quality.     

Changes on Dough Rheological Characteristics and Bread Quality as a Result of the Addition of Germinated and Non-Germinated Soybean Flour

The increasing interest in functional and healthy food products has promoted the use of germinated soybean flour in the manufacture of foods for human consumption. Considering the beneficial effects of soy and its germination, farinograph and extensograph were used to study the effect of adding defatted flour of germinated (32 °C, 72 h) or non-germinated soybean—at different dry protein ratios (0, 0.5, 1.0, 1.5%)—to wheat flour on: water absorption (WA), maximum consistency time (MCT), dough stability (S), maximum resistance to extension (R _max), and dough extensibility (L). Baking tests (straight-dough procedure) were also performed to evaluate the effect of this addition on bread characteristics: loaf volume, texture (firmness, compression force, resilience), color (L*, a*, b*), crumb–grain structure (cell density, mean cell area, shape factor), and consumer acceptance (sensory analysis). Addition of both kinds of soybean flours increased the values of farinographic parameters (WA, MCT, S), although they did not have significant effects (p > 0.05) on extensographic properties (R _max, L). Loaf volume and crumb color were improved as soy flour addition was increased, whereas crust color was not affected (p > 0.05). Texture analysis showed that the addition of soy flour produced breads similar or better than the control, whereas the addition of GSF produced a coarser crumb grain. No detectable differences were found among samples during the sensorial analysis. Germinated soybean flour was better to improve dough breadmaking properties.     

带有2个形状参数的Ball曲线和曲面的扩展

构造了一组带有2个参数的四次多项式基函数,分析了这组基函数的性质.基于基函数定义了带有2个参数的多项式曲线.所定义的曲线不仅具有Ball曲线的特性,而且在控制顶点不变的情况下,随着参数的取值不同,可产生不同的逼近控制多边形的曲线.三次Ball曲线和相关文献中的曲线均是该文所定义的曲线的特例.运用张量积的方法,将曲线推广到曲面.应用实例表明,定义的曲线和曲面为曲线曲面设计提供了一种有效地方法.     

Investigation of sorption isotherms of wheat germ for its effect on lipid oxidation

This research aimed to investigate the oxidation and sorption isotherm properties of wheat germ and to determine monolayer moisture content (m₀) in particular, because it has a limiting effect on lipid oxidation. This research comprised two stages. The first stage was the determination of sorption properties and m₀ at three temperatures (15, 25, and 35°C). The second stage of the research was to investigate lipid oxidation properties of stored wheat germ at two different temperatures (4 and 25°C) and m₀ for 28 days. As a result, it was determined that wheat germ has a Type II sorption isotherm, Halsey is the best fitting sorption equation, and the average m₀ is 4.25 g moisture per 100 g dry matter. Furthermore, the free fatty acid and peroxide value of wheat germ oil increased with increasing storage moisture content and temperature, determined as 12.63% and 5.01 mEqO₂/kg on average, respectively. In conclusion, storage of impermeably packaged wheat germ at low temperature and m₀ content is an applicable method for decreasing rancidity and prolonging shelf-life.     

When is simple good enough: a comparison of the Gompertz,Baranyi, and three-phase linear models for fitting bacterial growth curves

The use of primary mathematical models with curve fitting software is dramatically changing quantitative food microbiology. The two most widely used primary growth models are the Baranyi and Gompertz models. A three-phase linear model was developed to determine how well growth curves could be described using a simpler model. The model divides bacterial growth curves into three phases: the lag and stationary phases where the specific growth rate is zero (gm=0), and the exponential phase where the logarithm of the bacterial population increases linearly with time (gm=constant). The model has four parameters: N_o(Log₈of initial population density), NMAX(Log₈of final population density), tLAG(time when lag phase ends), and tMAX(time when exponential phase ends). A comparison of the linear model was made against the Baranyi and Gompertz models, using established growth data forEscherichia coli0157:H7. The growth curves predicted by the three models showed good agreement. The linear model was more ‘robust' than the others, especially when experimental data were minimal. The physiological assumptions underlying the linear model are discussed, with particular emphasis on assuring that the model is consistent with bacterial behavior both as individual cells and as populations. It is proposed that the transitional behavior of bacteria at the end of the lag phase can be explained on the basis of biological variability.     

THE COMPUTATION OF VISCOSITY AND RELAXATION TIME OF DOUGHS FROM BIAXIAL EXTENSION DATA 1

Stress (T) versus time (t) data were obtained for wheat flour doughs in lubricated, constant crosshead speed, uniaxial compression experiments. These data were then analyzed by using the Upper Convected Maxwell (UCM) Model with two parameters, a relaxation time (Λ) and a shear viscosity (η). The numerical solutions to the differential equation governing the behavior of the UCM model in this experiment can be very sensitive to the initial slope of the stress/time plots. This region of the curve, near t = 0, is most sensitive to experimental error. Best-fit values of Λ and η were thus computed for a given curve at a series of initial starting points, t_i, which were sequentially taken up the stress/time plots. There was considerable fluctuation in the best-fit parameters but, nevertheless, values of relaxation time and shear viscosity could be obtained that gave good agreement between computed and experimental stress/strain curves.     

Prediction by leaf analysis of nitrogen fertilizer required for winter wheat

In 1966 and 1967, 12 experiments on winter wheat tested five rates of N applied in spring as NH₄NO₃. Leaf samples comprising all the above ground vegetation were taken on two dates in spring between 31 March and 18 May from a fixed area of crop grown without fertiliser N; the dry matter yield (DM, kg/ha) and N content (%) were determined. Between the two dates, DM increased and leaf N content decreased. From the response curves for N applied and grain yield, the optimum rate of fertilizer N required for maximum grain yield was obtained. The latter was used as a test of soil N availability and compared with the following values (i) content of N (%) in leaves at each sampling and its rate of decrease—no significant correlation, (ii) yield of leaf DM (kg/ha) at first sampling—no significant correlation, (iii) leaf DM yield at second sampling, significant (r= -0.678), and also rate of increase in DM (kg/ha per day, r= -0.711), (iv) leaf N offtake (kg/ha N) significant at first sampling (r= -0.607), second sampling (r= -0.744) and also rate of increase in N offtake (kg/ha N per day, r= -0.670). Crop growth in spring was related to N supply and it was shown that DM yield, leaf N offtake and their respective rates of increase could be used to assess the availability of N in the soil and to predict the amount of N fertilizer required in spring to obtain maximum grain yield.     

Rheological properties of wheat flour and quality characteristics of pan bread as modified by partial additions of wheat bran or whole grain wheat flour

The use of bran and whole grain flour changes dough rheology and causes difficulties in manufacturing bakery products. The aim of this study was to analyse the influence of substituting refined wheat flour (WF) by wheat bran (WB; 5%, 10%, 20%, 30% and 40%) or whole grain wheat flour (WGWF; 10%, 20%, 30%, 40% and 50%) on dough rheological properties and pan bread quality characteristics. The addition of WB and WGWF increased water absorption and resistance to extension and decreased stability, extensibility and peak viscosity. Effects with WB were more pronounced. The presence of WB or WGWF increased crumb moisture content, firmness and hardness and decreased specific volume of pan bread. It is important to set new farinographic and extensographic standards when using WB and WGWF, allowing for a correct correlation between rheology and quality characteristics of bakery products, as the same standards used for WF are not valid.     

面粉中胚芽含量对面团流变学特性及馒头品质的影响研究

在小麦面粉中添加同种小麦提取的胚芽所制成的胚芽粉,测定其面团流变学特性及降落数值,并做馒头感官评价试验。实验表明,拉伸面积、最大拉伸阻力、拉伸阻力、拉伸比例、稳定时间和粉质质量指数与胚芽添加量呈显著线性负相关;弱化度与胚芽添加量呈显著的线性正相关;降落数值、形成时间与胚芽添加量线的相关性不显著。在一定添加范围内(0～2%)馒头总评分随胚芽粉添加量增大而增大,超过此数值则馒头总评分随添加量增加而减小;馒头的麦香味也有此趋势。     

Sensitivity Analysis for Hygrostress Crack Formation in Cylindrical Food During Drying

A parametric analysis was performed to examine the influence of several factors on stress crack formation in cylindrical food during drying using a previously developed, validated simulation method. They included initial food moisture (W_o), air humidity (R_h) and temperature (T_a), convective surface mass transfer coefficient (h_m), convective surface heat transfer coefficient (h_t), moisture diffusivity (D_w), and initial food diameter (d_o). R_h influenced most strongly drying time for crack formation (t_cf), followed by T_a and W_o. The other 4 parameters in descending order of influence were h_m, h_t, d_o and D_w. The influence of all parameters, except W_o, was due to their influence on mass transfer Biot number, Bi_m, that was closely related to moisture concentration gradient in food. The influence of W_o was due to increased critical stress for crack formation with a reduced moisture level.     

Characterization and Quantification of Zinc Oxide and Titanium Dioxide Nanoparticles in Foods

There has been growing concern in recent years about contamination of foods by engineered nanoparticles (NPs) due to their increasing applications in food packaging materials, pesticides, and other products. In this study, we report a systematic approach to detect, characterize, and quantify engineered NPs (i.e., zinc oxide (ZnO) and titanium dioxide (TiO₂) NPs) in food products. A series of concentrations of ZnO and TiO₂ NPs from 0.05 to 1 wt% were spiked into corn starch, yam starch, and wheat flour. The presence of engineered NPs in foods was detected and measured by scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy and transmission electron microscopy. The average sizes of ZnO and TiO₂ NPs were around 38 and 40 nm in diameter, respectively. Most ZnO NPs were in either spherical or rod-like shape, while most TiO₂ NPs were in a spherical shape. The concentrations of engineered NPs in food samples were measured by inductively coupled plasma optical emission spectrometry. Calibration curves were plotted for quantification of NPs in foods (R ²?=?0.984 and 0.995 for ZnO NPs in corn starch and wheat flour, respectively; R ²?=?0.992 and 0.998 for TiO₂ NPs in yam starch and wheat flour, respectively). The results of this study could help develop systematic methodologies for detection, characterization, and quantification of NPs in food matrices.     

Ohmic heating of peaches in the wide range of frequencies (50 Hz to 1 MHz)

Abstract: The ohmic heating (OH) rate of peaches was studied at fixed electric field strength of 60 V.cm⁻¹, square-shaped instant reversal bipolar pulses, and frequencies varying within 50 Hz to 1 MHz. Thermal damage of tissue was evaluated from electrical admittivity. It showed that the time for half disruption (τ_T) of tissue was required more than 10 h at temperatures below 40 °C. However, cellular thermal disruption occurred almost instantly (τ_T < 1 s) at high temperatures (> 90 °C). Electrical conductivity σ_o and admittivity σ_o* of tissue at T_o= 0 °C and their temperature coefficients (m, m*) were calculated. For freeze–thawed tissues, σ and σ* as well as m and m* were nearly indifferent to the frequency. However, for the intact tissue, both σ_o, σ_o* and m, m* were frequency dependent. For freeze–thawed product, the power factor (P) was approximately equal to 1 and indifferent to the frequency and temperature. On the other hand, strong frequency dependence was observed for intact tissue with the minimum P approximately equal to 0.68 in the range of tens of kHz. The time required to reach a target temperature t_f was evaluated. The t_f increased with frequency up to the middle of the range of tens of kHz and thereafter continuously decreased. Samples exposed to the low-frequency electric field demonstrated faster electro-thermal damage rates. The textural relaxation data supported more intense damage kinetics at low-frequency OH. It has been demonstrated that a combination of high-frequency OH with pasteurization at moderate temperature followed by rapid cooling minimizes texture degradation of peach tissue. Practical Application: In this study, we investigated the electric field frequency effect on the rate of OH of peaches. It was shown that the time required for reaching the target temperature is strongly dependent upon the frequency. Samples exposed to low-frequency OH demonstrated higher electro-thermal damage rates. It has been shown that the combination of high-frequency OH with pasteurization at moderate temperature followed by rapid cooling minimizes texture degradation of peach tissue. Obtained results provide new information on the impact of electric field frequency on OH, which is useful for OH process design.     

可转位式转子槽粗铣刀的廓形设计探讨

本文讨论了可转位式阴转子槽粗铣刀的廓形拟合问题。这种铣刀是将圆柱形硬质合金刀片按切向倾斜安装在盘形刀体上,切削时圆弧刀刃在选定点的基面内的运动轨迹为椭圆,利用电子计算机可求出刀片的最佳安装位置,使椭圆曲线逼近理论廓形,误差在允许范围之内。