Chlorophyll, colour and pH changes in H.T.S.T. processed green pea puree

Summary. Pea puree of pH 6.95 and pH 8.45 was heat processed in thermal death-time tubes at temperatures between 115.6°C and 148.9°C to a process value of F₀= 6.0. Chlorophyll pigments, Hunterlab colour indices and pH were determined before and after high temperature-short time (H.T.S.T.) processing and during storage for 18 months at 20°C, 2.8°C, and −23.3°C.
Highly significant correlations were found between per cent conversion of chlorophylls to pheophytins and objective colour indices derived from tristimulus measurements on stored pea puree. the degree of chlorophyll conversion, and hence puree colour, were both markedly affected by process temperature, product pH, storage time and storage temperature, but long-term storage stability was achieved only by combinations of two or more variables.
Changes in pH of processed and stored puree were directly related to changes in pigments and colour, and it appears that pH control during processing and storage offers the most likely means of colour and pigment retention in heat processed chlorophyll-containing foods.     

Effects of pre‐freezing,puree content and pasteurisation regime on colour stability of strawberry nectar made from puree

BACKGROUND: Heat treatment during processing of strawberry products has been proposed to negatively affect colour stability. Moreover, the role of enzymes with respect to colour stability is ambiguous when consulting the existing literature. The aim of the present study was to investigate the impact of various processing parameters (pre‐freezing, puree content, pasteurisation temperature and heating time) on the colour stability and anthocyanin monomer and L ‐ascorbic acid contents of strawberry nectars made from puree. In addition, the effect of different enzyme activities on colour stability during storage of strawberry nectars was investigated. RESULTS: Pre‐freezing of strawberries before processing had a significant positive effect on the colour stability of nectars made from puree. No significant effect on colour stability was found for higher puree contents. Increasing both the pasteurisation temperature and the heating time had a significant positive effect on colour stability. Results showed that colour degradation during storage was mainly due to residual enzyme activities. The shelf‐life of strawberry nectar could be extended about fivefold by adding an enzyme inhibitor. CONCLUSION: The colour stability of strawberry nectar made from fresh puree may be improved to some extent by an appropriate pasteurisation regime. Enzymes play an important role in colour degradation during storage of the nectar. Inactivation of these enzyme activities, however, could not be achieved even after a heat treatment at 90 °C for 60 min. Copyright © 2008 Society of Chemical Industry     

Kinetics of colour and texture changes in Gulabjamun balls during deep-fat frying

Gulabjamun, a popular Indian milk sweet, is prepared by deep-fat frying of balls of dough made of khoa, wheat flour and baking powder, and subsequent dipping in sugar syrup. Kinetics of colour and texture changes in gulabjamun balls were investigated with regard to frying temperature (120, 130, 140 °C). Crust colour was evaluated in terms of CIELAB parameters L*, a*, b*, and ΔE, and rheological properties in terms of hardness, stiffness and firmness. Frying-induced surface browning was reflected in a decreasing lightness value L* as well as the ratio of yellow hue index b* and red hue index a* and total colour expressed in terms of ΔE, L* following a zero-order change whereas the other parameters, a first-order change. Increase in the texture parameters hardness and firmness followed zero-order reaction kinetics whereas stiffness rise followed a first-order reaction. The temperature dependence of reaction constants could be explained by the Arrhenius equation. Activation energy was also obtained for both the colour and texture changes, which were in the range of 24.5-77.6 kJ/mol. High correlations between colour and texture parameters were observed and it was concluded that L* alone could be used to predict the firmness of deep-fat fried gulabjamun balls.     

Effect of pasteurisation on sensory quality of natural soursop puree under different storage conditions

Pasteurisation effects on natural soursop (Annona muricata L.) puree were evaluated in terms of appearance, colour, flavour, odour, consistency and overall acceptability for 12 weeks. The packaging and storage temperature combinations used were laminated aluminium foil (LAF), lacquered can (LC) and high density polyethylene plastic bottle (HDPE) at ambient temperature (28–38°C), 15, 4 and −20°C. Results showed pasteurisation at 79°C for 69 s significantly improved the sensory colour, flavour, appearance and overall acceptability of the puree. Pasteurised puree packed in LAF at 4°C had the highest score for almost every attribute evaluated. Overall, all samples were found acceptable by judges during the 12 week storage period. The better stability, in terms of colour, consistency and flavour characteristics, of pasteurised puree packed in foil at 4°C than the frozen control could be an additional and cheap advantage for storage and transport.     

Colour in short-term thermo-mechanically densified veneer of various wood species

Effect of short-term thermo-mechanical (STTM) densification temperature and pressure on the surface colour of veneer of four wood species—alder (Alnus glutinosa Gaertn.), beech (Fagus sylvatica L.), birch (Betula verrucosa Ehrh.), and pine (Pinus sylvestris L.) as well as possible correlations among all determined colour parameters (L*, a*, b*, h, C* and ?E) were investigated. Veneer sheets were densified at temperatures of 100, 150 or 200 °C and pressures of 4, 8 or 12 MPa for 4 min. The results were compared with those of non-densified veneers. The colour change of the samples was evaluated by CIEL*a*b* and L*h*C* colour co-ordinate systems. The results indicated: the temperature and pressure of densification affected to a big extent the colour of the veneer samples, with the effect of densification temperature being more evident than that of pressure. After the densification process, the veneers darkened. Colour changes are most pronounced at the highest densification temperature of 200 °C and very small at the lower temperatures of 100 and 150 °C for all investigated wood species. The change in a* is more pronounced than the change in L* or b*. In general, alder and birch veneer samples are characterized by the highest values of total colour difference followed by pine and beech samples among the four species. The quadratic models can be used for the prediction of surface colour in the densification process. The results of this study indicate that it is possible to govern surface colouration of wood veneers during densification process on an industrial basis.     

Comparison of high pressure treatment and thermal pasteurization effects on the quality and shelf life of guava puree

The effects of high pressures and thermal pasteurization on the survival of microorganisms, enzyme inactivation and quality changes of guava puree during storage at 4°C were investigated and compared with untreated samples. After treatment at a pressure of 600MPa and 25°C for 15 min, the microorganisms in guava puree were inactivated to less than 10 cfu mL⁻¹ and the product exhibited no change in colour, pectin, cloud and ascorbic acid content as compared with fresh samples. The inactivation of enzymes in guava puree by thermal pasteurization was greater than by high pressures. The microbial count in guava puree reduced to 200 cfu mL⁻¹ and the product showed marked changes in viscosity, turbidity and colour when heated at 88–90°C for 24s. The content of pectin, cloud and ascorbic acid as well as colour in untreated and high pressurized (400MPa) guava puree gradually decreased, whereas these changes were not observed in pasteurized (88–90°C) and high pressurized (6000MPa) puree during storage at 4°C for 60 days. The guava puree treated at 600MPa and 25°C for 15 min retained good quality similar to the freshly extracted puree after storage at 4°C for 40 days.     

FLOW BEHAVIOR OF GUAVA PUREE AS A FUNCTION OF TEMPERATURE AND CONCENTRATION

Flow behavior of guava puree was determined with a tube viscometer. The puree samples (9.8-16.0° Brix) exhibited shear-thinning behavior. The flow behavior index of the power law model was nearly constant for all the samples over a temperature range of 25-60°C; its mean value was 0.43 with a standard deviation of 0.031. The apparent viscosity decreased with increase in temperature and the activation energy offlow was found to be 3.7 kcallg mole. The apparent viscosity increased as the concentration of the purees was increased; the increase was proportional to concentration raised to a power of 2.7. The Mizrahi-Berk model described well the flow data of the purees. The magnitude of the shear rate exponent was about 0.48, indicating that the purees were suspensions in shearthinning media.     

感应电场对连续流动蓝莓果泥理化特性的影响

采用非接触型感应电场(IEF)对蓝莓果泥进行连续加工,考察不同激励电压(100、150和250 V)、温度(65、75和85 ℃)下果泥阻抗和多酚氧化酶(PPO)活性随处理时间(9、18、27、30、36和45 min)的变化规律,并对比不同处理(鲜榨、常规热处理、IEF处理)后蓝莓果泥的色值、粒径分布、流变特性、风味和挥发性成分。结果表明,随着处理时间的增长和处理温度的升高,料液阻抗逐渐降低;250 V激励电压诱导形成的IEF对多酚氧化酶(PPO)的杀灭具有促进作用,经250 V、85 ℃和30 min的IEF处理后,蓝莓果泥 PPO活性完全丧失。IEF处理蓝莓果泥的L*和a*分别为30.37和6.42,显著高于鲜榨和常规热处理的果泥(P<0.05)。IEF处理的蓝莓果泥产品在粒径分布、黏度和风味上更接近鲜榨果泥。弱的感应电场/感应电流对蓝莓果泥中呈色物质、风味成分等具有一定的稳定作用,有利于减缓热处理导致的果泥颜色损失和风味变化。研究旨在为利用弱电效应实现果泥产品的高品质加工提供一定理论参考。     

Flow behaviour of carrot puree: modelling the influence of time,temperature and potato flakes addition

Rheological properties of carrot puree were investigated in the 1–1000 s^?1 shear rate range with the objective of modelling the influence of time, temperature and addition of potato flakes on the flow behaviour. Carrot puree exhibited a shear‐thinning behaviour that was well described by the Ostwald‐de Waele (Power Law) model with a flow behaviour index of 0.34 (±0.02) at 20 °C. The time‐dependent behaviour was characterised by a second‐order Structural Kinetic Model. The decay of the structural parameter with time was found to be independent of shear rate. The Arrhenius model was used to explain the effect of temperature in the range from 4 to 60 °C. The dry matter was increased by adding potato flakes (0–5%). A power law model (for the concentration) and the Arrhenius relationship (for the temperature) were combined to simultaneously describe the effects of temperature and concentration. This study provides essential data for equipment and process design.     

Evaluation of heat and oxidative damage during storage of processed tomato products. I. Study of heat damage indices

The evolution of heat damage during storage of tomato pulp, puree and paste was studied by accelerated aging tests. Heat damage indices—5‐hydroxymethyl‐2‐furfural (HMF), furosine and colour changes (ΔE)—were evaluated for tomato products stored at 30, 40 and 50 °C for up to 90 days. Furosine and ΔE values increased following pseudo‐zero‐order kinetics, and the higher the solid content of the products, the higher were the rate constant values. HMF formation followed pseudo‐first‐order kinetics in tomato pulp and pseudo‐zero‐order kinetics in puree and paste samples. Data show that heat damage reactions in tomato products proceed even at room temperature, and the kinetic model provided can be used to predict changes occurring during shelf‐life. © 2002 Society of Chemical Industry     

Kinetic Modelling of Colour Degradation in Tomato Puree (Lycopersicon esculentum L.)

The kinetics of colour (measured as Hunter ‘a’ value) degradation in tomato puree (Lycopersicon esculentum L.) has been studied over a temperature range of 50–120 °C (isothermal condition), and also during normal open pan cooking, pressure cooking and cooking in a newly developed and patented fuel-efficient ‘EcoCooker’ (non-isothermal condition). The degradation of colour as measured by Hunter ‘a’ value was found to follow first order kinetics. The temperature dependence of degradation was adequately modelled by Arrhenius equation. A mathematical model has been developed using the isothermal parameters obtained to predict correctly the losses of red colour from the time–temperature data of non-isothermal heating/processing method. The results obtained indicate a colour degradation of similar magnitude in all the three modes of cooking used in the study.     

超高压和热灭菌对芒果原浆品质影响的比较

对比分析了超高压(UHP)及热处理在达到商业杀菌要求的基础上对芒果原浆感官品质、营养成分及理化性质的影响。实验结果表明,随着压力值(300～500MPa)的上升菌落总数逐渐减少,超高压处理(450MPa,28℃,20min)及热处理(85℃,10min)条件下均可达到商业无菌;上述两种处理条件处理后芒果原浆pH、可溶性固形物含量与对照样差异不显著(P0.05);超高压处理样品的L*、b*值与对照样差异显著(P0.05),a*值与对照样差异不显著(P0.05),热处理样品的L*、a*、b*值与对照样相比差异均显著(P0.05),超高压处理样品更好地保持了原有色泽;超高压处理样品的还原型VC保留率达91.18%,远高于热处理;感官分析通过定量描述分析法对不同处理方式处理后的样品进行分析评定,结果表明,超高压处理样品在色、香、味等方面都接近对照样。因此,超高压技术不仅具有较好的杀菌效果,而且最大限度地保证了芒果原浆的品质。     

Change in colour and rheological behaviour of sunflower seed oil during frying and after adsorbent treatment of used oil

Improvement in colour and viscosity of used sunflower seed oil was studied because the reuse of recovered oil could provide considerable savings to food processors. In this study, 50 consecutive deep-fat fryings were done by using potato samples in sunflower seed oil at 170 °C. Significant changes in sunflower seed oil were observed during frying. Change in viscosity and Hunter colour parameters were investigated. These parameters were determined on oil samples taken periodically during frying, and after adsorbent treatment. A predetermined optimum adsorbent mixture (2% pekmez earth, 3% bentonite and 3% magnesium silicate by weight) was applied for colour and viscosity recovery of used oil. Both the adsorbent-treated and untreated used oils showed Newtonian behaviour. Significant increase in oil viscosity was observed during frying. Frying caused a decrease in Hunter L value and an increase in a, b and TCD values of used oil samples. Adsorbents improved the Hunter L, a and b values significantly as well as TCD values, but not the viscosity of the used oil. All the Hunter parameters and TCD followed zero order reaction kinetics. Good agreement was observed between calculated and measured data (r=0.986–0.996).     

A Comparative Analysis of Colour Measurements of the Seed Coat and Endosperm of Wheat Kernels Performed by Various Techniques

The results of this present studies show that the colour of the seed coat of wheat kernels can be determined by digital image analysis (DIA) instead of spectrophotometry. High linear correlations (p < 0.05) were found between colour measurements of the seed coat performed by these techniques. The colour on the cross-sections of wheat kernels was related to the colour of their seed coat. A high correlation was also observed between the colour of the seed coat and the colour of the endosperm of wheat kernels. In all measurements colour was described by the RGB, XYZ, and L*a*b* models. Colour indices, i.e. hue (h⁰) and saturation (S*) were also calculated.     

Influence of pumpkin puree and guar gum on the bioactive,rheological, thermal and sensory properties of ice cream

The effects of pumpkin puree and guar gum on the bioactive, rheological, thermal and sensory properties of ice cream were investigated. The addition of pumpkin puree increased total phenolic content, dietary fibre, and antioxidant activity. Appropriate models described shear thinning and thixotropic behaviours of all mixes. By either adding pumpkin puree or by increasing guar gum concentration, all rheological properties increased except the flow behaviour index. Adding pumpkin puree reduced the freezing point temperature, ice content, frozen water and glass transition temperature but it increased unfreezable water. Increasing guar gum concentration did not alter colour and firmness, whereas the pumpkin puree increased colour, intensity of fruit flavours and firmness.     

Non-enzymatic browning in peach puree during heating

Non-enzymatic browning in peach puree (11° Brix) due to extended thermal treatment was investigated. Absorbance at 420 nm, colorimetric parameters (CIE L*, a*, b* and ΔE*), content in sugars (fructose, glucose and sucrose) and hydroxymethylfurfural were used to estimate the extent of nonenzymatic browning during heating at high temperatures (80, 85, 90, 95 and 98°C) for 480 min. Zero and first order kinetics were applied to describe evolution of relative absorbance at 420 nm. Relative luminosity and sucrose content follow a first order kinetic. Colour difference was successfully adjusted to a model including two stages: the first one includes the colour formation and it follows a kinetic of order zero and the second includes the colour destruction and it follows a first order kinetic model. Both first and autocatalytical models can describe HMF formation. Parameter b* was significantly reduced with heating time, especially at higher temperatures, on the contrary parameter a* increases during heating. The Arrhenius model described well the temperature dependence of the reaction rate constant for all the parameters considered.     

Caucasian facial L* shifts may communicate anti-ageing efficacy

An ageing study was conducted to capture skin colour parameters in the CIELab system from Caucasians of both genders and all available adult ages. This study produced a linear correlation between L* and age for a Caucasian population between 20 and 59 years of age as follows: (L* value) = -0.13 × (Age in years) + 63.01. Previous studies have addressed age-related changes in skin colour. This work presents a novel consumer correlated quantitative linear model of skin brightness by which to communicate age-related changes. Two product assessment studies are also presented here, demonstrating the ability of anti-ageing products to deliver on objective and subjective improvements in skin brightness. It was determined to be possible to use the fundamental Caucasian L*-age correlation to describe product benefits in a novel quantitative and consumer-relevant fashion, through the depiction of a 'years back' calculation.     

苹果沙棘复合果泥配方优化及品质分析

以苹果和沙棘原浆为原料,可溶性固形物、褐变度、感官评分为评价指标,通过单因素、Box-Behnken响应面设计优化苹果沙棘复合果泥配方。同时采用顶空固相微萃取-气相色谱-质谱联用技术分析苹果沙棘复合果泥的香气构成。试验优化果泥配方:苹果浆为基料,添加沙棘原浆7%、白砂糖12%、果胶0.3%(均为质量分数),该配方所制备果泥样品可溶性固形物为33%,pH值为3.35,亮度值(L^*)为50.45、红绿值(a^*)为3.93、黄蓝值(b^*)为24.83,感官评分87分,色泽金黄、口感细腻、酸甜适口。香气构成分析结果表明,苹果沙棘复合果泥样品中共定性定量57种组分,主要包括醇类、酯类、醛类、酮类、萜烯类。香气活性值(odor activity value,OAV)大于1的组分包括1-辛烯-3-醇、芳樟醇、正己醛、2-辛烯醛等22种香气化合物,可赋予产品青香、柠檬、苹果、紫丁香和茉莉香气。与苹果果泥相比,苹果沙棘复合果泥增加了12种主体香气(OAV>1),果香和花香更浓郁。     

桃汁热处理过程中非酶褐变动力学研究

桃汁在热处理过程中极易发生褐变反应,通常将褐变度和色值L*作为评价桃汁褐变程度的指标。通过测定和分析桃汁在热处理（80、90 ℃和100 ℃）过程中的相关指标发现,桃汁的褐变度分别上升了0.185、0.221和0.276,L*值分别下降了4.22、5.74和7.53,Chroma值和Hue值在热处理过程中逐渐变小,褐变指数不断增大;用零级、一级和联合动力学模型拟合各指标的动态变化的研究发现,联合动力学模型可以更好地表示褐变度和色值的动态变化（R2＞0.823）;热处理过程中VC含量不断减少,符合零级反应动力学模型（R2＞0.894）;5-羟甲基糠醛含量不断增加,符合联合动力学模型（R2＞0.905）,且在各个热处理的温度条件下5-羟甲基糠醛的生成与褐变度的变化表现出二次项关系（R2＞0.940）。