浓缩苹果汁生产中控制褐变的研究

对控制苹果浓缩汁生产过程中的褐变进行了研究,结果表明:维生素C和柠檬酸混合使用对PPO褐变抑制作用增强,当果浆的流速控制在8t/h￣9t/h,温度控制在85℃￣90℃时,果汁吸光度降低0.065;采用吸附柱法对果汁进行脱色的最佳工艺条件为真空度1.33×104 Pa;树脂高度36cm,经脱色后果汁的体积(V)与该体积流出液的吸光度(A)之间的关系为:A=0.158+0.255X-0.066X2,X∈[0,1.8L]。     

浓缩苹果汁生产中褐变因素及其控制措施的探讨

通过分析浓缩苹果汁的生产工艺,阐明了目前苹果汁生产中防止褐变的基本措施以及引起果汁后期贮藏发生褐变的原因。浓缩苹果汁的生产工艺基本消除了果汁贮藏期的酶促褐变,在贮藏期的褐变限于非酶促褐变,主要是Maillard反应和焦糖化反应。     

包装材料对苹果浓缩汁贮藏期非酶褐变的影响

研究了苹果浓缩汁贮藏过程中,3种包装材料对褐变指数(A420)、氨基态氮、还原糖和5-羟甲基糠醛含量的影响。结果表明,3种包装材料对苹果浓缩汁的非酶褐变阻遏作用玻璃瓶最佳;20d内,PE/TIE/PA/TIE/PE5层共挤蒸煮袋>PE(聚乙烯)袋;20d后,PE袋>蒸煮袋。     

混浊苹果汁加工过程中的酶促褐变及其防止的研究

将几种可用于食品的防褐变剂在苹果破碎时加入,考察了它们对苹果浆和苹果鲜榨汁的防褐变效果及它们之间的协同作用。半胱氨酸、抗坏血酸、曲酸、氯化钠和氯化钙都是较好的防褐变剂。在所测试条件下,抗褐变的能力（褐变抑制率）为:0.1％的抗坏血酸>0.1％的偏重亚硫酸钠>0.1％的曲酸>0.1％的氯化钙>0.005％半胱氨酸>0.1％氯化钠。它们抗褐变能力都表现为浓度依赖型,特别是抗坏血酸。柠檬酸在所测试条件下没有抗褐变效果。0.044％NaCl+0.0125％Vc的组合较经济且可使果汁40min不变色。果浆脱气可减缓其褐变;减小果汁及果浆与空气的接触面也可防止褐变。      

混浊苹果汁加工过程中的的酶促褐变及其防止的研究

将几种可用于食品的防褐变剂在苹果破碎时加入,考察了它们对苹果浆和苹果鲜榨汁的防褐变效果及它们之间的协同作用.半胱氨酸、抗坏血酸、曲酸、氯化钠和氯化钙都是较好的防褐变剂.在所测试条件下,抗褐变的能力(褐变抑制率)为0.1%的抗坏血酸＞0.1%的偏重亚硫酸钠＞0.1%的曲酸＞0.1%的氯化钙＞0.005%半胱氨酸＞0.1%氯化钠.它们抗褐变能力都表现为浓度依赖型,特别是抗坏血酸.柠檬酸在所测试条件下没有抗褐变效果.0.044%NaCl+0.0125%Vc的组合较经济且可使果汁40min不变色.果浆脱气可减缓其褐变;减小果汁及果浆与空气的接触面也可防止褐变.     

水蜜桃汁热处理过程中的非酶褐变

对水蜜桃汁热处理过程中褐变度(A420)以及还原糖、总酚、Vc、5-羟甲基糠醛(5-HMF)含量的变化进行研究,以确定水蜜桃热加工过程中的主要非酶褐变反应类型。研究表明,果汁的褐变度和5-HMF的生成量均随着加热时间的延长而增大,且温度越高,其变化速率越快。而桃汁加热过程中5-HMF的生成主要与Vc的降解有关。另外,果汁中糖的降解反应也对褐变起着重要的作用。     

浓缩苹果汁的褐变与控制措施

褐变是影响我国浓缩苹果汁出口的主要问题之一，通过分析浓缩苹果汁产生酶促褐变与非酶褐变的原因，阐述了目前防止苹果汁褐变的主要措施。基本上消除了浓缩苹果汁的褐变。     

On the production of glucose and fructose syrups from cashew apple juice derivatives

The cashew crop is an important agro-economic activity in many equatorial areas, although less than 10% of the cashew apple production is exploited industrially. This work focuses on two aspects: obtaining food-grade syrups from cashew apple juice and studying fixed bed adsorption dynamics to separate fructose from glucose. Syrups obtained by concentrating clarified cashew apple juice under vacuum showed similar characteristics to a reference food-grade syrup, with a higher content in fructose, which may contribute to a higher sweetening power with less caloric intake. Adsorption equilibrium studies were performed with synthetic solutions of fructose and glucose by frontal analysis under the concentration range found in the syrups (10-120 g/L) at 30, 40 and 60 °C, using the cation exchange resin Dowex MTO 99Ca. Fructose was more strongly adsorbed than glucose, with measured selectivities ranging from 1.50 to 2.25. Resistance to mass transfer was significant and thought to be due to resin crosslinkage. Glucose and fructose breakthrough curves using cashew apple syrup as feed were practically identical to those measured with synthetic solutions, which leads us to believe that high-fructose syrups may be readily obtained by using current continuous chromatographic units, such as SMB.     

Non-enzymatic browning and estimated acrylamide in roots,tubers and plantain products

Acrylamide has been discovered in foods, especially high carbohydrate foods that are dry-cooked (baked, fried or roasted) at high temperatures which also create the conditions for non-enzymatic browning. Baking, frying and roasting are common food preparation methods in Ghana. Fifteen different high carbohydrate foods in Ghana, that undergo dry-cooking, have been investigated for non-enzymatic browning and acrylamide production. The products that showed notable non-enzymatic browning and acrylamide levels include fried sweet potato, plantain chips from the fresh produce, with their respective non-enzymatic browning and acrylamide values as 0.095 ± 0.006 optical density (OD), 1043 ± 47.6 parts per billion (ppb); 0.034 ± 0.03 OD, 568 ± 22.9 ppb. Roots and tuber products had relatively high non-enzymatic browning and acrylamide levels while plantain products showed low levels of non-enzymatic browning and acrylamide.     

Non-enzymatic browning and ascorbic acid degradation of orange juice subjected to electroreduction and electro-oxidation treatments

Orange juice was submitted to electroreduction and electro-oxidation treatments prior to pasteurization and compared to a control juice for oxido-reduction potential (ORP), dissolved oxygen and ascorbic acid contents. Evolution of non-enzymatic browning reactions and ascorbic acid degradation was evaluated at 4, 21 and 37 °C storage temperatures. Electroreduction treatment of the juice at 6 V (cell length of 1.58 cm) created a substantial reducing reservoir as ORP decreased from + 161 to −406 mV and it decreased dissolved oxygen by more than 90% of its initial content while the ascorbic acid content was not altered. In contrast, the electro-oxidation treatment raised the final ORP of the juice by 15 to 20 mV, increased substantially the dissolved oxygen content and decreased significantly the ascorbic acid retention. Electro-oxidation treatment resulted in an increase of non-enzymatic browning reactions during storage. Both the control and electroreduced juice showed very similar trends in ascorbic acid degradation over the 3 months storage period whereas the anions, cations and amino acids profiles of the juice remain unchanged. Contrary to the control and electroreduced juices, the electro-oxidation process decreased severely the orange flavor intensity and character being characterized as musty with sour-bitter aftertaste.

Industrial relevance of electrolytic treatment to modulate the oxidation-reduction potential of comestible food systems

The limitation of shelf life imposed on comestible beverage systems (juice, beer, milk, wine, etc.) is an important and common issue for food manufactures and consumers. The shelf life is shortened by the time-dependent development of off-flavors, browning, change of colors, and deterioration of nutrients, caused by the oxidative reactions of chemical and nutrient components in the food systems. Consequently, the food is becoming unattractive to consumers. The electrochemical technique by means of an electrochemical cell has the potential in inhibiting or accelerating these deterioration reactions through reduction or oxidation of organic and inorganic compounds inherent to the products, as well as effectively controlling the oxygen content in the products. This technique can be used as an alternative to the deliberate addition of chemical compounds (sulfite and others reducing substances) to inhibit the deterioration reactions (electroreduction) as well as to accelerate the aging process of the comestible products via accelerated oxidation process (electro-oxidation).     

Degradation compounds of carotenoids formed during heating of a simulated cashew apple juice

The influence of organic acid and heating treatments on carotenoid degradation on a simulated cashew apple juice was assessed by high performance liquid chromatography coupled with a photodiode array and mass spectrometry detectors. A total of nineteen carotenoids were separated in unheated simulated cashew apple juice, with all-trans-β-cryptoxanthin and all-trans-β-carotene as the major ones. As a consequence of heating, five xanthophylls disappeared, whereas two new cis isomers and five epoxide or furanoid-derivatives were formed and the levels of all cis isomers increased. In addition, 12′-apo-β-carotenal was formed at 90 °C. Two oxidation compounds (12′-apo-β-carotenal and 5,6-epoxy-β-cryptoxanthin) were formed after β-cryptoxanthin heating at 90 °C in an aqueous-based system. In all systems, the amounts of total carotenoids lost were not compensated by those formed. These facts indicated that isomerisation and oxidation to both coloured and non-coloured compounds were the main reactions occurring during heating of carotenoids in aqueous-based and juice systems.     

椰子水腰果梨复合果酒的研制

以椰子水和腰果梨为原料,对椰子水腰果梨复合果酒的发酵工艺进行研究.通过中心组合试验设计和响应面分析优化发酵工艺.最佳工艺为发酵温度为20℃、SO2添加量为100mgkg、腰果梨汁添加量为8％.以最佳酿造工艺制成的椰子水腰果梨复合果酒酒体澄清透亮,香气清淡,风味独特.     

浑浊苹果汁加工中苹果PPO热失活条件的研究

研究了热处理苹果汁(加或不加防褐变剂)、苹果浆使其中的PPO完全及部分失活所需要的温度和时间。结果为:在90℃处理苹果汁15s可使其中的PPO完全失活,而对于苹果浆则需要90℃处理20s以上。加了防褐变剂的苹果汁经90℃处理10s可使其中的PPO完全失活;此外,经80℃处理30s以上虽不能使其中的PPO完全失活,但添加的防褐变剂及果汁自身的pH值可抑制残余的PPO从而防止酶促褐变的发生。70℃处理苹果汁40s不能防止其中的酶促褐变。     

菠萝果汁抑制香蕉加工过程中酶褐变的初步研究

对菠萝果汁抑制香蕉片和香蕉果浆的酶褐变效果进行了研究。以蒸馏水、pH3.9柠檬酸溶液、10mmol/L异抗坏血酸溶液、5mmol/L亚硫酸氢钠溶液、新鲜菠萝果汁和热处理菠萝果汁分别对香蕉片和香蕉果浆进行处理,然后在不同时间测定香蕉片和香蕉果浆的L值。结果表明,新鲜菠萝果汁和热处理菠萝果汁具有相同的酶褐变抑制效果,而且显著优于蒸馏水、pH3.9柠檬酸溶液和10mmol/L异抗坏血酸溶液,与5mmol/L亚硫酸氢钠溶液的效果相似;其抑制酶褐变的机理不是单一的抗坏血酸或低pH值或柠檬酸或蛋白酶的作用,可能是多因素综合作用的结果。     

Enzymatic browning reactions in apple and apple products

This review examines the parameters of enzymatic browning in apple and apple products that is, phenolic compounds, polyphenoloxidases, and other factors (ascorbic acid and peroxidases), both qualitatively and quantitatively. Then the relationships between intensity of browning and the browning parameters are discussed, including a paragraph on the methods used for browning evaluation. Finally, the different methods for the control of browning are presented.     

Quantitative modelling approaches for ascorbic acid degradation and non-enzymatic browning of orange juice during ultrasound processing

The objective of this study was to develop a deterministic modelling approach for non-enzymatic browning (NEB) and ascorbic acid (AA) degradation in orange juice during ultrasound processing. Freshly squeezed orange juice was sonicated using a 1500 W ultrasonic processor at a constant frequency of 20 kHz and processing variables of amplitude level (24.4–61.0 μm), temperature (5–30 °C) and time (0–10 min). The rate constants of the NEB and AA were estimated by a primary model (zero and first order) while their relationship with respect to the processing factors was tested for a number of models, i.e., second order polynomial, different types of Ratkowsky-type model, and an Arrhenius-type model. The non-monotonic behaviour of NEB has been described more accurately by the use of a polynomial model. The rate constants of AA were described by a similar type of model having a monotonic behaviour. A synergistic effect of temperature for different amplitudes on the rate constant of both NEB and AA was observed, while an antagonistic effect of amplitude on the rate of NEB was evident. The models with the best fit were integrated to produce contour plots for the combined amplitude and temperature. The constructed contour plots illustrate that low temperatures and intermediate amplitudes, i.e., 42.7 μm, result in lower NEB and AA deterioration and consequently better quality orange juice. The overall developed modelling approaches exploit quality data in order to identify the optimal processing regions for eliminating quality deterioration of orange juice during ultrasound processing which is of high importance to the food industry.     

橙汁非酶褐变机制及控制措施

阐述了橙汁非酶褐变的机制：美拉德反应、焦糖化反应、抗坏血酸的氧化分解和多酚类化合物氧化缩合反应。通过对橙汁原料选择、杀菌方式、贮藏方式、褐变抑制剂添加及加工中吸附树脂使用的分析,重点综述了在橙汁加工储藏过程中控制非酶褐变的措施。     

Polyphenol oxidase activity,phenolic acid composition and browning in cashew apple (Anacardium occidentale, L.) after processing

This study describes the extraction and characterisation of cashew apple polyphenol oxidase (PPO) and the effect of wounding on cashew apple phenolic acid composition, PPO activity and fruit browning. Purification factor was 59 at 95% (NH₄)₂SO₄ saturation. For PPO activity, the optimal substrate was catechol and the optimum pH was 6.5. PPO K_m and V_max values were 18.8 mM and 13.6 U min⁻¹ ml⁻¹, respectively. Ascorbic acid, citric acid, sodium sulphite and sodium metabisulphite decreased PPO activity, while sodium chloride increased PPO activity. Wounding at 2 °C and 27 °C for 24 h increased PPO activity but storage at 40 °C reduced PPO activity. Gallic acid, protocatechuic acid and cinnamic acid (free and conjugate) were identified in cashew apple juice. Cutting and subsequent storage at 40 °C hydrolysed cinnamic acid. 5-Hydroxymethylfurfural content in cashew apple juice increased after injury and storage at higher temperatures, indicating non-enzymatic browning.