Nonenzymatic Browning of Freeze-Dried Sucrose

The appearance of nonenzymatic browning products in sucrosebased systems (5-20%; pH 1-5) during freeze drying and during subsequent room temperature storage in the dry state was investigated. Results showed that following the completion of the primary sublimation stage of drying, sucrose hydrolysis to glucose and fructose was initiated. Glucose and fructose undergo further breakdown, and at the same time products which absorb in the UV (280 nm) were formed. A short time later observable brown colors are noted (absorbance at 400 nm). The extent of UV absorbance and brown color formation increased with decreasing sucrose concentration and decreasing pH in the initial solution.     

Stability of Trehalose, Sucrose and Glucose to Nonenzymatic Browning in Model Systems

The rate of nonenzymatic browning was compared in freeze-dried model systems containing lysine and glucose, sucrose or trehalose at pH 2.5 and a water activity of 0.33. Rate constants for brown color formation (A420) were from 200 to 2000-fold greater for the sucrose than for the trehalose system. Some rate constants for sucrose browning approached those for glucose, indicating that extensive hydrolysis had occurred. The results indicate that use of trehalose rather than sucrose may be of value in stabilizing some systems vulnerable to nonenzymatic browning.     

Modeling the Contribution of Sugars, Ascorbic Acid, Chlorogenic Acid and Amino Acids to Non-enzymatic Browning of Potato Chips

The contribution of potato constituents to color development in fried chips was evaluated using model systems. Soluble constituents of potato slices were removed using water and ethanol. Leached slices were infiltrated with pH 6.2 solutions containing sucrose, reducing sugars (glucose and fructose), ascorbic, chlorogenic and amino acids (asparagine and glutamine) in quantities typical for potatoes. Infiltrated slice composition was evaluated by HPLC. Slices were fried and the color measured. Reducing sugars showed linear association with L* and hue angle and quadratic relationship with chroma of chips. Ascorbic acid affected chip color at low reducing sugar levels (40 mg/100g tuber); sucrose also contributed to chip color development.     

Nonenzymatic Browning of Mozzarella Cheese

Mozzarella cheese was made with combinations of Streptococcus thermophilus nongalactose (Gal^?) and galactose fermenting (Gal⁺) strains and Lactobacillus helveticus (Gal⁺) and L. bulgaricus (Gal^?). Galactose was found in all Mozzarella cheese regardless of the culture used. The highest concentration was in cheese made with Streptococcus thermophilus Gal^?L. bulgaricus Gal^? combination with Streptococcus thermophilus Gal⁺Lactobacillus helveticus Gal⁺ having the least. Little if any lactose was found in any of the cheeses. The temperature and time during stretching of the curd inhibited fermentation of the residual galactose.Galactose accumulated in Mozzarella when either strain of Streptococcus thermophilus was used. The fermentation of accumulated galactose was the result of metabolism by Lactobacillus helveticus. There was a positive correlation between galactose content and brown color intensity when Mozzarella cheese was heated. A predictive test was effective in evaluating the browning tendency of cheese.     

New Imidazoles Formed in Nonenzymatic Browning Reactions

1,3-Bis(carboxymethyl)imidazole was identified in a model reaction mixture derived from glycine, glyoxal, and formaldehyde. The same compound was also found in the reaction of glycine with glyoxal. The structure of this compound was elucidated from the measured molecular, mass and ¹H-NMR and ¹³C-NMR spectral data and confirmed by X-ray crystallographic measurements. Similarly, a 2-methyl-, 4-methyl-, and 2,4-dimethyl-1,3-bis(carboxymethyl)-imidazole were formed in reactions of glycine with glyoxal or methylglyoxal and formaldehyde or acetaldehyde. These 1,3-symmetrically substituted imidazoles represent quite a new group of N-containing heterocyclic compounds originating in model systems containing amino acids and α-dicarbonyl compounds and probably also in natural systems.     

Nonenzymatic Browning in Dried Apples During Storage

This investigation into the effects of various treatments on nonenzymatic browning of dried apples determined that cysteine incorporation did not reduce browning during storage. Calcium treatment reduced rate of darkening but as Ca⁺⁺ concentration increased the effssects diminished. Manganese and tin compound addition was ineffective on product darkening. Packaging of dried apples with oxygen-scavengers markedly decreased product darkening during storage. About 20% of the nonenzymatic browning reaction occurring during storage was attributed to nonoxidative, or Maillard, reaction, and about 70% to oxidation.     

Nonenzymatic Browning in Apple Juice Concentrate during Storage

Rate of browning in Red Delicious and Granny Smith apple juice concentrates during storage was investigated. Color development at 65°, 70° and 75°Brix and storage temperatures of 5°, 20° and 37°C were compared over 120 days. Color deterioration occured at a faster rate in Red Delicious. Reaction at different concentration and storage conditions was exponential, following an Arrhenius-type dependence with temperature. Activation energy for a solids content of 65 - 75°Brix ranged from 16.4 - 19.3 Kcal/mole. Influence of juice variety on activation energy was negligible. Water activity results are in general agreement with those reported by other investigators. A satisfactory correlation to predict commercial concentrate browning has been obtained. All other things being equal, thermal history is a critical factor to obtain a lighter color concentrate.     

硫酸氨基葡萄糖非酶褐变的初步研究

将硫酸氨基葡萄糖样品分别在60、70、75、80℃下加热10h,测定加热过程中褐变指数、5- 羟甲基糠醛含量、硫酸氨基葡萄糖含量、pH 值的变化,用来表征非酶褐变进行的程度,将结果应用零级动力学方程拟合。结果表明,随着加热温度升高、时间延长,褐变指数、5- 羟甲基糠醛的含量逐渐增加,而pH 值和硫酸氨基葡萄糖的含量逐渐下降,硫酸氨基葡萄糖的非酶褐变反应符合零级动力学,褐变指数和5- 羟甲基糠醛含量变化的反应活化能分别为85.127、136.973kJ/mol,NaHSO3 对硫酸氨基葡萄糖的非酶褐变有一定的抑制作用。     

Nonenzymatic Nonoxidative Browning in Hydrolyzed Shelf-stable Concentrated Cheese Whey

The rate of brown color development in hydrolyzed concentrated cheese whey (HCCW), and in model systems of related composition, was studied. Degree of lactose hydrolysis was a relevant parameter controlling rate of color changes, both in modified whey or in related model systems. Added CaCl₂ had a strong inhibitory effect on caramelization browning in model systems in which no amino compounds were added. This inhibitory effect was less important in model systems containing whey proteins and in HCCW in which Maillard's browning is the main mechanism of darkening. Effects of pH and temperature were similar to that previously reported for nonhydrolyzed concentrated cheese whey, as well as for many model systems containing sugars and amino acids.     

Nonenzymatic Browning in Pear Juice Concentrate at Elevated Temperatures

The effect of temperature and soluble solids (°Brix) on nonenzymatic browning in pear juice concentrate was determined by following absorbance at 420 nm (A₄₂₀) over the temperature range of 50–80°C. Browning could be modeled as a zero order rate process with rates of 22.2 × 10⁻⁴ (45.2 °Brix), 36.9 × 10⁻⁴ (55.4 °Brix), 53.5 × 10⁻⁴ (65.1 °Brix) and 107 × 10⁻⁴ (72.5 °Brix) A₄₂₀· min⁻¹ at 80°C. Temperature dependence was described by the Arrhenius relationship with an average activation energy of 21.9 kcal · mole⁻¹. Formol titration indicated a 20% loss of amino acids during heating 4.4 hr at 80°C and no loss of carbohydrates was observed after any heating period.     

加工过程中添加剂对苹果汁非酶褐变的影响

加工过程中添加剂对苹果汁非酶褐变的影响很大。金帅苹果在破碎时加入EDTA－Na2、柠檬酸和CaCl2可减轻非酶褐变程度，最优化组合为0．03mol/L CaCl2 0.003mol/L EDTA-Na2 0.005mol/L柠檬酸（A420值为0．100）；而对于富士苹果其最优化组合为0．06mol/L CaCl2 0.006mol/L EDTA-Na2 0.005mol/L柠檬酸（A420值为0．075）；在富士苹果破碎时加入NaHSO3、Cys和VC亦可减轻非酶褐变程度，其最优化组合为0．001mol/LNaHSO3 380mg/mlCys 0.006mol/L VC(A420值为0．231）。     

Predicting Protein Quality of Corn-Soy-Milk Blends After Nonenzymatic Browning

CSM, a corn-soy-milk high-protein supplement for children, was exposed to high temperatures. Various degrees of nonenzymatic browning occurred, and product color ranged from yellow to dark brown. Progressively greater deterioration of protein quality as measured by protein efficiency ratio (PER) occurred with increasing color change as measured by Hunter color values. Protein quality was also estimated by the Tegrahymena pyriformis W bioassay and essential amino acid analysis. Linear relationships between PER, available lysine, and Hunter “L” values provided rapid methods for predicting protein quality. Correlation with PER was 0.95 using Hunter “L” and 0.88 using available lysine values. A color standard plate was developed to provide rapid field screening.     

香蕉汁储藏过程中非酶褐变的研究

本文探讨了香蕉汁储藏中非酶褐变的原因与动力学。结果表明还原糖与氨基化合物发生的Maillard反应是造成香蕉汁储藏期间非酶褐变的主要原因。经与一级动力学和零级动力学模型拟合，推测香蕉汁储藏期间的非酶褐变符合零级动力学方程，其发生非酶褐变的活化能为80．46kJ／mol。     

Nonenzymatic Browning and Chemical Changes During Grape Juice Storage

The effect of storage on juice concentrate from 2 red grape (Merlot and Criolla) and 1 white grape (Yellow Muscat) varieties on color and chemical composition, at temperatures ranging from 10 to 30 °C, was investigated. Color deterioration as A420 occurred at a faster rate in juice made with Merlot variety. The same was true when the pigment destruction as A520/420 was studied. Total reducing sugar, fructose‐to‐glucose ratio, and proline (the only significant amino acid present in grape juice) remained practically constant during storage. The hydroxymethyl‐furfural (HMF) buildup reaction proceeded faster in Criolla grape juice. Independent of variety, a detectable amount of HMF was produced only after 12 wk of storage at any temperature.     

苹果浓缩汁非酶褐变动力学及影响因素

通过检测苹果汁的色值(T440nm)、褐变指数(A420nnm)、氨基态氮、5- 羟甲基糠醛含量等指标研究加工过程对苹果汁褐变的影响以及在不同贮藏温度(5、20℃和37℃)下苹果浓缩汁(70.5°Brix)的非酶褐变速率。3 个贮藏温度下的苹果浓缩汁褐变速率均符合一级反应动力学模式,而且高温情况下褐变更明显。随着贮藏时间的延长,氨基态氮含量明显下降而5- 羟甲基糠醛含量上升,尤其是贮藏在37℃的苹果汁这一变化更明显。5- 羟甲基糠醛与果汁褐变效应呈指数关系,可以说明苹果汁在贮存中的褐变主因是发生美拉德反应,而且氨基态氮含量与果汁褐变效应的线性关系也验证了这一结论。在果汁的初始加工过程中,破碎、压榨、酶解、超滤、前巴氏杀菌等单元操作中美拉德反应并不明显;吸附操作可以去除果汁中的氨基态氮以及其他色素物质;而其他操作过程如浓缩和后巴氏杀菌则促进了美拉德反应,导致果汁氨基态氮含量明显下降。     

控制桃带果肉饮料非酶褐变的研究

本文确定了大久保桃和绿化３号桃中花青苷、无色花青苷的最大吸收波长，并研究了桃花青苷的ｐＨ值效应和温度效应。采用正交试验对控制桃带肉果汁饮料非酶褐变的工艺参数进行了筛选。     

复合薯片生产中的几个问题

经过近十年的发展,我国的复合薯片从无到有发展为一个制造业,形成了工艺研究,新产品开发,生产及流通管理的体系,但主要设备依赖进口。休闲食品行业还存在哪些问题,今后如何发展,是本行业专家及企业家十分关注的问题。 一、原材料质量控制 (一)衡量复合薯片原材料的重要指标 马铃薯粉是生产复合著片的主要原材料,控制马铃薯粉质量才能保证产品质量。生产企业必须从两方     

桃带肉果汁饮料在加工中非酶褐变原因的研究

采用通径系数进行统计分析，对大久保和绿化３号桃带肉果汁饮料在加工过程中非酶褐变的原因进行研究。结果表明，大久保桃带肉果汁饮料在加工中非酶褐变主要由花青苷变色引起；绿化３号桃带肉果汁饮料在加工中非酶褐变主要由抗坏血酸氧化褐变引起。