酶法水解乳糖与热处理偶联对牛乳Maillard反应的影响

旨在探讨乳糖水解程度及热处理方法与Maillard反应的关系,鲜牛乳用中性乳糖酶处理获得不同水解程度的低乳糖牛乳,然后对牛乳进行不同的热处理,处理后的样本进行Maillard反应程度评价。采用葡萄糖氧化酶法测定不同水解时间的牛乳中葡萄糖质量浓度和乳糖水解率,用高效液相色谱法和紫外分光光度法分别测定水解后牛乳经不同热处理后的糠氨酸和5-羟甲基糠醛(5-hydroxymethylfurfural,5-HMF)含量及牛乳褐变程度的OD值。结果表明,随着乳糖水解时间的延长,牛乳中的葡萄糖含量呈增加的趋势,葡萄糖质量浓度从0.00 mg/100 m L增加到1 721.33 mg/100 m L,但增加趋势逐渐变缓;乳糖水解率从0%增加到70.33%,水解时间2.0 h后的牛乳水解率达到了50%以上。糠氨酸含量呈上升的趋势(P0.05),水解时间在3.0 h以上并经75℃、30 min热处理的牛乳,糠氨酸含量超过了190 mg/100 g pro;水解时间为0.5 h及以上并经75℃、15 s热处理的牛乳,糠氨酸含量超过了12 mg/100 g pro。生鲜牛乳和水解后经75℃、30 min热处理的牛乳,均未检测到5-HMF,水解后经75℃、15 s热处理的牛乳,随乳糖水解时间的延长,牛乳中5-HMF含量增加显著(P0.05)。牛乳的褐变程度随乳糖水解时间显著增加(P0.05),且乳糖酶水解后75℃、30 min热处理的牛乳的褐变程度明显高于75℃、15 s热处理的牛乳。本研究结果说明,乳糖经过酶水解后的牛乳,长时间热处理会加重乳Maillard反应,影响乳的蛋白质品质。     

Evolution of available lysine and furosine contents in milk‐based infant formulas throughout the shelf‐life storage period

The evolution of the Maillard reaction (MR) by measuring the available lysine and furosine (FUR) contents in adapted and follow‐up powdered milk‐based infant formulas over the shelf‐life storage period, at 20 and 37 °C, was studied. Available lysine and FUR contents were determined by fluorimetry and high‐performance liquid chromatography respectively. Statistically significant differences were found between adapted and follow‐up infant formulas with respect to the available lysine and FUR contents. Available lysine contents decreased significantly throughout the storage time, and the contents at 37 °C were lower than at 20 °C. A statistically significant increase in FUR contents was observed during the storage period, with the contents being high at 37 °C than at 20 °C. A simple regression analysis between the available lysine and FUR contents during (a) the first year (b) the second year and (c) the two storage years was applied. The best correlations were obtained during the first year of storage. The results obtained show a clear MR evolution during the storage of infant formulas. Copyright © 2003 Society of Chemical Industry     

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     

An analytical approach to reveal the addition of heat-denatured whey proteins in lab-scale cheese making

A simple analytical procedure for the detection of self-aggregated heat-denatured whey proteins (HDWP) in model cheeses was developed. The principle of the approach lies in the solubilization of the cheese matrix by a sodium citrate solution (0.2 M, pH 7.0) resulting in the dissociation of the casein micelles and the insolubilization of HDWP aggregates, which are collected in the pellet after a centrifugation step. The reliability of the procedure was tested in lab-scale cheeses from peroxidase-positive pasteurized milk with different protein-based ingredients (microparticulated whey protein concentrate, milk protein concentrate, whey protein isolate and Ricotta cheese) at concentrations ranging from 0.2 to 1.2% protein (w/v on cheese milk). A linear relationship between the amount of the HDWP added to cheese milk and that recovered from model cheeses was observed. Heat-damage indicators, furosine and lysinoalanine, showed levels in the experimental cheese samples not related with added HDWP, but represented a source of information on the ingredients other than liquid milk. Overall, in the model cheeses, the proposed method was an easy-to-apply and reliable tool for the evaluation of the presence of HDWP-based products. Further investigation is required for the application to real cheeses and for the evaluation of possible interferences from proteolysis during ripening.     

不同烹饪方式对金枪鱼中美拉德反应产物的影响

目的探讨煎制、挂糊油炸、烤制和煮制4种烹饪方式对金枪鱼中美拉德反应的影响。方法研究4种家庭烹饪方式(煎、炸、煮和烤)对金枪鱼鱼块中糠氨酸、羧甲基赖氨酸(carboxy methyllysine,CML)、丙烯酰胺、荧光化合物和赖氨酸含量的作用,探究烹饪方法对美拉德反应产物(Maillard reaction products,MRPs)的影响,从MRPs安全性的角度比较金枪鱼4种家庭烹饪方式的安全性。结果煎制和挂糊油炸烹饪金枪鱼过程中,当鱼块中心温度≤80℃时,MRPs主要为糠氨酸;当鱼块中心温度达90℃时,MRPs中糠氨酸含量下降,荧光产物含量增加。4种烹饪方式中仅300℃条件下烤制10 min的金枪鱼块中有少量CML产生;中心温度达100℃的煎制烹饪、中心温度≥90℃的挂糊油炸烹饪和≥240℃烤制温度的烤制烹饪,均导致鱼块中少量丙烯酰胺产生。煮制烹饪的鱼块中中后期MRPs含量较少。此外,煎制、烤制和煮制均可导致鱼块中赖氨酸含量降低,但鱼块中心温度≤90℃的挂糊油炸烹饪,可使鱼块中赖氨酸几乎没有损失。结论综合对比4种烹饪方式,挂糊油炸可显著保持金枪鱼块营养品质,是值得推荐的一种金枪鱼烹饪加工方式。     

Furosine is a useful indicator in pre‐baked breads

There is increasing demand for pre‐baked bread. Bakers can meet consumer requirements for breads of specific flavour and colour by pre‐baking an amount of bread in the morning and completing the baking process in the afternoon. This type of product is of special interest to sandwich bars, restaurants and large communities. In order to obtain an indicator of utility to monitor the processing of pre‐baked bread, the browning indicators furosine, hydroxymethylfurfural (HMF) and glucosylisomaltol were analysed in two independent assays of bread pre‐baked at 175 °C for between 5 and 30 min. No furosine was detected in raw or fermented dough. In the pre‐baking stage, furosine increased from 1.5‐ to 5‐fold between 5 and 30 min. The furosine values obtained in the two independent experiments were similar. HMF and glucosylisomaltol were only detected after 15 min, which is the time period commonly used for processing by the industry. Thus, among these indicators, furosine is the only one with utility for monitoring the pre‐baking process. On the other hand, a study of the baking of pre‐baked bread at 220 °C showed that HMF and glucosylisomaltol can be used to monitor the latter process. Copyright © 2004 Society of Chemical Industry     

Presence of furosine in honeys

Nineteen commercial samples (with a shelf‐life of 2 years) and two artisanal samples (freshly collected and stored for 1 year respectively) of Spanish honeys were analysed for pH, protein content and furosine content. Most of the samples had pH values and protein contents within the limits reported in the literature. The presence of furosine was confirmed by comparison of its retention time with that of a furosine standard and by HPLC–MS. The level of furosine in the samples studied ranged from 4.32 to 13.62 g kg^?1 protein. The lowest furosine value was observed in the freshly collected artisanal sample. Heat treatment under severe conditions (90 °C for up to 135 min) increased the furosine content from 4.43 to 14.38 g kg^?1 protein. The results show that furosine seems to be a promising indicator to detect overheating during honey manufacture. © 2001 Society of Chemical Industry     

Evaluation of the furosine and homoarginine methods for determining reactive lysine in rumen-undegraded protein

Three samples of soybean meal (SBM), 3 samples of expeller SBM (SoyPlus, West Central Cooperative, Ralston, IA), 5 samples of distillers dried grains with solubles (DDGS), and 5 samples of fish meal were used to evaluate the furosine and homoarginine procedures to estimate reactive Lys in the rumen-undegraded protein fraction (RUP-Lys). One sample each of SBM, expeller SBM, and DDGS were subjected to additional heat treatment in the lab to ensure there was a wide range in reactive RUP-Lys content among the samples. Furosine is a secondary product of the initial stages of the Maillard reaction and can be used to calculate blocked Lys. Homoarginine is formed via the reaction of reactive Lys with O-methylisourea and can be used to calculate the concentration of reactive Lys. In previous experiments, each sample was ruminally incubated in situ for 16 h, and standardized RUP-Lys digestibility of the samples was determined in cecectomized roosters. All rumen-undegraded residue (RUR) samples were analyzed for furosine and Lys; however, only 9 of the 16 samples contained furosine, and only the 4 unheated DDGS samples contained appreciable amounts of furosine. Blocked RUP-Lys was calculated from the furosine and Lys concentrations of the RUR. Both the intact feed and RUR samples were evaluated using the homoarginine method. All samples were incubated with an O-methylisourea/BaOH solution for 72 h and analyzed for Lys and homoarginine concentrations. Reactive Lys concentrations of the intact feeds and RUR were calculated. Results of the experiment indicate that blocked RUP-Lys determined via the furosine method was negatively correlated with standardized RUP-Lys digestibility, and reactive RUP-Lys determined via the guanidination method was positively correlated with standardized RUP-Lys digestibility. Reactive Lys concentrations of the intact samples were also highly correlated with RUP-Lys digestibility. In conclusion, the furosine assay is useful in predicting RUP-Lys digestibility of DDGS samples, and the guanidination procedure can be used to predict RUP-Lys digestibility of SBM, expeller SBM, DDGS, and fish meal samples.     

Technological properties and non-enzymatic browning of white lupin protein enriched spaghetti

Spaghetti was prepared by replacing semolina with different amounts of lupin protein, in order to increase the protein content. A detailed investigation of the rheological properties of the dough and the cooking quality of pasta was performed in comparison to standard semolina spaghetti. Moreover, the effect of the addition of lupin protein on non-enzymatic browning was evaluated by measuring ε-furoylmethyllysine (furosine) and 5-hydroxymethyl-2-furancarboxaldehyde (HMF), which are considered useful indices of semolina quality and pasta processing conditions. Dried spaghetti fortified with 5% of lupin protein isolate has a colour and rheological features comparable with the semolina sample and also the behaviour during cooking results to be satisfactory. As far as the thermal damage is concerned, the furosine values of fortified spaghetti differ only marginally from standard pasta and the percentage lysine loss is quite small (ranging from 12.1% to 15.7%).