绿原酸对果汁加热过程中5-羟甲基糠醛形成的影响

绿原酸是水果中常见的酚酸,而5-羟甲基糠醛(5-hydroxymethylfurfural,5-HMF)是干制水果中含量较高的食品内源性污染物。将水果中绿原酸的主要组分3-咖啡酰奎尼酸(3-O-caffeoylquinic acid,3-CQA)添加到4种果汁中,在90℃下热处理48 h,以探讨绿原酸对水果热加工中5-HMF形成的影响。结果表明:3-CQA促进5-HMF形成。果汁中3-CQA浓度分别为0.5、5、50 mmol/L时,苹果汁中5-HMF含量分别增加23.5%、60.4%和115.6%;葡萄汁中的5-HMF分别增加5.6%、35.3%和74.5%;桃汁中的5-HMF分别增加12.5%、73.7%和199.8%;橙汁中的5-HMF分别增加22.0%、56.3%和125.0%。同时发现,3-CQA含量随着加热时间的延长而减少,其中35.8%的3-CQA转化为4-咖啡酰奎尼酸、5-咖啡酰奎尼酸、咖啡酸和奎尼酸,这些降解产物都促进5-HMF形成。     

Colour determination of beef juices as an indicator of beef cooking temperatures

Dominant wavelengths and other colour parameters of beef juices were investigated as predictors of maximum internal temperatures attained during beef cooking since beef imported by the USA from South American countries has to be cooked to a temperature compatible with the inactivation of the foot-and-mouth disease virus. Although the correlation between these parameters was highly significant, the prediction error was high and similar in magnitude to that obtained with other methods. However, according to the results obtained, a method was devised to evaluate if beef has been cooked to at least 79·4°C. Basically, the method consists in the visual comparison of the juice with a liquid standard of certain spectral characteristics. This method is simple and reliable for use at the port of entry or at the manufacturing plant. In doubtful cases the instrumental method described could be used to ascertain whether a certain temperature had been attained.     

果蔬汁品质的总抗氧化活性评价

通过对5种商品果蔬汁饮料和5种新鲜果蔬榨取的原汁的抗氧化活性、VC和总酚含量的测定和分析,结果表明,全体果蔬汁的总抗氧化活性与其所含的VC有着显著的相关性,与其所含的总酚量的关系很小。从保健功能的角度考虑,以总抗氧化活性作为果蔬汁品质的一项评价指标具有一定的参考价值和现实意义。     

国家技术监督局公布《橙、柑、桔汁及其饮料中果汁含量的测定》标准 于1997年10月1日开始实施

近来,随着人们对健康的关注程度明显提高,因此对天然食品或饮料的要求也日益提高,特别是果汁饮料。不少生产商便藉此生产各样伪劣假冒产品,在市场上鱼目混珠,使消费者蒙受损失。为了对这市场进行有效监控,国家技术监督局最近发布了一项果汁饮料中果汁含量的测定标准,作为依据。     

蜂蜜中5-羟甲基糠醛标准物质的研制

为适应蜂蜜行业检测标准的需求,采用液相色谱法和同位素稀释质谱法,对标准物质候选物蜂蜜中5-羟甲基糠醛的含量进行准确定量,在完成均匀性和稳定性实验的基础上,进行了不确定度评定,成功申报国家一级标准物质（GBW10080-10082）,并应用于实际的检测中。     

Degradation of 5-hydroxymethylfurfural during yeast fermentation

5-Hydroxymethyl furfural (HMF) may occur in malt in high quantities depending on roasting conditions. However, the HMF content of different types of beers is relatively low, indicating its potential for degradation during fermentation. This study investigates the degradation kinetics of HMF in wort during fermentation by Saccharomyces cerevisiae. The results indicated that HMF decreased exponentially as fermentation progressed. The first-order degradation rate of HMF was 0.693 × 10(-2) and 1.397 × 10(-2)min(-1) for wort and sweet wort, respectively, indicating that sugar enhances the activity of yeasts. In wort, HMF was converted into hydroxymethyl furfuryl alcohol by yeasts with a high yield (79-84% conversion). Glucose and fructose were utilised more rapidly by the yeasts in dark roasted malt than in pale malt (p<0.05). The conversion of HMF into hydroxymethyl furfuryl alcohol seems to be a primary activity of yeast cells, and presence of sugars in the fermentation medium increases this activity.     

Degradation of 5-hydroxymethylfurfural during yeast fermentation

5-Hydroxymethyl furfural (HMF) may occur in malt in high quantities depending on roasting conditions. However, the HMF content of different types of beers is relatively low, indicating its potential for degradation during fermentation. This study investigates the degradation kinetics of HMF in wort during fermentation by Saccharomyces cerevisiae. The results indicated that HMF decreased exponentially as fermentation progressed. The first-order degradation rate of HMF was 0.693?×?10^?2 and 1.397?×?10^–2?min^?1 for wort and sweet wort, respectively, indicating that sugar enhances the activity of yeasts. In wort, HMF was converted into hydroxymethyl furfuryl alcohol by yeasts with a high yield (79–84% conversion). Glucose and fructose were utilised more rapidly by the yeasts in dark roasted malt than in pale malt (p?<?0.05). The conversion of HMF into hydroxymethyl furfuryl alcohol seems to be a primary activity of yeast cells, and presence of sugars in the fermentation medium increases this activity.     

肉味香精中5-羟甲基糠醛的含量测定

目的建立肉味香精中5-羟甲基糠醛的高效液相色谱分析方法。方法香精样品经甲醇溶液提取后离心,将所得上清液过滤后采用高效液相色谱分析。测定条件为:Venusil XBP-C18色谱柱,UV检测器的检测波长为284 nm,以甲醇-水溶液(5:95,V:V)为流动相,流速为1.0 mL/min,柱温30℃。结果本方法能在25 min内完成目标化合物的分离分析。5-HMF标准品在0.16~40.00μg/mL的浓度范围内呈良好的线性关系,r~2=0.9999,方法的检出限为0.3525μg/L,定量限为2.82μg/L。5-HMF在3个添加水平的平均回收率为86.89%,能够满足样品测定的要求。自制糖醋排骨香精中5-HMF的含量为7.80 mg/kg,市售猪肉、牛肉和鸡肉香精中5-HMF的平均含量分别为3.94、5.32和9.38 mg/kg,且测定结果间的RSD平均值为均小于5%。结论该方法快速、准确、灵敏,适用于肉味香精中5-羟甲基糠醛的定量分析。     

食品中5-羟甲基糠醛的形成与控制

5-羟甲基糠醛(5-hydroxymethylfurfural,HMF)是食品热加工和贮藏过程中产生的内源性污染物,主要通过美拉德反应和己糖在酸性条件下脱水产生,其形成过程受反应底物种类、加热温度、反应体系p H、水分活度及金属离子等影响。HMF具有一定神经毒性、遗传毒性;摄入后在磺基转移酶作用下可转化为具有致癌毒性的羟甲基糠醛次硫酸,因而近年来HMF受到了国内外的广泛关注。本文综述了HMF形成的途径、影响因素和控制措施。     

HPLC法测定牛乳中5-羟甲基糠醛的含量

采用HPLC法测定牛乳中5-HMF含量,5-HMF的回收率可达到91.7%。在不同加工工艺乳制品中,UHT低乳糖奶中5-HMF含量为4.733μg/mL,分别是巴氏杀菌奶和UHT保鲜奶的19倍和10倍。     

硼钨酸盐催化果糖制备5-羟甲基糠醛的研究

以钨酸钠、硼酸为原料,利用常规溶液合成法制备硼钨酸盐K_8[BW_(11)O_(39)H]·13H_2O,借助傅里叶红外光谱仪(FT-IR)、扫描电镜仪(SEM)、程序升温脱附仪(NH_3-TPD)对其结构进行了表征,并将其应用于催化果糖脱水制备5-羟甲基糠醛(5-HMF),系统考察了各因素对反应性能的影响。结果表明:硼钨酸钾呈团聚体的不规则块状结构且具有一定的酸性,在反应温度150oC、反应时间150 min、催化剂用量20 mg、二甲基亚砜作为溶剂的条件下,5-HMF产率可达35.5%,且重复使用3次仍保持较高的活性。     

Evaluation of 5-hydroxymethylfurfural content in market milk products

ABSTRACT

5-Hydroxymethylfurfural (5-HMF) is a cyclic aldehyde formed during non-enzymatic browning reactions. In milk, it is, on the one hand, a contaminant, on the other, a quality indicator. The objective of this study was to evaluate the content and selected factors affecting the concentration of 5-HMF in cows’ milk and first infant milk. The content of 5-HMF in market milk varied widely, the average was 54.8 μg L^?1 (3.3–136.8). There was no significant difference in the concentration of this contaminant between UHT, HTST pasteurised and micro-filtered milk. It was also shown that the content of lipid components did not affect the concentration and kinetics of the 5-HMF formation in milk subjected to thermal treatment. Lactose-free milk was characterised by a level of this compound much higher than regular products. The 5-HMF average contents in powder cows’ milk and first infant milk were respectively 642 and 2315 μg kg^?1.     

Fluorimetric detection of protoporphyrins as an indicator for quality monitoring of fresh intact pork meat

In fresh meat production fast and non-destructive quality monitoring along the distribution chain is a key aspect to guaranteeing high quality and safe products for consumption. The applicability of fluorescence spectroscopy using protoporphyrins as indicators for meat ageing was investigated. Porcine musculus longissimus dorsi (MLD) was stored in slices over 20 days at 5 and 12 °C and measured every day with an excitation of 420 nm and an emission range of 550–750 nm. Additionally, pH, drip loss and colour were examined to assess possible correlations.The obtained spectra of the MLD showed an increase in three peaks at 592, 638 and 705 nm which could be reconstructed using the spectra of standard solutions of protoporphyrin IX (PP) and zinc protoporphyrin IX (ZnPP) or magnesium protoporphyrin (MgPP), respectively.Using principal component analysis (PCA) on the fluorescence spectral data, the meat slices stored at 5 °C showed differences in the fluorescence signal after the 10th day and 5th day when stored at 12 °C. An interrelationship between the additional analyses and the fluorescence intensities on these relevant days could not be established.In conclusion, the increase of ZnPP fluorescence due to temperature related changes of physiological meat properties is capable of serving as a quality indicator with regards to inadequate conditioning (e.g. during transportation and/or storage) of pork meat.     

Fluorimetric detection of protoporphyrins as an indicator for quality monitoring of fresh intact pork meat

In fresh meat production fast and non-destructive quality monitoring along the distribution chain is a key aspect to guaranteeing high quality and safe products for consumption. The applicability of fluorescence spectroscopy using protoporphyrins as indicators for meat ageing was investigated. Porcine musculus longissimus dorsi (MLD) was stored in slices over 20 days at 5 and 12 °C and measured every day with an excitation of 420 nm and an emission range of 550–750 nm. Additionally, pH, drip loss and colour were examined to assess possible correlations.The obtained spectra of the MLD showed an increase in three peaks at 592, 638 and 705 nm which could be reconstructed using the spectra of standard solutions of protoporphyrin IX (PP) and zinc protoporphyrin IX (ZnPP) or magnesium protoporphyrin (MgPP), respectively.Using principal component analysis (PCA) on the fluorescence spectral data, the meat slices stored at 5 °C showed differences in the fluorescence signal after the 10th day and 5th day when stored at 12 °C. An interrelationship between the additional analyses and the fluorescence intensities on these relevant days could not be established.In conclusion, the increase of ZnPP fluorescence due to temperature related changes of physiological meat properties is capable of serving as a quality indicator with regards to inadequate conditioning (e.g. during transportation and/or storage) of pork meat.     

Importance of juices in nutrition of infants and preschool and school children

The data on assortments and nutritional value of infant's juices are reviewed. Special attention is devoted to the disputable problem of the time when the juice is to be introduced to the infant diet. The necessity of further investigations on the quality criteria of juices for infant nutrition is emphasized. Modern data on nutritional value and physiological role of juices for preschool and school children are also presented. The perspectives of future investigations on the development and manufacture of new juices for infants and children are outlined.     

不同冷冻浓缩橙汁质量比较

对进口和国产的5个冷冻浓缩橙汁样品进行了分析,结果表明,国产橙汁的苦味重,酸度大,香气淡,而进口橙汁苦味淡,酸度适宜,香气较浓,因此进口橙汁的质量较好,但是国产橙汁Vc含量较高,两者的颜色差异不大。     

A cooking quality parameter as an indicator of adulteration of Basmati rice

Among various cooking quality parameters, differential length/breadth ratio has been found to be a reliable indicator of adulteration of Basmati rice, with Improved Sabarmati, Pusa-169, PR-106, Kali-much, Lakra and Parimal, which are the rice varieties used frequently for adulteration. A minimum value of length/breadth ratio of 3.92±0.09 to 4.09±0.09 was found to be indicative of pure Basmati.     

降低绵白糖中5-羟甲基糠醛含量的研究

研究了绵白糖生产用转化糖浆制备过程中影响5-羟甲基糠醛（5-HMF）形成、蔗糖转化率以及糖浆色值的因素,并通过正交试验,优化出酸法水解蔗糖生产转化糖浆的工艺条件,即糖浆锤度为75°B,pH值1．5,温度75℃,反应时间60min。在优化条件下每百克转化糖浆含有3．02mg5-HMF,糖浆色值为93．9IU,蔗糖转化率达到91．5％。