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。     

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。     

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.     

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。     

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。     

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.     

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.     

5-羟甲基糠醛在F-55果葡糖浆贮存过程中的变化研究

5-羟甲基糠醛(HMF)作为影响果葡糖浆风味的异味化合物之一,在贮存过程中的变化很可能直接影响到果葡糖浆制成品口感的好坏。研究了HMF在F-55果葡糖浆贮存过程中的变化情况,结果表明温度升高会导致HMF含量在40 d后达到最高峰。果葡糖浆在低温条件下贮存,且贮存期控制在40 d内,可减少HMF对糖浆质量的影响。     

高效液相色谱法测定老陈醋中的5-羟甲基糠醛

利用高效液相色谱法测定老陈醋中5-羟甲基糠醛(5-HMF)的含量,以5%甲醇水溶液为流动相,采用C18色谱柱,在284nm波长条件下检测样品中的5-HMF。结果表明,该方法快速、准确,在0.0143～0.1001μg范围内线性相关系数为R2=0.9994,平均回收率88.27%～96.69%,相对标准偏差为2.09%～4.70%。     

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％。     

Impact of enzyme on quality of blackcurrant and plum juices

The aim of work was optimization of technology of cloudy blackcurrant and plum juices production. The major concern was the increase of product cloudiness and its stability. Red fruit were processed with commercial pectinolytic preparations (Pectinex BE Colour, Pectinex BE XXL, and mixture of Rohapect PTE with Rohament PL). The effect of enzyme dose, maceration time and addition of ascorbic acid (in case of plum) on juices quality was investigated. Using single enzyme, either polygalacturonase or pectin lyase did not allow obtaining juices with high enough turbidity, however appropriate enzyme mixture allowed to obtain cloudy juice with the turbidity of at least 230 NTU for blackcurrant and above 500 NTU for plum juice. The best pressing-yield for blackcurrant was achieved with polygalacturonase and pectin lyase, 65 g/100 g after 1 h and 74 g/100 g after 4 h of pectinolysis. The macerating mixture gave about 58÷59 g/100 g yield, irrespectively of enzymation time. Pressing-yield of plum juices was in the range of 94÷97 g/100 g due to the fact that practically only skins were retained on pressing cloth. Addition of ascorbic acid (AA) during plum juice processing in quantity of 500 mg/kg had protective effect on anthocyanins. In control plum juices range of anthocyanins contents were 12.1÷16.5 mg/100 ml while in juice with AA addition even 21.4÷24.5 mg/100 ml.     

高效液相色谱串联质谱法测定红糖中5-羟甲基糠醛

建立了红糖中5-羟甲基糠醛的高效液相色谱串联质谱检测方法.红糖样品经甲醇-水(V/V=5/95)充分溶解提取,经HLB柱富集净化,氮吹干洗脱液,用乙腈-水(V/V=1/9)复溶,供高效液相色谱串联质谱仪检测.以甲醇和水为流动相梯度洗脱,用Phenomenex Luma Omega C18柱(1.6μm,100 mm×2...     

不同活性炭对果葡糖浆脱色性能及5-羟甲基糠醛吸附力的比较

5-羟甲基糠醛是影响果葡糖浆风味的异味物质之一,在果葡糖浆的生产工艺上无法完全去除,需要通过调节工艺参数得以控制。通过分析活性炭对5-羟甲基糠醛的吸附力及对糖浆的脱色效果,得出了不同工艺制造的粉状活性炭的优劣性,为果葡糖浆生产厂家活性炭的选择及添加比例提供参考。     

Complex approach to evaluation of natural quality of coloured juices

A novel multidimensional approach to estimation of fruit and berry colored juice authenticity is proposed. It includes determination of quality (determination of 5-hydroxymethylfurfurol) and authenticity (determination of organic acids, hydrocarbons, anthocyanin pigments and artificial colorants) parameters. Both experimental and literature data on chemical composition of 12 colored fruits and berries are summarized. New composition characteristics of pomegranate, bilberry, red currant, blackberry and lingonberry are presented.     

Re-evaluation of peroxide value as an indicator of the quality of edible oils

The oxidation of oils has important effects on the quality of oily foods, such as instant noodles. In particular, the generation of aldehydes, which accompanies the oxidation of oils, is one of the first factors to reduce food quality. We examined various indicators of oil quality during temperature-accelerated storage and found that peroxide value (POV) was highly correlated with the total concentration of major odorants. Moreover, the correlation of POV with the total concentration of five unsaturated aldehydes (t-2-heptenal, t-2-octenal, t-2-decenal, t-2-undecenal and t,t-2,4-decadienal) that show strong cytotoxicity was greater than the correlation of POV with the total concentration of major odorants. The maximum allowable concentration of the five aldehydes was calculated based on the 'no observed adverse-effect level' of the aldehyde that showed the highest cytotoxicity, t,t-2,4-decadienal, along with the human daily oil intake. We showed that it is useful to utilize POV as an indicator to control food quality and safety.