关于利用水解残液水解法除戊醣试验

关于提高蔗渣富强纤维浆粕质量的问题,目前在工业生产上普遍存在成品浆粕戊醣含量较高。我们根据酸水解的原理,曾采用水解残液做水解介质进行预水解,探索降低浆粕戊醣的研究,分别用水解残液和清水做水解介质进行水解比较除去戊醣的情况;入锅水解介质的酸浓度对除去戊醣的影响;水解残液累次循环使用(即后一次水解使用前一次水解残液做水解介质),看其是否会产生不良影响;不同水解介质水解后所做的     

CaO、NaOH对铬革屑水解效果的对比

以制革废弃物铬革屑为原料系统研究了CaO、NaOH水解革屑过程中碱用量、水解温度、水解时间、固液比对水解效果的影响,并通过水解率、水解度、特性粘数、铬含量等指标对水解产物进行表征,研究不同碱水解革屑的规律和差异。研究发现,两种碱水解铬革屑的过程相似,实验条件对水解收率的影响主次顺序为:碱用量温度时间液比;氧化钙水解革屑最高水解收率工艺条件为:氧化钙用量8%、水解温度90℃、液比为10、水解时间5 h,收率达到73%;氢氧化钠水解革屑最高水解收率工艺条件为:氢氧化钠用量10%、水解温度80℃、液比为6、水解时间3 h,收率为86%;氢氧化钠水解铬革屑的水解率较高,所得水解液分子量较小,但氧化钙水解革屑的脱铬率较高。     

鸡骨蛋白酶解工艺研究

本文采用木瓜蛋白酶水解脱脂后的鸡骨粉,以蛋白质水解度为评价指标,通过正交试验考察了酶浓度、底物浓度、水解温度和水解时间对水解效果的影响,确定最佳水解条件为：酶浓度7 500U/g,底物浓度5%和水解时间3 h。在该条件下水解,水解度可以达到32.1%。     

盐酸水解方法对鸡肉中氨基酸含量的影响

摘 要: 目的 研究盐酸水解过程中, 水解时间和添加巯基乙醇和苯酚保护剂对鸡肉中18种氨基酸含量的影响, 确定获得鸡肉氨基酸最高含量的盐酸水解方法。方法 以30个鸡胸肌(3种鸡、每种10个)为实验对象, 设计6个水解时间, 研究盐酸水解时间对鸡肉样品中18种氨基酸含量的影响, 确定获得氨基酸最高含量的盐酸水解时间。在上述研究的基础上, 随机选择6个鸡胸肌(3种鸡、每种2个)为实验对象, 设置3个水解时间, 研究巯基乙醇和苯酚对鸡肉样品中18种氨基酸含量的影响, 最终确定获得鸡肉中18种氨基酸最高含量的盐酸水解方法。结果 缬氨酸(valine, Val)和异亮氨酸(isoleucine, Ile)的最佳水解时间为24或26 h, 两水解时间无显著性差异(P>0.05); 其余16种氨基酸的最高含量均在22 h; Ile的含量在盐酸水解法水解24 h显著高于20 和22 h(P<0.05), 但在苯酚+盐酸水解法水解22h含量最高; 天冬氨酸(aspartate, Asp) 的含量在巯基乙醇+盐酸水解法水解22 h显著高于20 和24 h(P<0.05), 但在盐酸水解法水解22h含量最高; 甘氨酸(glycine, Gly)、丙氨酸 (alanine Ala)、酪氨酸(tyrosine, Tyr) 和苯丙氨酸 (phenylalanine, Phe)的含量在苯酚+盐酸水解法水解22 h显著高于20 h(P<0.05), 但水解22与24 h之间无显著性差异(P>0.05), 其中, Gly在苯酚+盐酸水解法水解22 h含量最高, Ala在盐酸水解法水解22 h含量最高, Tyr和Phe在巯基乙醇+盐酸水解法水解22 h含量最高; Val在盐酸水解法水解24 h含量最高, 脯氨酸(proline, Pro)和赖氨酸 (lysine, Lys)在苯酚+盐酸水解法水解22 h含量最高, 亮氨酸 (leucine, Leu) 在巯基乙醇+盐酸水解法水解22 h含量最高; 其余氨基酸在不同水解方法及水解时间中均无显著性差异(P>0.05), 但都在盐酸水解法水解22 h时含量最高。结论 巯基乙醇和苯酚对鸡肉中的含硫氨基酸无保护作用, 获得鸡肉中18种氨基酸最高含量的盐酸水解方法是盐酸水解法水解22 h。     

酶法水解制备鲅鱼可溶性肽的工艺研究

为确定木瓜蛋白酶水解鲅鱼的最佳条件,为低值小鲅鱼的开发利用奠定基础。采用木瓜蛋白酶水解脱脂后的鲅鱼粉,以蛋白质水解度为评价指标,通过正交试验考查了酶浓度、底物浓度、水解温度和水解时间对水解效果的影响。确定最佳水解条件为：酶浓度5 000U/g,底物浓度5%,水解温度50℃和水解时间6h,在该条件下水解,水解度可以达到33.21%。在此工艺条件下,鲅鱼蛋白水解效果较好,且水解液色泽较浅,有浓郁的鱼香味。     

不同水解方式对乳清浓缩蛋白水解产物结合钙量的影响

研究了酸水解和酶水解两种不同水解方式对乳清浓缩蛋白(WPC)水解产物与钙离子结合量的影响。结果表明,采取不同水解方式水解乳清浓缩蛋白,水解产物与钙离子结合能力不同,当酸水解与酶水解达到相同水解度时,酸水解比酶水解水解产物结合的钙量高;就酶水解而言,胰蛋白酶比枯草杆菌中性蛋白酶水解产物结合的钙量低。这一结果说明:乳清浓缩蛋白在酸水解形成纳米纤维的过程中会生成能够与钙离子结合的基团,与酶水解相比其钙结合量更高可能与WPC纳米纤维自身特殊结构有关。     

α-淀粉酶对辛烯基琥珀酸酐水解玉米淀粉影响

以玉米淀粉为原料,研究α-淀粉酶对辛烯基琥珀酸酐水解淀粉影响。通过水解单因素实验,结果显示,辛烯基琥珀酸酐淀粉水解反应随水解温度升高,淀粉酶量可提高淀粉水解程度,反应时间延长(从30 min到60 min较为明显)水解DE值逐渐升高。通过水解响应面分析实验,结果显示,加酶量与水解温度、水解温度与水解时间之间交互影响作用...     

豆渣酸水解工艺条件的研究

采用酸水解法水解豆渣,研究水解温度、水解时间、HCl溶液添加量与原料比值(mL/g)3个因素对豆渣水解率的影响,并确立了豆渣酸水解的最佳工艺条件.结果表明,水解温度90℃,水解时间5 h,HCl溶液添加量与原料比值(mL/g)2.75:1为最佳水解条件,在此条件下豆渣的水解率为58.02%.     

杜氏盐藻蛋白水解工艺研究

采用木瓜蛋白酶水解经乙酸乙酯脱脂后的杜氏盐藻粉,以水解度(DH)为指标,考查底物浓度、酶用量、水解温度、水解时间对水解度的影响。通过响应面分析法,所得最佳水解工艺条件为:底物浓度3.5%,酶用量5600U/g,水解温度为60℃,水解时间3.5h。在此条件下,得到最大水解度为13.19%。从而验证了木瓜蛋白酶水解杜氏盐藻蛋白工艺的可行性,为功能性多肽的开发利用提供一定理论依据。     

酶水解法提高大豆蛋白水解度的研究

用蛋白酶水解方法提高大豆分离蛋白水解度.通过对多种蛋白酶的对比分析可知,风味蛋白酶的水解效果好于其它蛋白酶,但正交试验结果表明,即使在优化条件下水解,单一的风味蛋白酶水解所得大豆分离蛋白水解度最高只达到43.12%.若先用胃蛋白酶水解再用风味蛋白酶水解则水解度最高可达68.81%,而风味蛋白酶与其它酶的联合应用效果略差;若先使用风味蛋白酶后使用胃酶则水解度只有47.89%.表明不同酶对大豆蛋白分子具有不同的水解特点.     

酸水解法从咖啡渣中制取D-甘露糖工艺研究

本文介绍咖啡渣在酸性条件下水解制取D -甘露糖的实验原理和操作方法 ,以及最佳条件温度 ,水解时间和酸度等工艺条件对糖的产率的影响     

Pretreatment processes assisted subcritical water hydrolysis for valorisation of spent coffee grounds

This study investigated the effect of sequential extraction techniques and pretreatment methods in enhancing the recovery of high-value products from spent coffee ground. Supercritical carbon dioxide (SC-CO₂) deoiling was performed to recover non-polar lipids, and subcritical water (SCW) hydrolysis of deoiled spent coffee ground (SCG) was conducted involving pretreatment with ultrasound (US-SCG), and sample particle size reduction (PS-SCG). SCW temperature, solid/liquid mixing ratio, constant pressure and residence time were studied for their effect on extracting reducing sugars (RS), total phenolic content (TPC), total flavonoid content (TFC), 5-HMF, and furfural. Temperature increase enhanced hydrolysis efficiency and promoted RS dehydration into 5-HMF and furfural. At 180 °C and 40 mg/600 mL, TPC, TFC and RS values increased significantly with ultrasound pretreatment correlating with improved antioxidant activities by DPPH and ABTS assays. Highest amount of 5-HMF and furfural was obtained at 210°C (highest temperature studied) with 44.71 and 2.36 mg/100 g. Chlorogenic acid recovery was the highest in the non-deoiled SCG (15.07 mg/100 g), with no significant difference observed in PS-SCG, suggesting an increase due to its reduced particle size. The results of this study provide comprehensive knowledge on the combined effects of integrated engineering systems to boost the valorisation of SCGs into high-value products.     

Sustainability issues along the coffee chain: From the field to the cup

The coffee industry is one of the most important commercial value chains worldwide. Nonetheless, it is also associated to several social, economic, and environmental concerns that impair its sustainability. The present review is focused on these main sustainability concerns from the field to the coffee cup, as well as on the strategies that are being developed and/or implemented to attain sustainability and circular economy principles in the different chain segments. In this context, distinct approaches have been applied, such as sustainable certifications (e.g., voluntary sustainability standards), corporate sustainability initiatives, direct trade, relationship coffee concepts, geographical indication, legislations, waste management, and byproducts valorization, among others. These strategies are addressed and discussed throughout this review, as well as their recognized advantages and limitations. Overall, there is still a long way to go to attain the much-desired sustainability in the coffee chain, being essential to join the efforts of all actors and entities directly or indirectly involved, namely, producers, retailers, roasters, governments, educational institutions (such as universities and scientific research institutes), and organizations.     

Influence of extraction temperature on the final quality of espresso coffee

The final quality of espresso coffee (EC) depends upon certain technical conditions, such as the extraction temperature used in preparing it. The aim of this work was to investigate the effects of water temperature (88, 92, 96 and 98 °C) on the final quality of three types of EC (Arabica, Robusta Natural blend and Robusta Torrefacto blend) in order to select the optimal temperature. Volatile compound (analysed by Static headspace gas chromatography/mass spectrometry) and sensory flavour profiles were the most relevant parameters, whereas physicochemical, taste and mouthfeel parameters were not very useful for selecting the water temperature. For Arabica and Robusta Natural blend ECs, 92 °C was the optimal water temperature. For Robusta Torrefacto blend EC the overall acceptability might lead to the selection of 88 °C as the ideal water temperature, but the high percentages of key odorants related to roasty and earthy/musty flavours and the ‘not hot enough’ perception dictated the selection of 92 °C in this case as well. © 2003 Society of Chemical Industry     

Influence of roasting and brew preparation on the ochratoxin A content in coffee infusion

A study of the effect of coffee processing in the ochratoxin A (OTA) level has been carried out from the green beans to the drinking form. The analysis of OTA has been carried out by an in-house validated HPLC method with fluorescence detection. The limits of detection were 0.04 µg/kg for green and roasted coffee, and 0.01 µg/L for coffee brew. Thirty-six green coffee samples of different origin (Colombia, Costa Rica, Brazil, Vietnam, India and Uganda) were analysed. The highest concentrations of OTA were found in Vietnamese samples - Robusta species treated by dry processing - (range 0.64-8.05 µg/kg), that also showed the highest percentage of defective beans (7.6%). These contaminated samples were roasted in a process that controlled loss of weight and color, as in the industry. A mean reduction of 66.5% was obtained, but the reduction seems to be heterogeneous. Coffee brew was prepared by the three brewing processes more utilized in Europe: moka, auto-drip and espresso. A reduction of the OTA level has been attained, being greater when using a espresso coffee maker (49.8%) than when using auto-drip (14.5%) or moka brewing (32.1%). Therefore, the method of coffee brew preparation plays a key role in the final OTA human exposure.     

Influence of coffee/water ratio on the final quality of espresso coffee

Espresso coffee is a polyphasic beverage in which the physico‐chemical and sensory characteristics obviously depend on both the selection of ground roasted coffee and the technical conditions of the percolation process. The aim of this work was to evaluate the influence of the coffee/water ratio on the physico‐chemical and sensory quality of espresso coffee. Furthermore, the influence of botanical varieties (Arabica and Robusta) and the type of roast (conventional and torrefacto) on the selection of coffee/water ratio was studied. The relationship between pH and the perception of acidity intensity is discussed in relation to the influence of the coffee/water ratio, type of coffee and roast. The optimisation of other technical parameters in previous studies seemed to minimise the influence of an increase in the coffee/water ratio on the extraction of soluble and solid compounds. In fact, only some sensory attributes, such as bitterness, astringency and burnt, acrid and earthy/musty flavours were proposed as relevant to the selection of 6.5 g 40 mL^?1 or 7.5 g 40 mL^?1 in conventional roasted coffees (Arabica 100% and Robusta blend), and 6.5 g 40 mL^?1 in torrefacto roasted coffees. On the other hand, the addition of sugar during the roasting process in torrefacto roast coffees seemed to contribute to a higher generation of acids, melanoidins and other compounds by the Maillard reaction or caramelisation, which led us to select the lowest coffee/water ratio. Copyright © 2006 Society of Chemical Industry     

Sediments in coffee extracts: Composition and control by enzymatic hydrolysis

The water-insolubility of some coffee extract components is one of the major limitations in the production of instant coffee. In this work, fractions from coffee extracts and sediments were prepared, and their chemical composition determined. Based on the carbohydrate analysis, galactomannan was found to be the main polysaccharide component of the insoluble fractions and probably responsible for sediment formation. The suitability of twelve commercial enzymes for the hydrolysis of the insoluble fractions was investigated. Pectinase 444L was the most effective enzyme in releasing sugars, mainly mannose and galactose, from these substrates. Biopectinase CCM, Rohapect B1L, Pectinase 444L and Galactomannanase ACH were found to be the most effective enzymes for reducing the sediment of coffee extracts. The highest sediment reduction was obtained using Rohapect B1L and Galactomannanase ACH, at enzyme concentrations of 0.3 and 0.1 mg protein/g substrate, respectively.     

咖啡油香气成分的初步分析

采用水蒸气蒸馏法和柱色谱法对咖啡油样品进行预处理,然后,用GC/MS联用仪对咖啡油中的挥发性香气成分进行分离、鉴定。     

Method development and validation for isoflavones quantification in coffee

This paper reports the development and validation of an analytical method to quantify three isoflavones (daidzein, genistein and formononetin) in coffee beans and coffee brews, by HPLC with diode-array detection. The aglycones were released by methanolic acid hydrolysis in the presence of the antioxidant BHT and the internal standard 2′-methoxyflavone. The method showed high correlation coefficients (r > 0.999) for standards subjected to the entire procedure. For samples, good intra- and inter-day precisions (<8%), and accuracies (recoveries of 95 ± 1% for ground coffee and 92 ± 2% for coffee brew) were achieved. Detection and quantification limits ranged from 5 to 8 ng/mL and from 14 and 25 ng/mL, respectively. The proposed method proved to be sensitive, precise and accurate.     

Characterization of Turkish-Style Boiled Coffee Aroma by Gas Chromatography and Mass Spectrometry and Descriptive Analysis Techniques

The characteristic volatiles of light, medium, and dark roasted Turkish-style boiled coffee brews were studied by headspace solid-phase micro extraction/gas chromatography-mass spectrometry and sensory flavor profile analysis. Sixty-five volatile compounds, including furans, pyrazines, pyrroles, phenols, pyridines, ketones, oximes, alcohols, aldehydes, thiophenes, benzenes, and terpenes, were isolated from Turkish-style boiled coffee samples. The flavor profile analysis showed Turkish coffee brews as roasted/burnt, spicy, bitter, acidic, sweet, salty, astringent (dry), woody, fermented, earthy, and tobacco-like flavor characteristics. It was concluded that Turkish coffee was rich in furans, pyrazines, pyrroles, and phenols giving its roasted/burnt, spicy, woody, and fermented flavor characteristics.