2种浓缩方法对柠檬汁特性影响的比较

采用界面渐进冷冻浓缩法和真空蒸发法分别对柠檬汁进行界面渐进冷冻浓缩和真空蒸发浓缩。通过对 2种浓缩液处理前后柠檬汁香气成分含量的定性定量分析 ,以及柠檬汁色差、Vc含量、电导和 pH值的比较分析 ,证明了冷冻浓缩柠檬汁明显地比真空蒸发浓缩果汁能更好地保持柠檬汁的香气成分、Vc含量和原汁的香气协调性。     

果蔬汁常压低温浓缩新技术—界面渐进冷冻浓缩

冷冻浓缩是将天然果蔬汁中的部分水阈结成冰并将其分离去除,以得到高品质的浓缩汁或成品果蔬汁的收缩方法。界面渐进冷冻浓缩法与传统的悬浮结晶冷冻浓缩技术相比,是一种投资少,成本及能耗低的冷冻浓缩新技术,适合于果蔬汁浓缩工序采用。天然番茄汁通过界面渐进冻结可浓缩至40．8％。对浓缩汁稀释还原后的测试结果表明,除离子浓度外,酸度,维生系C及色度等与原汁相比几乎无可见差异。     

纳滤浓缩西番莲果汁的研究

根据西番莲原汁中的有机物组成及分子量,选择合适的纳滤膜对西番莲澄清果汁的浓缩过程进行研究.通过系统考察影响膜通量的因素,发现适当提高温度、压力可以提高膜通量.在不破坏西番莲果汁中的芳香成分及Vc等营养成分和不超过膜的压力操作范围的前提下,得到较适的操作温度和压力.选择在操作温度为28 ℃左右,压力为3 MPa时,分离效果最好,此时实际膜通量达17 L/(m2.h).经过纳滤浓缩,西番莲澄清汁可溶性固形物从13oBx提升到30oBx左右.本实验可以达到较好的膜通量和截留率,为在工业化浓缩西番莲澄清汁过程中,利用膜技术大大减少芳香成分及Vc等营养成分损失提供参考.     

不同冷冻浓缩度对和田红葡萄酒品质影响

主要研究不同冷冻浓缩度对和田红葡萄汁发酵酒的常规理化指标、生物活性指标的影响,并结合感官评价研究最佳浓缩度。以可溶性固形物值为浓缩度,对经冷冻浓缩处理浓缩度为27%、31%、35%、39%、43%的和田红葡萄汁为原料发酵为不同浓缩度和田红葡萄酒,以未经冷冻浓缩处理的和田红葡萄酒为对照进行分析。结果表明:浓缩度为31%的葡萄酒总酚、单宁、黄酮含量分别为0.74、0.84、1.10 g/L,且增幅最大,较浓缩度27%时分别提高了18.78%、16.86%和20.08%。综合感官评分为4.56,酒体较平衡、协调性较好,整体品质较高。因此利用冷冻浓缩的葡萄汁发酵,可以明显提高葡萄酒品质。     

雪莲果浓缩清汁的澄清工艺研究

研究雪莲果浓缩清汁的澄清工艺.以透光率、蛋白质含量、总糖、还原糖及糖类成分组成等为指标,比较醇法、壳聚糖絮凝法、超滤3种方法对雪莲果浓缩汁的澄清效果.结果表明,3种澄清方法得到的浓缩汁澄清度均＞80%,用壳聚糖处理的浓缩汁放置后会出现少量混浊;浓缩汁多酚含量是醇法＞壳聚糖絮凝＞超滤;蛋白质含量从84.65 μg/mL降至20μg/mL以下,其中超滤去除蛋白质能力最强,含量仅为4.27μg/mL;醇法对还原糖有较大影响,总糖含量是醇法＞超滤＞壳聚糖絮凝.     

冷冻浓缩处理对荔枝汁品质的影响

为了研究冷冻浓缩处理对荔枝果汁品质的影响,采用华南理工大学自主研制的冷冻浓缩处理装置,将荔枝原汁经过多级浓缩得到不同可溶性固形物含量的浓缩汁,复原后测定其理化特性及营养成分,包括pH 值、总酸、还原糖、蛋白质、VC 等指标。结果表明：随着浓缩级数的增加荔枝汁浓度不断提高,3 级浓缩汁可溶性固形物含量达45.3°Brix;复原后pH 值、总酸、还原糖和蛋白质没有显著的变化,VC 含量略有下降,保留率为85%,远远小于热处理损失。冷冻浓缩处理对荔枝汁有很好的浓缩效果,并且能很好地保存荔枝汁原有的营养物质,是一种很有前景的冷加工技术。     

膜法酵母提取海藻糖应用初探

采用超滤 纳滤技术对活性干酵母溶液中的海藻糖进行提取研究 ,结果表明 :MWCO为 5 0 0 0的卷式超滤膜可截留约 98%以上的蛋白质 ,起到纳滤预处理的作用 ;MWCO为 30 0的卷式纳滤膜对超滤液进行纳滤预浓缩和渗滤操作 ,发现浓缩过程通量随压力的增加而增加 ,随浓缩时间的延长而迅速下降 ,海藻糖截留率变化不大 ;渗滤过程表明渗透通量随渗滤时间的延长而略有增加 ,海藻糖截留率变化不大。经过超滤 纳滤处理 ,海藻糖提取率达 85 %以上 ,纯度 99.4 % ,优于传统乙醇提取方法     

膜分离技术在菠萝汁加工中的应用研究

采用膜分离技术,包括超滤、反渗透、纳滤,分别对菠萝汁进行处理,研究了各种膜的运行时间与操作压力对膜分离效果的影响,并对膜分离效果进行评价.结果表明,超滤处理菠萝汁的最佳操作压力为0.12MPa,反渗透与纳滤处理菠萝汁的最佳操作压力均为0.50MPa.卷式膜的抗污染能力优于中空纤维式膜,碱液清洗后卷式膜的膜通量恢复率达到了96%以上;超滤膜分离可基本保留菠萝汁中的营养成分,并有效去除果汁中的微小颗粒物质.起到了澄清作用;反渗透与纳滤处理菠萝汁,能够对果汁起到一定的浓缩作用.     

菠萝原汁真空微波浓缩前后挥发性成分变化研究

菠萝浓缩汁是菠萝最主要的加工产品,在常规的加热浓缩过程中通常伴随着易挥发的香气成分损失.为了探明最容易挥发损失的香气成分,同时建立一种鉴别菠萝汁饮料是由鲜榨菠萝汁还是由菠萝浓缩还原汁生产的方法,进行了菠萝原汁的真空微波快速浓缩前后挥发性成分的变化规律研究.采用顶空固相微萃取-气质联用方法对菠萝原汁和菠萝真空微波浓缩还原...     

沙棘原汁澄清处理对沙棘酒香气成分的影响

为研究沙棘原汁澄清处理对沙棘酒发酵速度和香气成分形成的影响,利用果胶酶对沙棘原汁进行澄清处理。分别对沙棘澄清汁和未处理的沙棘原汁调整到糖度23%、pH3.7,然后接入0.18%的活性干酵母于28.5℃下发酵,陈酿后采用气-质联用仪(GC-MS)对各发酵酒进行香气成分检测。结果表明:以澄清汁为原料发酵的沙棘酒中检测出58种香气化合物;原汁发酵的沙棘酒中检测出52种香气成分,其中有28种非两者共有,产生了非常明显的香气差异。主要香气成分为3-甲基-1-丁醇和辛酸乙酯,用澄清汁发酵的沙棘酒其相对含量分别为31.24%和10.40%,较原汁发酵的沙棘酒分别提高了16.45%和5.32%。因此表明对沙棘汁澄清处理更有利于沙棘酒香气的形成。     

QUALITY CHANGES DURING STORAGE IN KOREAN CLEAR PEAR JUICES CONCENTRATED BY THREE METHODS

Pears of Shingo variety were coarsely ground, and subjected to heat treatment by HTST (high temperature short time) and pectinase treatment to produce a cloudy pear juice. The pear juice was then treated with Viscozyme, gelatin and bentonite, and filtered through an ultrafiltration membrane to produce a clear pear juice. The clear pear juice was concentrated to 3 to 5 fold by vacuum evaporation, freeze concentration, and reverse osmosis methods. The concentrates were diluted to 10° Brix and stored at 4C for 15 days. The single strength juice was evaluated for color, turbidity, heat stability, and sensory preference at 5 day intervals during storage. The pear juice concentrated by the three methods showed only small differences in quality. While the clear pear juice with added ascorbic acid had no quality changes at 4C after 15 days' storage, that without the addition of ascorbic acid resulted in some deterioration in browning, turbidity and heat stability after 10 days' storage. There were small, but significant flavor differences among clear pear juices concentrated by evaporation, freeze concentration and reverse osmosis.     

Flavor Losses in Orange Juice during Ultrafiltration and Subsequent Evaporation

Losses of volatile compounds in orange juice during ultrafiltration and subsequent evaporation were studied. Alcohols and esters predominated in the permeate, while terpenes (d-limonene and valencene) and nonpolar aldehydes (octanal and decanal) were distributed in the retentate from the ultrafiltration (UF) system. Fractions of some flavor compounds were lost during ultrafiltration process. An aqueous phase essence was recovered from the permeate during evaporative concentration. No oil phase was observed. When whole juice was concentrated, both oil and aqueous phases were recovered. Essence recovery efficiency of individual compounds was 3 to 13% when concentrating permeate and <5% when concentrating whole juice.     

Evaluation of hybrid pressure-driven and osmotically-driven membrane process for non-thermal production of apple juice concentrate

This study investigates the potential of hybrid membrane processes including microfiltration (MF), ultrafiltration (UF) and forward osmosis (FO) for non-thermal concentration of apple juice. The process performance and characteristics (physicochemical properties, nutritional and aroma components and microbiological quality) of apple juice were studied. The clarity of apple juice was significantly promoted as pore size of membrane reduced. MF and UF can also ensure microbiological safety in pre-treated apple juice. According to its efficiency of filtration as well as performance of simultaneous clarification and cold-sterilization, 0.22 μm MF membrane was identified as the optimal membrane for the pre-treatment. The pre-treated apple juice can be concentrated up to 65°Brix by subsequent single stage FO. FO retained nutritional and volatile compounds of apple juice while significant reductions were found in the juice concentrated by vacuum evaporation. Hybrid MF-FO can be a promising non-thermal technology to produce apple juice concentrate with high quality.     

Quality of Freeze Concentrated Orange Juice

Pasteurized Valencia and Temple orange juices concentrated to 45°Brix by freeze concentration retained their fresh juice flavor. Direct steam infusion heating to inactivate enzymes allowed more rapid heating than indirect heating and successfully lowered juice peel oil during vacuum cooling. Except for considerable pulp reduction of feedstream juices, there were few differences from normal citrus juice recovery procedures for freeze concentration. Since the product retained most of the aroma constituents of fresh juice, careful handling and high quality feed juice prior to freeze concentration was much more important than for evaporation. Fresh juice freeze concentrated to 45°B, then pasteurized at temperatures of 80°, 97° and 111°C had reduced sucrose (up to 25%) as the temperature increased to 111°C.     

固相微萃取GC-MS法测定不同干燥方式下枣产品的芳香成分

采用顶空固相微萃取与气相色谱-质谱联用技术对枣鲜样及不同干燥方式枣产品的芳香成分进行分析.结果表明,河北滩枣鲜样主要芳香成分为:酸类物质占24.31%,烯类物质占14.2%,烷烃类物质占11.73%.热风干燥处理后产生较多酯类和酮类物质,使产品呈现蒸煮味道,损失较多烷烃类物质;微波干燥处理后除酯类和酮类物质增多外,其余...     

Coupling nanofiltration and osmotic evaporation for the recovery of a natural flavouring concentrate from shrimp cooking juice

A new combination of membrane-based processes was studied in order to produce a natural flavouring concentrate from shrimp cooking juice. The process associates a pre-concentration step by nanofiltration (NF) until a Volume Reduction Ratio (VRR) of 10 and a final concentration by osmotic evaporation (OE). Thanks to NF, the juice was partially concentrated and desalinated, allowing the further OE step to be run in optimal conditions: reduction of the quantity of water to be evaporated and of the production of brine, limitation of the loss of volatile compounds and improvement of sensory acceptability. During OE step run at pilot-scale, a 52% dry matter concentrate was obtained with aroma loss lower than 35%. Products were characterised by sensory and chemical analyses all along the process. With sensorial characteristics matching the expectancies, the concentrate could be incorporated at 2.5% in food preparations.     

低温油炸与冷冻干燥生产草菇脆片的特性

为研究真空低温油炸草菇脆片和真空冷冻干燥草菇脆片的品质特征,采用化学方法和气相色谱-质谱联用技术对新鲜草菇和2种草菇脆片的感官品质、水分、脂肪、粗蛋白和粗多糖等营养成分以及挥发性风味成分进行检测分析。结果表明,真空冷冻干燥草菇脆片内部组织孔径大,其硬度和脆度分别为5.965 kg和1.881 mm,脆片的颜色和营养成分含量与新鲜草菇接近;真空低温油炸草菇脆片内部结构疏松,硬度和脆度分别为4.454 kg和3.336 mm,其呈现出油炸食品特有的色泽,与新鲜草菇相比,脆片中的主要营养成分含量显著降低。此外,2种草菇脆片中挥发性风味物质的种类和数量与新鲜草菇相比都存在很大差异。新鲜草菇、真空低温油炸草菇脆片和真空冷冻干燥草菇脆片中检测出的总挥发性风味物质种类分别为27、16种和29种。新鲜草菇中主要的挥发性化合物为醛类(54.0%)、酮类(40.27%)和醇类(4.1%),其主要呈现出清香、花香和蘑菇风味;真空低温油炸草菇脆片中主要的挥发性化合物为烷烃类(79.83%)、含氮、硫化合物类(12.12%)及酮类(6.6%),主要呈现出焦香和烤香风味;真空冷冻干燥草菇脆片中主要挥发性化合物为烷烃类(81.07%)、酯类(8.54%)和含氮、硫化合物类(7.9%),其呈现的主要是果香味辅以烤香风味,因真空冷冻干燥草菇脆片中含有较多的挥发性化合物使其整体风味更丰富多样。     

喷雾干燥和真空冷冻干燥对百香果挥发性成分的影响

为了明确加工工艺对百香果挥发性成分的影响,以紫果百香果为原料,运用顶空固相微萃取-气相色谱-质谱联用技术(Solid-phase microextraction(SPME)and gas chromatography-mass spectrometry(GC-MS)研究了喷雾干燥和真空冷冻干燥对百香果挥发性成分的影响。结果显示,鲜汁、喷雾干燥果粉和真空冷冻干燥果粉中占主导的挥发性成分的种类和含量差异较大。鲜汁中主要的挥发性成分是酯类化合物,占总挥发性成分的89.39%。喷雾干燥果粉占主导的挥发性成分是醇类(34.38%)、酮类(20.50%)、胺类(21.69%)和烯类(13.21%),酯类化合物仅占总化合物的9.16%。真空冷冻干燥果粉中主要的挥发性成分是酯类,占共挥发性成分的42.49%。喷雾干燥后的果粉产生了更多的风味物质。真空冷冻干燥后的果粉,基本能够保持百香果原有的风味,为后续百香果干燥工艺的改进及其深度开发和合理利用提供了更多的科学理论基础。     

不同干燥方式的豆渣香气成分的顶空固相微萃取-气相色谱-质谱分析

采用顶空固相微萃取-气相色谱-质谱法研究干燥处理(晾晒、热风、微波、真空及真空冷冻干燥)对豆渣香气成分的影响,并结合香气阈值和相对气味活度值分析不同干燥豆渣的主体豆腥味成分。共检出52种挥发性成分,主要为醛、酮、醇、酯类等。晾干豆渣主要香气成分为3-羟基-2-丁酮(18.29%)、己醛(16.30%)和丙酮(11.87%),豆腥味成分最多且相对含量最高;热风干燥豆渣各挥发性组分相对含量均较低;微波干燥豆渣醇及酮类相对含量较高;真空干燥豆渣主要香气成分为苯甲醛(11.18%)和2,3-丁二酮(11.27%),产生仅少于晾干豆渣的豆腥味成分;真空冻干豆渣主要香气成分为乙酸乙酯(46.72%)和丙酮(22.86%),豆腥味成分仅占1.81%。