促干剂处理对无核白葡萄干香气的影响

为探究促干剂的使用对无核白葡萄干的香气产生的影响,本研究利用顶空固相微萃取气相色谱质谱联用技术,对经过促干剂处理的无核白葡萄干样品的香气成分进行分析,结果表明在检测到的43种主要的葡萄干香气中,对葡萄干风味有贡献的有12种物质:己醛、2-己烯醛、（E）-2-庚烯醛、壬醛、苯乙醛、己酸乙酯、2-戊基呋喃、1-辛烯-3-醇、2,6-二乙基吡嗪、里那醇、大马士酮、香叶醇。研究表明促干剂处理对葡萄干主要香气物质种类无显著影响,但对不同香气物质的量上有一定影响:促干剂处理的无核白葡萄干中呈花香、果香、青香和蔬菜香的酸类、醇类、醛类等物质含量较高,而呈烘烤味的吡嗪类等物质含量较低。      

Raisin processing: physicochemical,nutritional and microbiological quality characteristics as affected by drying process

Processing and conservation of grapes by suitable techniques has been a major challenging issue for a long time. Optimization of drying and pretreatment operations of this fruit have been extensively studied. However, in order to achieve the production of high-quality raisins and reach consumers’ acceptance, special attention for quality attributes should be taken into account. Quality characteristics of grapes such as color, texture, vitamins, phytochemicals, aroma profile and microbial stability are of paramount importance since they could vary throughout the dehydration procedure and would directly determine quality perception and consumer choice. This paper presents a comprehensive review of the physicochemical, nutritional and microbiological characteristics of dried grapes as affected by the drying process. In addition, it investigates the changes of different grapes quality attributes (mainly nutritional and aromatic proprieties) during processing, which enables professionals and scientists to better choose and optimize grape processing to deliver the highest raisin quality to consumers.     

Detection of 2,4,6-trichloroanisole in microorganism-free irradiated raisins by solid-phase microextraction and GC-MS

The occurrence of 2,4,6-trichloroanisole (TCA) in nonprocessed dry-on-the-vine (DOV) and Thompson seedless irradiated raisins extracted by solvent-free solid-phase microextraction (SPME) was confirmed using gas chromatography/mass spectrometry. The 42 kGy (kilo Gray) dose irradiated DOV and Thompson seedless raisins incubated in five growth media were shown to be free of microorganisms. The quantity of TCA in the irradiated raisins was 0.39±0.05 ng/kg compared with 0.56±0.17 ng/kg in nonirradiated samples. The observation supports the view that raisins biosynthesize a minute but detectable quantity of TCA. The SPME fiber (divinylbenzene/carboxen/polydimethylsiloxane) method was simpler and quicker than the Likens-Nickerson extraction method for TCA determination. The biochemical mechanism of TCA production in raisin grape is unknown, but information in the biochemical literature of abundant phenolic substrates in grape berry, the presence of methyltransferases in Vitis tissues and of a chlorinating system provides a plausible basis for further investigation of the process.     

Microwave Drying of Grapes in a Single Mode Cavity at 2450 Mhz - 11: Quality and Energy Aspects

ABSTRACT

Drying studies were conducted to optimize process parameters (air temperature T. microwave power density P and air velocity u) for quality and energy in microwave drying of grapes using a single mode cavity applicator at 2450 MHz. Thc quality was assessed by several attributes like colour. damage, darkness, crystallized sugar, stickiness and non-uniformity. Colour and damage attributes provided more preeise predietability when compared to the other quality attributes. Microwave dried raisins were lighter in colour and hence were superior to hot air dried samples. Quality attributes were sipnificantlv dependent on T. P and u. Increase in air velocitv resulted in better Quality raisins where as P and T had the opposite effect. Optimum selection of T, P and u was found to be critical to achieve an energy efficient process for a quality product. Response surface models in terms of temperature m d micowave power were obtained for each of the quality attributes. Process optimization of the operating variables through response surface method was performed by imposing certain constraint levels on quality attributes     

Use of an oxygen absorber for disinfestation of consumer packages of dried vine fruit and its effect on fruit colour

The mortality of three life cycle stages of red flour beetle (Tribolium castaneum (Herbst)) was assessed in sealed 500 g packs of golden-coloured, sultana raisins, with or without the addition of a commercial O₂ absorber, Ageless^®. Assessments were undertaken at 30°C for 9 days, or 22.5°C for 20 days, or 15°C for 45 days. All fruit samples treated with O₂ absorbers produced 100% mortality, with no occurrence of a second-generation population, when incubated post-treatment at 27°C for 60 days. Fruit stored in an hermetically sealed bag produced 100% adult mortality at 22.5°C and 30°C but eggs and pupae survived; at 15°C mortality was not significantly different to the control culture. The effect of a low O₂ atmosphere generated by Ageless^® on fruit colour was assessed using the same temperature regimes over a 28, or 56, or 84-day storage period. Fruit colour changes were measured using the CIE tristimulus L^*, a^*, b^* measuring system. Low storage temperature (15°C) and low O₂ atmosphere both maintained fruit colour during the experimental storage regimes. There were significant negative effects on fruit colour at the higher temperature (30°C) and longer storage period without a modified atmosphere.     

微波预处理对无核白葡萄自然干制影响的研究

葡萄自然干制需要大约三至四周的时间，不同地区不同季节干制时间的长短还有差别。化学促干剂的处理可以大大缩短干制周期。如果将化学促干剂与微波处理相结合，然后再将葡萄进一步进行自然干制，可以进一步将葡萄干制速度提高近两倍。     

Near Infrared Analysis Potential for Grading Raisin Quality and Moisture

Near infrared transmittance (NIT) spectroscopy was examined as a means for measuring raisin quality. High positive correlation was found between measured values and those predicted by NIT for bulk density, visual grade, and moisture content. NIT measures properties at the molecular level. Thus, results showed a relationship between raisin quality and some chemical constituents. NIT analysis has the potential for measuring general raisin quality as well as specific constituents.     

Improving grape quality using microwave vacuum drying associated with temperature control

ABSTRACT:  Microwave (MW) vacuum dehydration using temperature to control the level of MW power demonstrated potential in improving the performance of the process. Product surface temperature measured by an infrared temperature sensor was used to control MW power at any level between 0 and 3 kW. Multiple linear regression analysis indicated an r ²= 0.942 for prediction of final moisture content and r ²= 0.985 for prediction of puffed character of grapes based on product temperature, time, specific energy, fresh fruit sugar, and fresh fruit moisture content. Temperature was found to be the most significant predictor. The elemental and compound contents of grapes dried using MW vacuum was compared to sun-dried raisins. The grapes dried using MW vacuum exhibited better preservation. Vitamin A was found in the MW-vacuum-dried grapes but none was detected in the raisins, and Vitamin C, thiamine, and riboflavin were also higher in the MW-vacuum-dried grapes than in the raisins.     

Mycotoxins in botanicals and dried fruits: A review

Botanicals are used in many countries for medicinal and general health-promoting purposes. Numerous natural occurrences of mycotoxins in botanicals and dried fruits have been reported. Aflatoxins or ochratoxin A (OTA) have been found in botanicals such as ginseng, ginger, liquorice, turmeric, and kava-kava in the USA, Spain, Argentina, India, and some other countries, while fumonisins have been found in medicinal wild plants in South Africa and in herbal tea and medicinal plants in Turkey. Zearalenone was identified in ginseng root. Dried fruits can be contaminated with aflatoxins, OTA, kojic acid, and, occasionally, with patulin or zearalenone. One main area of concern is aflatoxins in dried figs; bright greenish yellow fluorescence under ultraviolet light is associated with aflatoxin contamination. OTA in dried vine fruits (raisins, sultanas, and currants) is another concern. There are also reports of aflatoxins in raisins and OTA in dried figs, apricots, dried plums (prunes), dates, and quince. Maximum permitted levels in the European Union include 4 µg kg^-1 for total aflatoxins in dried fruit intended for direct consumption and 10 µg kg^-1 for OTA in dried vine fruit. This review discusses the occurrence of mycotoxins in botanicals and dried fruits and analytical issues such as sampling, sample preparation, and methods for analysis. Fungal contamination of these products, the influence of sorting, storage, and processing, and prevention are also considered.