Storage Conditions Affect Quality of Raisins

Raisins had a moisture content of ca 14% and were stored over an 11 mo period. The initial SO₂ content was ca 640 ppm. Moisture content, water activity, color, browning, texture, SO₂ content, soluble sugars, acidity and pH were periodically determined. A substantial decrease in SO₂ content was observed, especially in samples stored at room temperature (20–25°C) which had higher browning indexes. No substantial changes were detected in water activity, acidity and pH. No sugaring was observed. Refrigerated samples (stored at 4 and 11°C) were of higher quality in comparison with nonrefrigerated samples. Both were suitable for consumption after storage.     

In Vitro Iron Bioavailability and Antioxidant Activity of Raisins

ABSTRACT: Iron bioavailabilities and antioxidant activities of 3 generic raisin types-Golden Thompson, Dipped Thompson, and Sun-dried Thompson-were quantified and compared. Iron bioavailability was assessed with an in vitro digestion/Caco-2 cell culture model using cell ferritin formation as an index of iron bioavailability. Antioxidant activity was determined using the total oxyradical-scavenging capacity (TOSC) assay. Ferritin formation in Caco-2 cells was low for all 3 raisin types, indicating low iron bioavailability. Ethylenediaminetetraacetic acid (EDTA) enhanced iron bioavailability from raisins but ascorbic, citric, and tartaric acids showed no effect. Antioxidant activity was significantly higher in Golden Thompson than Dipped Thompson and Sun-dried Thompson, suggesting that enzymatic browning negatively affected antioxidant activity.     

响应面法优化超声波辅助清洗无核绿葡萄干工艺

针对葡萄干加工企业清洗无核绿葡萄干后无核绿葡萄干极易褐变的问题,采用超声波辅助清洗工艺,在单因素实验基础上,选择清洗剂酒精度、清洗温度和清洗时间为影响因子,褐变指数BI值为指标,通过响应曲面法设计和分析,最佳清洗条件下清洗的葡萄干用热泵干燥。实验表明无核绿葡萄干超声波辅助清洗工艺的最佳条件:清洗剂酒精度44%vol、清洗温度9 ℃、清洗时间90 s,在此条件下,无核绿葡萄干BI值仅为33.43,较传统自来水喷淋清洗降低26.98%。热泵干燥葡萄干的最佳温度是50 ℃,无核绿葡萄干BI值仅为23.69,略低于未清洗无核绿葡萄干,较相同温度下热风干燥降低28.52%。     

响应面法优化葡萄干天然酵母面包的配方

目的：为了优化葡萄干天然酵母面包的配方。方法：在单因素实验的基础上,选择葡萄干天然酵母液添加量、白砂糖添加量、黄油添加量为影响因素,感官评分为响应值,采用Box-Behnken试验设计方法,对面包配方进行优化,并对其理化和微生物指标进行测定。结果：葡萄干天然酵母面包的最佳工艺配方为：葡萄干天然酵母液添加量12%、白砂糖添加量18%、黄油添加量9%,改良剂添加量0.3%,此条件下面包产品感官评分为86,与理论预测值相比,其相对误差约为2.38%。在此条件下制得的面包的理化和微生物指标如下：水分含量30%,酸度5.1 °T,比容5.8 mL/g,菌落总数201 CFU/g,大肠菌群0,霉菌计数2 CFU/g,致病菌未检出。结论：优化的面包配方条件合理,葡萄干天然酵母面包具有较好的品质。     

SOLAR DRYING OF GRAPES

Mass losses and low quality are the most serious disadvantages of traditional grape drying methods. For the production of high quality raisins an increase in the drying rate is required and the grapes should be protected from rain, dust and insects during drying.

Under the terms of a joint German-Greek research program low-cost solar grape dryers were developed in the Institute of Agricultural Engineering of Hohenheim University and were tested in Greece in cooperation with the Crete Agricultural Research Center.

The required data basis for optimizing solar grape dryers was obtained by additional laboratory tests measuring the influence of various drying parameters on drying rate and quality.

Tests with the solar dryers have shown that it is possible to reduce the drying time and improve the quality significantly compared to the traditional drying methods. Also mass losses due to rain can be prevented.     

Microwave Pre-treatment for Sun-Dried Raisins

Commercial sun-drying of raisins requires a long time, and chemical pretreatments are used to increase the drying rate. The feasibility of improving the sun-drying process of grapes by microwaves was investigated. Sultana seedless grapes, dipped in alkali solution, were pre-treated in a domestic microwave oven and dried by direct solar radiation. Microwave pre treatment reduced the moisture content by 10–20%. The microwave-treated grapes dried nearly two times faster than the controls. Blanching in boiling water had the same effect on the drying rate as microwaves. Color and appearance of treated grapes were comparable to commercial products.     

Aflatoxins and ochratoxin A in export quality raisins collected from different areas of Pakistan

During 2012–2014, 170 samples of export quality raisins were collected from different vendors in Pakistan. The collected samples were analysed for the presence of aflatoxins (AFs) and Ochratoxin A (OTA) contamination using high-performance liquid chromatography technique. The limit of detection and limit of quantification of AFs/OTA were 0.12/0.10 and 0.36/0.30 µg kg^?1, respectively. Only 5% of the samples were contaminated with AFs, ranging 0.15–2.58 µg kg^?1 with a mean of 0.05 ± 0.26 µg kg^?1. None of the raisin samples exhibited AFs contamination above the maximum limit (ML = 4 µg kg^?1) as set by the European Union (EU). About 72% of the samples were contaminated with OTA, ranging 0.14–12.75 µg kg^?1 with a mean of 2.10 ± 1.9 µg kg^?1. However, in 95.3% of the tested samples, OTA level was lower than the ML of 10 µg kg^?1 as regulated by the EU. Apparently, a strict and continuous monitoring plan, including regulatory limits, improves food safety and quality for all types of commodities.     

SOLAR TUNNEL DRYER WITH INTEGRATED COLLECTOR

A solar tunnel dryer with integrated collector was developed and tested. This low-cost system can be produced either by small scale industries or farmers themselves using simple tools and relatively cheap materials. Depending on weather conditions about 1000 kg grapes can be dried within 4 to 7 days. According to the drying capacity the solar drying system can be successfully applied to farms with an acreage of 0.5 to 1.0 hectare.

Compared to traditional sun drying methods solar drying reduces significantly drying time and mass losses. During drying the crop is completely protected from rain, dust, animals and insects and doesnâ¢? come into contact with foreign materials.     

用于面包制作的葡萄天然酵母发酵工艺优化

以葡萄干为发酵原料,研究不同发酵工艺参数对葡萄天然酵母发酵力的影响,为用于面包中的天然酵母发酵优化工艺提供一定的试验数据。以单因素试验为基础,采用响应面分析法对发酵工艺参数进行优化,结果表明:最优发酵条件为培养温度26℃,培养时间4d,葡萄干与白砂糖配比101。该条件下,天然酵母发酵力为0.077 9,与市售的即发干酵母的发酵力较为接近,可代替其用于面包的制作中。