食品科学与工程外文参考文献译文及原文

本科毕业设计（论文）外文参考文献译文及原文
学院轻工化工学院
专业食品科学与工程
年级班别2006级（2）班
学号3106002145
学生姓名龚张卫
指导教师姜燕
2010 年 6 月
目录
1. 介绍 (1)
2. 材料与方法 (1)
2.1 原料 (2)
2.1.1市售猕猴桃果酱/果酱 (2)
2.1.2水果............................................................ .......... (2)
2.1.3渗透溶液............................................. (2)
2.1.4胶凝剂 (3)
2.1.5酸度调节剂 (3)
2.2猕猴桃果酱/橙果酱详细制作过程 (3)
2.2.1传统制作过程 (3)
2.2.2渗透失水水果制作过程 (3)
2.3分析 (3)
2.3.1理化性质 (3)
2.3.2 色泽测量......... ...... ...... ...................... . ...... . (3)
2.3.3 流动性能......................................... ... ............................ . (4)
3. 结果和讨论 (4)
结论 (9)
参考资料 (9)
渗透脱水水果制作果酱的研究
E. García-Martínez, G. Ruiz-Diaz, J. Martínez-Monzó, M. M. Camacho, N.
Martínez-Navarrete and A. Chiralt
瓦伦西亚大学食品技术系，巴伦西亚，46071
摘要：果酱是由水果和糖按比例混合制得的产品，最终产品含有最小30％果肉成分和最低45糖度值。

传统果酱制作需要通过热处理来浓缩加工，从改变感官和营养特性提高产品质量，营养特性的改变主要是果酱中抗坏血酸损耗量的多少。

另外一种浓缩方法是采用预先脱水的水果为制作果酱的原料，从而避免热处理这一过程。

用糖溶液进行渗透脱水处理被公认为避免果实品质发生较大变化的合适方法。

另一方面，渗透处理后渗透液中水溶性果肉成分变得丰富。

在这个过程中，用渗透液和渗透脱水处理后的水果混合生产猕猴桃果酱、橙果酱产品，生产过程没有对产品进行热处理加工，制作完成后对产品进行了分析研究。

分析配制产品的物理性质（外观色泽和流动性能）和理化性质（水分活度，糖度值，水分含量，pH值，酸度），并与市售果酱相关性质进行了分析比较。

关键词：果酱，橙果酱，渗透脱水处理，猕猴桃，橙子
1 介绍
正如西班牙国家标准规定（1974年）的下的定义，果酱是由最小40％（30%为柠檬）果肉成分和最低糖度值为45可溶性固形物组成的产品。

此外，诸如柠檬酸或胶凝剂，常用果胶等添加剂都可添加到果酱中作为其中成分。

在传统的果酱制作加工中，所有的原料按适当的比例进行混合并在常压或加压条件下对混合物进行热处理加工浓缩，以达到对果酱中可溶性物质含量的要求。

这个加工步骤能增稠果酱或增加其胶凝性，这样能确保水果酶被钝化并从水果中提取果胶和浓缩产品。

需要指出的是，加热过程中由于水果自我保护水果酸度和水分活度会降低。

果酱在烹煮制作过程中，当果酱温度达到一定时，它的色泽，质地，营养价值和风味上会发生不良改变。

另外一个制作方法是选择是采用预先脱水的水果为原料制作果酱，这就降低对浓缩步骤的要求。

在这个意义上，渗透脱水处理过程
使我们获得的果酱产品具有良好的风味，香气、营养成分和矿物质，更少维生素损失（迪克森;莱纳尔特和庞廷）。

在渗透脱水处理这个过程中，气温没有发生相对变化，水分能从水果转移到糖（通常是蔗糖）浓缩溶液中。

蔗糖溶液能防止水果发生非酶褐变和酶氧化褐变，从而使水果能保持新鲜，色泽更自然（庞廷;庞廷和石）。

此外，可适当加入添加剂来配制对水果进行脱水处理的渗透溶液（OS），这样和水果相混就能配制果酱。

通过这种方式，渗透脱水（OD）过程中水果中丧失的水溶性溶质可以恢复。

在这个认识上，新的果酱开发技术得到发展，其中渗透脱水水果和渗透溶液相混制作方法直接使用在草莓果酱加工制作中（Shi et al，1996）。

如果水果在较低温度（35-40°C）下短时间内进行渗透失水处理，制得的果酱产品就具有优异的天然色泽，美妙风味和较高的整体质量。

本文的目的是比较应用新生产方法制得的猕猴桃果酱、橘果酱和市售果酱产品间的物理和物理化学性质参数。

分析过程应特别注意观察果酱的色泽属性，因为这些性质特别容易受热处理加工的影响。

2 材料与方法
2.1 原料
2.1.1 市售猕猴桃果酱/橙果酱
在瓦伦西亚（西班牙）当地超市购买八份传统工艺生产的橙果酱样本（COM）和两份猕猴桃果酱样本（CTKJ和CDKJ），使用这些果酱进行研究。

由于没有找到更多的市售猕猴桃果酱，其中一份由果糖配制成营养果酱产品（CDKJ）。

2.1.2水果
在瓦伦西亚（西班牙）当地市场购买新鲜的橙（瓦伦西亚脐橙）和猕猴桃（中国品种猕猴桃）。

2.1.3 渗透溶液
渗透溶液由市售食品级蔗糖和微温的蒸馏水制成，制备时，渗透溶液要摇混直至蔗糖完全溶解，并且使渗透液糖度值为70（用于橙样本），另外一份糖度值为55（用于猕猴桃样本）。

每次试验中渗透溶液浓度的确定应根据前人对水果渗
透失水动力学研究和最终猕猴桃果酱/橙果酱产品的成分合乎法律和商业标准基础上。

2.1.4 胶凝剂
两种不同种类的胶凝剂的使用。

猕猴桃果酱生产采用高甲基果胶增稠（由Hercules公司提供），橙果酱制作采用NAP（由德国Hahn & Co提供的市售结凝胶和果胶的混合物）。

2.1.5 酸度调节剂
只在橙果酱中加入柠檬酸，使产品最终pH值为3.5-3.6。

2.2 猕猴桃果酱/橙果酱详细制作过程
使用预先渗透失水处理好的水果制作猕猴桃果酱，这样能够避免热处理步骤（ODKJ样本），用渗透失水处理的橙片制作橙果酱，同时用传统的方法制作传统果酱（TOM）。

2.2.1 传统制作过程
鲜橙切成的薄片与市售白糖，NAP，柠檬酸混合煮沸浓缩以获得可溶性固形物含量为56％的橙果酱。

2.2.2 渗透失水水果制作过程
样品被切成薄片（橙片厚0.5厘米，猕猴桃片厚1厘米），薄片分别放在一个含有相应渗透液的搅拌罐中，在30 °C条件下进行渗透失水处理一小时。

薄片完全浸泡在搅拌罐中溶液里。

在猕猴桃果酱/橙果酱生产过程中，用一定量的渗透溶液与胶凝剂、酸度调节剂相互混合，并加热渗透液到80℃，让凝胶剂、酸度调节剂切底溶解。

将渗透失水处理后的橙薄片和猕猴桃薄片分别在打浆机（Kenwood）中磨碎，然后各取适当比例与配制的渗透液相混合。

通过这种生产方式得到的产品称为渗透失水橙果酱（ODOM），渗透失水猕猴桃果酱(ODKJ).
所有猕猴桃果酱/橙果酱装进玻璃瓶并在冷藏条件下（6℃）储存直至被拿出来进行分析。

2.3 分析
2.3.1 理化性质
运用AOAC 20103 方法(1980)确定果酱中水分含量。

可溶性固形物含量在20°C下通过测量含糖量来确定（89553型阿贝折射仪）。

水分活度（aw）运用露点式湿度计（培安科技CX-2）来测定，ph值由克里松2001小型ph测量器确定，酸度（x克柠檬酸/100克果酱样本）通过滴定方法来确定。

以上测量方法请参照AOAC 942.15规则(1980).并且每一分析试验各做三次。

2.3.2 色泽测量
果酱褐色度由通过MinoltaCM-1000分光光度计测量一系列反射光谱确定。

首先确定相干红外能量L* a* b*的彩色坐标(D65, 10°)，测量时，果酱样品放置在一个烧杯中并用光学玻璃覆盖。

2.3.3 流动性能
两种不同的评估分析方法。

反挤压试验:在20 °C室温下将样本放置在面包型玻璃盒（直径6cm）里，然后样本放在XT2型物性测试仪（Stable Micro Systems 公司）直径为4.95 cm 柱塞内，并以1mm/ s挤压变形速率进行反挤压试验。

粘稠度测试：使用Bostwick稠度计测量在恒定时间可控重量样本流动的距离。

将一个平放的不锈钢槽分为两个隔间。

第一个隔间（5 × 5 × 3.8厘米）装有样品并用弹簧门与第二个隔间分开。

第二个隔间宽5厘米，长24厘米，高2.5厘米，底部画有一系列0.5厘米间隔的平行线。

当弹簧门被打开就开始计时，测量样品在30秒内流动的距离（Bourne，1982年）。

3 结果和讨论
表1展示了市售猕猴桃果酱/橙果酱出现在其产品标签上的成分，同时展示果酱成分间的物理化学相互作用结果。

我们能观察到不同种类市售猕猴桃和橙果酱产品的含糖量，水分含量和水分活度有很大范围不同。

对于市售猕猴桃产品，根据西班牙国家标准34-074-74，食用果酱糖度值不符合法律规定的最低值，CTKJ果酱样本糖度值则极大超出这一限制值。

市售橙
果酱产品糖度值应在49至66之间，但COM1 和COM7果酱样本标签上明确标出的果肉成分含量低于UNE的要求。

插图1展示水分活度值与糖度值相关性，插图是根据诺里什（1966年）在假定产品中唯一可溶性糖为蔗糖或者葡萄糖-果糖，预测产品水分活度值而绘制。

所有水分活度实验值介于两条预测线间，实验值与产品糖度值（不同比例的蔗糖，葡萄糖-果糖）相一致。

实验室得到的产品(ODKJ, TOM and ODOM)实验值取决蔗糖线，蔗糖线是根据产品制作配方中主要糖类组成画成的。

产品的水分活度越低或糖度值越高，产品稳定性越高。

表1 市售可食用猕猴桃果酱/橙果酱产品组成和测定的物理化学性质（平均值±标准差，
重复3次）
a CTKJ,市售传统猕猴桃果酱; CDKJ, 市售食用猕猴桃果酱; ODKJ, 渗透失水处理猕猴桃果酱; COM,
市售橙果酱; TOM, 传统橙果酱; ODOM, 渗透失水处理橙果酱. b xg水/100g样本 c xg柠檬酸/100g样本 d 75% 果糖糖浆. e 没有在标签上明确说明组成成分
插图1展示了配制猕猴桃果酱和橙果酱水分活度值与糖度值相关性，图中线条是在假设产品中唯一可溶性糖为蔗糖或葡萄糖-果糖条件下由预测值组成的(ODKJ, 渗透失水处理的猕猴桃果酱; TOM, 传统的橙果酱; ODOM,渗透失水处理的橙果酱).
考虑到市售果酱产品组成成分范围广泛，猕猴桃果酱/橙果酱配方原料可从这个范围选择并制作成产品，但同时要符合西班牙法律要求(UNE, 1974UNE (Una Norma Española). (1974). 34-074-74.UNE,1974)。

表2显示了在每种情况下可使用的原料和其组成成分。

可以看出ODKJ和ODOM样本中每100克最终产品分别含有37.8g和44.3g新鲜果肉。

由质量平衡确定渗透失水处理的水果和渗透溶液（主要是渗透失水处理橙果酱中的蔗糖）的比率相混合，OD水果和渗透溶液各有一部分构成果酱，能使ODKJ和ODOM果酱获得的糖度值为46-57。

表1显示了通过分析得到的实际糖度值，实际糖度值非常接近果碎粒的自然变化后果酱的糖度值。

水果渗透失水处理过程可变因素（渗透液浓度，时间，温度，水果和渗透液比率，渗透失水处理水果/渗透溶液比率）在最终配制中能进行优化组合处理，这样能进行通过封闭循环处理，最小程度化用水，并得到符合法律要求质量优良的产品。

表2 配方中配制猕猴桃果酱/橙果酱原料组成成分和比率
a ODKJ, 渗透失水处理猕猴桃果酱; ODOM, 渗透失水处理橙果酱; TOM,传统橙果酱.
b 100g猕猴桃果酱/橙果酱c质量平衡推断[浓缩阶段蒸发水质量：7g/100g初始混合物（新鲜
水果：糖50：50）].
配制产品的物理化学参数（水分活度，Xw和pH值）在市售果酱产品物化参数范围内，虽然因为没有在配制中加入柠檬酸使得猕猴桃果酱酸度略低。

分别用相同数量和ph草莓，桃子，李子和杏制作果酱，然后对所有果酱产品进行了分析，产品pH值都介于3和4。

（Carbonell, Costell, & Duran,1991）表3显示果酱产品特征的彩色坐标[亮度（长*），色相角（高* ab）及铬（容积*ab）]。

市售猕猴桃果酱与其他果酱相比在澄明度或亮度上有显着差异，抽样样本(CDKJ)显得更亮，很可能是因为含有较高水分。

配制的果酱（ODKJ）比非营养市售果酱显得更亮。

橙果酱在亮度上有很大的变化性，配制的产品（TOM和ODOM)显得最亮，但它们两者之间没有显著差异。

表3 市售和配制猕猴桃果酱/橙果酱颜色参数（平均值±标准差，重复三次实验）
A CTKJ, 市售传统猕猴桃果酱; CDKJ, 市售营养猕猴桃果酱; ODKJ, 渗透失水处理猕猴桃果酱; COM,市售橙果酱; TOM, 传统橙果酱;ODOM, 渗透失水处理橙果酱.
插图.2.市售和配制猕猴桃果酱/橙果酱a*-b*染色面（CTKJ，市售传统的猕猴桃果酱; CDKJ，市售营养猕猴桃果酱; ODKJ，渗透脱水处理的猕猴桃果酱; COM，市售橙果酱; TOM,传统橙果酱，ODOM,渗透失水处理的橘子果酱）。

插图2 显示猕猴桃果酱/橙果酱在a *- b *染色面上的染色位置。

猕猴桃果酱样品出现团聚的黄色物（不是绿色），并接近低铬色（灰色）。

肉眼比较配制果酱和非营养市售果酱产品就能观察它们之间的差异：ODKJ比CTKJ显得更新鲜和有光泽。

橙果酱都聚集在a *- b *平面的两个地方。

配制的橙果酱样本和某些市售橙果酱样本，它显示高铬值和色调偏黄，而另一组调查结果则显示低铬值和色调偏红。

当ODOM与TOM相比较时，色泽属性是第一个最易对比观察的。

因此，对于猕猴桃和橙的果酱产品生产，水果渗透溶液的精心配制，避免浓缩加工步骤，
能使最终产品获得更好的色泽。

色泽被认为是第一感官属性，影响消费者对食品质量的整体接受度（克莱兹，1984年），这一结论表明在果酱制作中对水果进行渗透脱水处理的重要性。

市售和配制果酱产品的粘稠度用博斯特威克粘度计和反挤压测试进行评估。

前者是广泛用于工业生产控制。

然而，在反挤压试验中，当果酱屈服应力不超过重力作用时，胶凝产品能在流动中提供更有价值数据。

果酱不能在稠度计流动。

插图.3显示了猕猴桃和橙果酱产品在反挤压试验中获得了流动距离数据曲线。

绘制在图.3COM样本两条曲线涵盖所有获得的数据。

ODOM和TOM数据在于市售样本数据范围内。

对于猕猴桃果酱，可以观察到ODKJ比市售果酱样品稀释，这可以从最低的挤压力值来解释。

这可是因为在没有热处理条件下，导致果酱在液态阶段水果果胶之间没有相互结合。

因此，可以知道水果果胶能增加果酱产品的粘稠度。

这个作用可通过选择合适的增稠剂来代替。

插图.3. 猕猴桃果酱反挤压曲线（左边图像），橙果酱（CTKJ，市售传统的猕猴桃果酱; CDKJ，市售营养猕猴桃果酱; ODKJ，渗透失水处理的猕猴桃果酱;COM，市售橙果酱，TOM,传统橙果酱; ODOM,渗透失水处理都橙果酱）。

值得注意的是，反挤压模式显示了挤压力快速增加，直到产品开始流动，接下来，挤压力增加比较慢，这特别是体现在猕猴桃果酱产品上。

不溶性物质（果肉碎粒）逐渐堆积使得第二个步骤中挤压力增加，从而增加果酱流动阻力。

橙果酱产品在第二个步骤中挤压力-距离曲线大幅度倾斜支持这个猜测，现在市售果酱产品中含有较大数额不同尺寸和大小肉眼可见的水果碎
粒。

果碎粒越大观察到的曲线越斜。

为了避免了果碎粒过度集中对果酱流动性的影响，取离挤压力-距离曲线10mm下领域值(A10)作为参照样本。

表4显示了A10的数值及用样本果酱重量校正稠度计每个样品的流动距离。

营养橙果酱(CDKJ)在稠度计上不流动是因为它的凝胶稳定性。

对于橙果酱，在某些情况下是由于水果碎粒堆积钩住在两个隔间的弹簧门会导致样品流动出现障碍。

表4 市售和配制猕猴桃果酱/橙果酱流动性能（平均值±标准差，三次重复试验）
a CTKJ,市售传统猕猴桃果酱; CDKJ, 市售营养猕猴桃果酱; ODKJ, 渗透失水处理猕猴桃果酱;
COM,市售橙果酱; TOM, 传统橙果酱;ODOM,渗透失水处理橙果酱.b 胶凝粘稠度.
插图.4显示橙果酱产品A10和d/w之间的关系。

观察到它们之间有相当密切的相关性，就像预计一样，挤压力数值越大，D/w值越低。

然而，某些样品不遵循通常模式，TOM和ODOM就是其中的例子。

不同胶凝剂的使用对这过程有重要影响。

胶凝剂赋予果酱弱凝胶结构，其屈服应力几乎不超出重力作用，但是当凝胶剂被分解，粘稠度就会不高。

插图.4. A10域（离挤压力-距离曲线10mm距离的域）反挤压参数和橙果酱Bostwick粘稠度之间关系（COM, 市售橙果酱; TOM, 传统橙果酱; ODOM, 渗透失水处理橙果酱）。

结论
由渗透失水处理水果和渗透溶液制作果酱或橙果酱不仅可避免热处理，制成果酱可媲美甚至优于传统方法制备的市售果酱产品。

我们需要对果酱产品质量的稳定性和运动变化性进行评估，这是为了确定该产品的储存条件。

参考资料
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Jam manufacture with osmodehydrated fruit
E. Garcıa-Martınez, G. Ruiz-Diaz, J. Martınez-Monzo, M.M. Camacho,
N. Martınez-Navarrete, A. Chiralt*
Department of Food Technology, Universidad Polite ´cnica de Valencia, PO Box
22012, 46071 Valencia, Spain
Received 5 December 2000; received in revised form 13 March 2001; accepted 8 July
2001
Abstract
Jams are made from fruit and sugar mixed in proportions so that the final product contains a minimum fruit content of 30% and 45°Brix minimum. Traditional manufacturing methods require concentration by heat treatments, which promotes quality changes that affect sensory and nutritional properties, the latter related mainly to ascorbic acid losses. An alternative to concentration is to incorporate previously dehydrated fruit, avoiding thermal treatment. Osmotic dehydration with sugar solutions has been described as a suitable method for preserving fruit quality to a great extent. On the other hand, osmotic solution becomes enriched with water-soluble fruit components after osmotic treatment。

In this work, the production of kiwi and orange jam by using osmotically dehydrated fruits mixed with osmotic solution, without thermal treatment, has been studied. Physical (colour and mechanical properties) and physico-chemical properties (a w, °Brix, moisture content, pH, acidity) of obtained products have been analysed and compared with those determined for commercial available products.
Author Keywords: Jam; Marmalade; Osmotic dehydration; Kiwifruit; Orange 1Introduction
As defined by UNE regulation (1974), jams are products formulated from a minimum fruit content of 40% (30% for citrics) and a final soluble solid content of 45°Brix. Moreover, some additives such as citric acid or gelling agents, commonly pectin, can be adde。

In traditional jam manufacture, all the ingredients are mixed in adequate proportions and the mix is concentrated by applying thermal treatments at normal or reduced pressure to reach the required final soluble content. This process
leads to a thickened or gelled consistency, ensures the destruction of fruit enzymes, extracts some of the pectin from the fruit and concentrates the product to a point where, as a result of its acidity and reduced water activity, it is self-preserving ( May, 1997). Nevertheless, it also implies undesirable changes in colour, texture, nutritive value and flavour properties due to temperatures achieved in the cooking process.
An alternative in jam formulation is to use previously dehydrated fruit, thus reducing the concentration requirements ( Shi, Chiralt, Fito, Serra, Escoin, & Gasque, 1996). In this sense, osmotic dehydration allows us to obtain fruit products that have good flavour, aroma and nutritional content and small mineral and vitamin losses ( Dixon; Lenart and Ponting). In this process, water is transferred from the fruit to a concentrated sugar (generally sucrose) solution at mild temperatures without undergoing a phase change. Sucrose is preventing fruit decolouration by non-enzymatic and enzymatic oxidative browning, the fruit remaining fresh and more natural ( Ponting; Ponting and Shi).
Furthermore, the osmotic solution (OS) used for fruit dehydration can be adequately formulated with additives and added to fruit in order to formulate jams. n this way, solutes possibly lost during the osmotic dehydration (OD) process can be recovered. In this sense, new jam technology was developed in which osmotically dehydrated fruits and osmotic solutions were used directly in strawberry jam processing (Shi et al., 1996). Since the fruit undergoes a process at lower temperatures (35–40 °C) for only a short time during osmotic dehydration, the new jam product exhibits superior natural colour, good flavour and overall quality.
The objective of this paper is the comparison of physical and physicochemical quality parameters of kiwifruit jam and orange marmalade produced by applying the new procedure and of commercial available products. Special attention was paid to colour attributes, as these are especially affected by heating treatments.
2 Materials and methods
2.1 Raw materials
2.1.1 Commercial jams/marmalades
Eight traditionally produced orange marmalade samples (COM) and two kiwifruit jam samples (CTKJ and CDKJ), purchased in local supermarkets in Valencia (Spain), were used in the study. No more commercial kiwifruit jams were found, one of them (CDKJ) being a dietetic product formulated with fructose.
2.1.2 Fruit
Fresh orange (Citrus sinensis) of the cultivar Valencia Late, and kiwifruit (Actinidia chinensis P.) were purchased in local markets in Valencia (Spain).
2.1.3 Osmotic solution
OS was prepared by mixing an amount of food grade commercial sucrose with slightly heated distilled water until it was completely dissolved, to form a 70°Brix (for orange samples) and 55°Brix syrup (for kiwi fruit samples). Concentration of OS in each case was established on the basis of previous kinetic studies of fruit osmodehydration and the legal and commercial requirements for final jam/marmalade composition.
2.1.4 Gelling agent
Two different gelling agents were used. Kiwifruit jam was produced with high methoxil pectin-rapid set (distributed by Hercules Incorporated, Denmark) and orange marmalade with NAP (a commercial gellan gum and pectin mixture distributed by Hahn & Co, Germany).
2.1.5 Acidity agent
Citric acid was added only to orange marmalades to reach a final pH of 3.5–3.6.
2.2 Jam/marmalade elaboration procedure
Kiwifruit jam was produced by using previously OD fruit, avoiding thermal treatment (sample ODKJ) whereas orange marmalades were prepared by both the traditional method (TOM) and the process with OD fruit (ODOM).
2.2.1 Traditional process
Fresh orange slices mixed with commercial sugar, NAP and citric acid were concentrated throughout a boiling process to obtain 56% soluble solid content.
2.2.2 Process with OD fruit
Samples were cut into slices (orange 0.5 cm in thickness and kiwifruit 1 cm in thickness) and osmodehydrated for 1 h at 30 °C in a stirred tank containing the corresponding OS. Slices were placed in baskets to keep them totally immersed in the solution.
For jam/marmalade production, an established amount of the OS used was mixed with the gelling and acidity agents, and heated till 80 °C in order to dissolve them. OD orange and kiwifruit slices were ground in a shredder (Kenwood), and an adequate proportion mixed with the formulated OS. Products obtained by this procedure were called osmodehydrated orange marmalade (ODOM) and osmodehydrated kiwifruit jam (ODKJ).
All jams/marmalades were put into glass jars and stored under refrigeration conditions (6 °C) till analysis.
2.3 Analysis
2.3.1 Physicochemical properties
Moisture content was determined using AOAC 20103 method (1980). Soluble solids were determined by measuring the °Brix at 20 °C (Abbe Atago 89553 refractometer). Water activity (aw) was measured by using a dew point hygrometer (Decagon CX-2) and pH in a Crison microPH 2001 pH-meter. Acidity (expressed as g citric acid/100-g sample) was determined by titration following AOAC 942.15 method (1980). Each analysis was carried out in triplicate.
2.3.2 Colour measurement
Colour was measured by means of reflectance spectra in a Minolta CM-1000 Spectro-photometer. CIE L* a* b* colour coordinates (D65, 10°) were obtained. For
measurements, samples were placed in a white cup and covered with optical glass.
2.3.3 Flow properties
These were evaluated throughout two different analyses:
Back-extrusion test: Sample (at 20 °C ) was placed in a bakery glass (6 cm diameter), and back-extruded with a 4.95 cm diameter plunger at 1 mm/s deformation rate by using a Texture analyser TA. XT2 (Stable Micro Systems).
Consistency test: The flow distance of a controlled sample weight for a constant time was measured by using a Bostwick consistometer.
It consists of a level stainless-steel trough divided into two compartments. The first one initially containing the sample (5×5×3.8 cm) is separated from the second by means of a spring-loaded gate. The second compartment is a trough 5 cm wide, 24 cm long, and about 2.5 cm high and has a series of parallel lines drawn across the floor at 0.5-cm intervals. Once the gate is opened, the distance the sample flows in 30 s is measured (Bourne, 1982).
3 Results and discussion
Table 1 shows the ingredients of commercial jams/marmalades as they appear on the product label also as the results of their physicochemical characterisation. A wide range for °Brix, moisture content and aw values was observed for both commercial kiwifruit and orange products.
For kiwi products, while dietetic jam does not comply with the legally stipulated minimal °Brix value (UNE-), the CTKJ sample greatly exceeds this limit. In orange products, the °Brix values range between 49 and 66, while the specified fruit content on the label is lower than that required by UNE in the samples COM1 and COM7. The aw values are in agreement with the °Brix values as can be seen in Fig. 1 where in addition the predicted aw values according to Norrish (1966) are plotted, assuming that the only soluble sugar in the product is sucrose (S) or glucose-fructose (G/F). All experimental values lie between the two predicted lines in agreement with the product sugar constituents (different ratio of sucrose, glucose and fructose). The experimental values
of the products obtained in the laboratory (ODKJ, TOM and ODOM) lie on the sucrose line according to their major sugar component which was added in formulation. The lower the product aw (or the higher the °Brix), the greater the product stability.
Table1. Components and measured physico -chemical properties (mean±standard deviation, three replicates) of commercial available and formulated jams/marmalade
a CTKJ, commercial traditional kiwifruit jam; CDKJ, commercial dietetic kiwifruit jam; ODKJ, osmodehydrated kiwifruit jam; COM, commercial orange marmalade; TOM, traditional orange marmalade; ODOM, osmodehydrated orange marmalade.
b g Water/100-g sample.
c g Citric acid/100-g sample.
d 75% Fructos
e syrup.
e Without specification o
f the ingredient amount in the label.
Fig. 1. Water activity–Brix map for commercial and formulated kiwifruit jams and orange marmalade. Lines are the predicted values (Norrish, 1966) assuming sucrose (S) or glucose/fructose (G/F) as the only soluble solids (ODKJ, osmodehydrated kiwifruit jam; TOM, traditional orange marmalade; ODOM, osmodehydrated orange marmalade).
Given the wide composition range of commercial products, the jam/marmalade
ingredient formulation was selected to obtain products inside this range but at the same time complying with the Spanish legal requirementsUNE. (1974). Table 2 shows the ingredients used in each case, together with their composition. As can be seen, ODKJ and ODOM samples contained 37.8 and 44.3 g of fresh fruit per 100 g of final product. The ratio OD fruit-OS (and sucrose in ODOM) in the mix was established from mass balances to obtain 46 and 57 °Brix, respectively, in taking into account the composition of OD fruit and the OS. Table 1 shows the actual °Brix values obtained from analysis which are very close to those established, taking into account the natural variability of fruit pieces. The fruit OD process variables (OS concentration, time, temperature, fruit-OS ratio) and the osmodehydated fruit-OS ratio in the final formulation could be optimized in order to obtain closed cycles, minimising wastes, with an acceptable product quality that complies with legal requirements.
Table 2. Ratio and composition of ingredients in the formulated jams/marmalades
A ODKJ, osmodehydrated kiwifruit jam; ODOM, osmodehydrated orange marmalade; TOM, traditional orange
marmalade. b In 100 g of jam or marmalade. C Deduced from mass balances [mass of evaporated water in the concentration step: 7 g/100 g of initial mixture (fresh fruit: sucrose 50:50)].
Physico-chemical parameters (aw, Xw and pH) of formulated products lie inside the range defined in commercial products, although acidity was slightly lower for kiwifruit products due to the fact that no citric acid was added in formulation. For all analysed products, pH ranged between 3 and 4, in the same magnitude of order as the pH of other
jams made of strawberry, peach, plum and apricot (Carbonell, Costell, & Duran, 1991). Colour coordinates [luminosity (L*), hue angle (h*ab) and chrome (C*ab)] of characterised products appear in Table 3. Commercial kiwifruit jams showed a significant difference in clarity or luminosity, the dietetic sample (CDKJ) appearing lighter, probably due to its greater water content. The formulated sample (ODKJ) was also lighter than the non-dietetic commercial one. Orange marmalades showed a wide variability in luminosity, the formulated products (both TOM and ODOM) again being the lightest, with no notable differences between them.
Table 3 Colour parameters (mean±standard deviation, three replicates) of commercial and
formulated jams/marmaladesa
A CTKJ, commercial traditional kiwifruit jam; CDKJ, commercial dietetic kiwifruit jam; ODKJ, osmodehydrated kiwifruit jam; COM,commercial orange marmalade; TOM, traditional orange marmalade;ODOM, osmodehydrated orange marmalade.
Fig. 2. a*–b* chromatic plane for commercial and formulated jams/marmalades (CTKJ, commercial traditional kiwifruit jam; CDKJ, commercial dietetic kiwifruit jam; ODKJ, osmodehydrated kiwifruit jam;COM, commercial orange marmalade; TOM, traditional orange marmalade; ODOM, osmodehydrated orange marmalade).
Fig. 2 shows the chromatic locus of jam/marmalades in the a*–b* chromatic plane. Kiwifruit samples appear grouped around the yellow hue (no green) close to the low chrome (grey) zone. Visual comparisons between formulated and non-dietetic commercial jam products reflected the observed differences: greenness and brightness in ODKJ are greater than in CTKJ.
Orange marmalades are grouped in two areas in the a*–b* plane. One of these, containing the formulated samples and some commercial ones, shows a more yellow hue with greater chrome values, whereas the other group shows lower chrome values and a redder hue. When ODOM is compared with TOM, better colour attributes were observed for the first one. So, for both kiwi and orange products, the OD of the fruit prior to formulation, avoiding the concentration step, seems to preserve the colour of the final product better. Since colour is considered to be the first sensory attribute defining consumers’ acceptability of the overall food quality (Clydesdale, 1984), the obtained results point to the interest of fruit osmodehydration in jam processing. Consistency of commercial and formulated products was evaluated by using Bostwick consistometer and back-extrusion tests. The former is a method widely used in industrial control. Nevertheless, the back-extrusion test can provide more reproducible values while allowing the flow of gel products, whose yield stress is not exceeded by gravitational force. These cannot flow in the consistometer.
Fig. 3 shows some curves obtained in the back-extrusion test for kiwi and orange products. The two curves of COM samples plotted in Fig. 3 cover the range defined by all of them. Curves for ODOM and TOM lie in the range of the commercial samples. For kiwifruit jams, ODKJ showed much less consistency than that observed in commercial samples, as deduced from the lowest force values. This can be due to the lack of the incorporation of the fruit pectin to the liquid phase in line with the absence of thermal treatment. So, the fruit pectin would scarcely contribute to the product thickness. This effect may be corrected by selecting an adequate gelling agent.。