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Spray drying of fruit juice with vegetable fibre as a carrier

机译:以植物纤维为载体的果汁喷雾干燥

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摘要

The production of free flowing powder by spray drying of sugar-acid rich foods requires an appropriate carrier. High molecular weight materials such as maltodextrins are commercially used as a drying aid because of their high glass transition temperature (Tg). Alternatively, fibre-rich by-products from fruit and vegetable juice processing might provide high molecular weight elements that are suitable as a drying support. This study aimed to understand the variables affecting the spray-dried product of fruit juice so that non-sticky fibre-based juice powder could be obtained.Freeze dried carrot fibre was centrifically-milled to 50-100 µm sizes. Three sugar determination methods; enzymatic, enzyme membrane and HPLC with RID, were compared. The freeze drying performance of fructose, fructose + carrot fibre and fructose + carrot fibre + malic acid had the glass transition temperatures measured by differential scanning calorimetry (DSC) at 0.1 °C min-1. The results from the freeze drying were used as a key for the possibility of spray dried apple juice + carrot fibre. Similar methods were used to study freeze dried fructose + maltodextrin (DE max 9.8) and fructose + maltodextrin + malic acid. Dried sucrose, glucose and fructose were used to study glass transition temperature of melted amorphous sugars and mixtures by the visual experiment and DSC at 0.1°C min-1 of heating and cooling scans. The Gordon-Taylor equation was used to predict the Tg of anhydrous two-sugar mixtures from experimental and literature data. The Coachman and Karaze equation was used to predict Tg of three-sugar mixtures and compared to the experimental data. Spray dried powders of fructose + carrot fibre of 30, 40, 50, 60 and 70% w/w and apple juice concentrate + carrot fibre of 30, 40, 50, 60, 70% w/w at 165/75°C inlet/outlet temperature in a laboratory scale drier were compared to that of fructose + maltodextrin (DE max 9.8) and apple juice concentrate + maltodextrin of 50, 60 and 70% w/w (dry basis). Dielectric analysis in the range 200 Hz -1 MHz between 10-105 °C were applied to find the onset Tg (based on DSC results) from freeze dried mixtures of 14, 21, and 28% w/w (dry basis) carrot fibre+ fructose. The enzymatic method was found to be the most accurate method for sugar determination of fruit juice but the HPLC method was the most practical one. The results of Tg values of sugars and mixtures melted showed that the Tg values from heating and cooling scans of fructose, glucose and sucrose were in good agreement with literature. Fructose acted as a plasticizer; an increase in the fructose fraction decreased the Tg of sugar mixtures. Sucrose increased the Tg of the mixtures while the Tg of the three-sugar mixtures was less variable when there was a moderate to high proportion of glucose. The visual Tg values of sugars and mixtures were 7-28 °C higher than the onset DSC heating and cooling Tg values. This result suggested that more than one method should be used to study the glass transition of substances. The Gordon-Taylor equation did not fit well the Tg values of the dry sugars and their mixtures from this experiment. The variations might have been due to the degradation of sugar samples on the melting process. The Coachman and Karaze equation gave a good prediction of the three-sugar mixtures from this experiment.The carrot fibre was found to be crystalline. Carrot fibre increased the Tg of freeze dried fructose and decreased stickiness of fructose. Increasing malic acid fraction decreased Tg of the mixtures. Freeze dried fructose + maltodextrin showed higher hygroscopicity than freeze dried fructose + carrot fibre. It was not possible to determine Tg of fructose + maltodextrin + malic acid due to the swelling and hygroscopicity of the freeze dried samples. Tg values of freeze dried fructose + carrot fibre and fructose + maltodextrin were found to high enough to allow spray drying of these mixtures. The minimum fraction of carrot fibre to facilitate spray drying of fructose and apple juice concentrate was found to be 30%. Mixtures with maltodextrin at a fraction lower than 50% could not be successfully spray dried. When spray drying fructose + carrot fibre, apple juice + carrot fibre, fructose + maltodextrin and apple juice + maltodextrin at the appropriate ratios most of the powder stuck to the drier walls. The powder swept from the wall was free flowing with moisture content of approximately 2-4%. The Tg values of these powder indicated the wall build-up might be avoided in larger scale drying. Tg values of spray dried powder from the mixtures with fibre and maltodextrin were found to be not very different. The yield from mixtures with carrot fibre was three times higher than those of mixtures with maltodextrin. This cast doubts that Tg alone could be a good indicator for the stickiness of spray dried material. The microscope images and DSC scans of spray dried powders of fructose + carrot fibre and apple juice + carrot fibre showed crystalline material. The particle of spray dried fructose + maltodextrin and apple juice + maltodextrin were mostly amorphous. The crystals are more physically and chemically stable than the amorphous form. Thus carrot fibre is a good additive in spray drying of fruit juice. Dielectric analysis at low frequency was able to possible detect Tg of single and double components. For food polymer with many components it was found that Tg value was not consistently dependent on frequency. In conclusion, carrot fibre was a more effective carrier for spray drying than maltodextrin when compared on a mass basis and spray drying condition. Since edible fibre is an essential element needed by the human body, spray drying of fruit juice using fibre as a carrier showed the great potential of fibre in the application of fruit juice spray drying. In the case of clear juice, after reconstitution, the fibre can be easily separated from the juice as there seemed to be no chemical binding between the juice and the fibre during the spray drying process.
机译:通过喷雾干燥富含糖酸的食物来生产自由流动的粉末需要合适的载体。商业上使用诸如麦芽糖糊精的高分子量材料作为干燥助剂,因为它们的玻璃化转变温度(Tg)高。或者,来自水果和蔬菜汁加工的富含纤维的副产物可能提供适合用作干燥载体的高分子量元素。这项研究旨在了解影响果汁喷雾干燥产品的变量,从而获得非粘性纤维基果汁粉。将冷冻干燥的胡萝卜纤维离心研磨成50-100 µm的尺寸。三种测糖方法;酶,酶膜和具有RID的HPLC进行了比较。果糖,果糖+胡萝卜纤维和果糖+胡萝卜纤维+苹果酸的冷冻干燥性能具有通过差示扫描量热法(DSC)在0.1℃min-1下测量的玻璃化转变温度。冷冻干燥的结果用作喷雾干燥苹果汁+胡萝卜纤维的可能性的关键。使用相似的方法研究冷冻干燥的果糖+麦芽糖糊精(DE max 9.8)和果糖+麦芽糖糊精+苹果酸。通过视觉实验和DSC在0.1°C min-1的加热和冷却扫描中,使用干燥的蔗糖,葡萄糖和果糖研究熔融无定形糖及其混合物的玻璃化转变温度。 Gordon-Taylor方程用于根据实验和文献数据预测无水二糖混合物的Tg。 Coachman和Karaze方程用于预测三糖混合物的Tg,并与实验数据进行比较。在165/75°C入口处将果糖+ 30、40、50、60和70%w / w的胡萝卜纤维和苹果汁浓缩物+ 30、40、50、60、70、70%w / w的胡萝卜纤维喷雾干燥粉末将实验室规模的干燥器中的/出口温度与果糖+麦芽糖糊精(DE max 9.8)和苹果汁浓缩物+麦芽糖糊精以50、60和70%w / w(干基)的温度进行比较。在10-105°C之间进行200 Hz -1 MHz范围内的介电分析,以从14、21和28%w / w(干基)胡萝卜纤维的冷冻干燥混合物中找到起始Tg(基于DSC结果)果糖。酶法是测定果汁中糖分的最准确方法,而HPLC法则是最实用的方法。糖和熔融混合物的Tg值的结果表明,果糖,葡萄糖和蔗糖的加热和冷却扫描得到的Tg值与文献吻合。果糖起增塑剂的作用。果糖分数的增加降低了糖混合物的Tg。当葡萄糖的比例中等至高时,蔗糖增加了混合物的Tg,而三糖混合物的Tg的变化较小。糖和混合物的可见Tg值比开始的DSC加热和冷却Tg值高7-28°C。该结果表明,应使用多种方法来研究物质的玻璃化转变。 Gordon-Taylor方程与本实验中的干糖及其混合物的Tg值不太吻合。差异可能是由于糖样品在融化过程中的降解。 Coachman和Karaze方程很好地预测了该实验中的三糖混合物,发现胡萝卜纤维是结晶的。胡萝卜纤维增加了冷冻干燥果糖的Tg,降低了果糖的粘性。苹果酸分数的增加降低了混合物的Tg。冷冻干燥的果糖+麦芽糊精比冷冻干燥的果糖+胡萝卜纤维显示出更高的吸湿性。由于冻干样品的溶胀和吸湿性,无法确定果糖+麦芽糖糊精+苹果酸的Tg。发现冷冻干燥的果糖+胡萝卜纤维和果糖+麦芽糖糊精的Tg值足够高,可以喷雾干燥这些混合物。发现可促进果糖和苹果汁浓缩物喷雾干燥的胡萝卜纤维的最小含量为30%。麦芽糖糊精含量低于50%的混合物无法成功喷雾干燥。喷雾干燥时,果糖+胡萝卜纤维,苹果汁+胡萝卜纤维,果糖+麦芽糖糊精和苹果汁+麦芽糖糊精的比例适当,大多数粉末会粘在干燥壁上。从壁上扫出的粉末自由流动,水分含量约为2-4%。这些粉末的Tg值表明在大规模干燥中可以避免壁的堆积。发现来自具有纤维和麦芽糊精的混合物的喷雾干燥粉末的Tg值相差不大。胡萝卜纤维混合物的收率比麦芽糊精混合物高三倍。这使人们怀疑单独使用Tg能否很好地指示喷雾干燥材料的粘性。果糖+胡萝卜纤维和苹果汁+胡萝卜纤维的喷雾干燥粉末的显微镜图像和DSC扫描显示结晶物质。喷雾干燥的果糖+麦芽糖糊精和苹果汁+麦芽糖糊精的颗粒大部分是无定形的。晶体比无定形形式在物理和化学上更稳定。因此,胡萝卜纤维是果汁喷雾干燥中的良好添加剂。低频介电分析能够检测单组分和双组分的Tg。对于具有许多成分的食品聚合物,发现Tg值并非始终取决于频率。总之,按质量和喷雾干燥条件进行比较,胡萝卜纤维比麦芽糊精是喷雾干燥更有效的载体。由于食用纤维是人体必需的必需元素,因此以纤维为载体的果汁喷雾干燥显示了纤维在果汁喷雾干燥应用中的巨大潜力。如果是纯净果汁,则在重构后,纤维可以很容易地从果汁中分离出来,因为在喷雾干燥过程中,果汁和纤维之间似乎没有化学结合。

著录项

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    Cheuyglintase Kloyjai;

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  • 年度 2009
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