面食生产、干燥、包装

意大利是意大利面制造的国家，随着相关技术和机械的发展，已经并仍然有他们的顶级表现。从1900年开始，人工干燥过程使意大利面食在工业水平上生产，因此首先分销到意大利的所有地区，然后是国际(包括大量出口到美国)。后来，进口国家开始生产机器来生产和烘干他们自己的意大利面。干燥过程是工业化面食生产的最后一个主要步骤，它是大大延长产品保质期(数月至数年)的基础。随着干燥，相对湿度从未发酵面团的32-35%到不超过最后干燥面团的12.5%。这个水平有时甚至低于小麦粉的初始湿度(例如14-15%)。如此深的干燥程度是无法实现自然干燥在可接受的时间，因此房间或橱柜在控制温度和湿度被广泛使用。干燥过程导致意大利面表面形成一种“外壳”，但随后湿度会在“心”和表面之间重新分配。由于进口产品和干燥柜的条件是非常不同的，一个热力学平衡条件是突然建立在干燥的开始，然后传质提供提取剩余的水从大部分的食品。在固体如面团基质中的液体扩散机制携带水在样品和空气之间的界面，在那里蒸发发生。 Then, water diffuses as vapour through a gas medium often by a forced convection mechanism present in the drying cabinet in order to facilitate the process. The water must be extracted so that the tension generated does not exceed the product’s limit of elasticity: if this occurs, pasta will be damaged to a greater or lesser extent (cracks, splits, veining, etc.). Regarding the controlled temperatures applied for pasta exsiccation, it is possible to distinguish two different approaches:

低温干燥:这是一种更传统的程序，涉及在相对较低的温度(60-70°C)下延长干燥时间(约10-15小时或更长)。由于这个原因，大量产品的干燥需要很大的空间和时间，因此最终的面食成本相当高。这是一种干燥过程，在许多传统和著名的意大利面食生产工厂仍在使用，使用从小麦粉开始的高级配料，包括用于制作面团的水。

高温干燥:根据面食的厚度、形状和面团的初始湿度，面食在60至120°C的温度下干燥2至10小时。这些数值只是指示性的，因为不同的生产工厂可以使用许多不同的高温干燥协议:事实上，高温(HT)和非常高温(VHT)干燥周期是这种方法的子组。高温的一个好处是可以在烹饪过程中创造出性能良好的意大利面，即使煮的时间延长了几分钟，仍能保持正确的稠度。事实上，相比HT面食和VHT面食，后者在感官评价、烹饪后在烹饪介质(水)中分散的总有机物、烹饪失重等方面的质量得分更高。高温干燥的这些有利影响可能取决于淀粉颗粒的构象变化(在x射线衍射中很明显)和谷蛋白变性。此外，即使用于生面团的小麦粉质量不高，这些影响也经常存在。从微生物学的角度来看，使用高温的另一个优点是获得了一种极其安全的产品。尽管有这些优点，包括由于干燥时间短得多而带来的经济效益，但高温干燥方法可能会导致一些风险和对最终产品的损害，例如，热机械应力(面食以不同速度干燥的不同区域导致面食断裂)和非酶褐变(美拉德反应)。如果参数没有得到很好的控制，例如温度过高和/或时间过长，就会出现这些问题。 In order to overcome these risks, controlled drying cycles are often applied, where strong exsiccation steps characterized by high temperature and low air humidity are forerun by a pre-drying step and followed by “recovery stages” at low temperature and higher air moisture content, to allow re-equilibrium deep inside the pasta. In this way, it is possible to avoid the onset of internal humidity gradient and the formation of the surface “crust”, which would hinder any further exsiccation. As a result of a good drying cycle programming, overall pasta water loss is faster, and final product quality is higher. Of course, in order to realize these drying cycles, it is necessary a plant design capable of finely tuning process conditions and alternating “fast” and “soft” drying conditions. Regarding the effect of the drying step on pasta sensory characteristics, the multi-step Maillard reactions can play a role both on appearance and flavours of dry pasta: the relevance of these reactions not only depends on temperature level and length of its application, but also on raw material composition, in particular percentage of proteins and reducing sugars (both precursors of Maillard reactions products). In fact, high temperature dried pasta often has a darker/yellower aspect compared to low temperature dried one. The yellow colour could also be partly due to wheat selection in the last years, more oriented to carotenoid-rich grains. Maillard reaction entity can be monitored not only evaluating pasta colour but also, more accurately, measuring some marker substances (e.g. furosine) formation. At the end of the drying process, even if the value of moisture in the pasta is the desired one, it is necessary for it to be distributed uniformly inside the product so that all moisture gradients are zeroed (especially if the pasta was dried with WHT cycles and in a short time). The stabilization phase must keep the final moisture level in the product unchanged, even if a slight further decrease in moisture is possible. After completing stabilization, pasta can at last be cooled and reach the condition of being thermally balanced with the environment, ready for packaging. The most used pasta packaging is flow pack plastic, either for supermarket size pasta (500 g to 1 kg) or ho.re.ca sector (5 to 10 kg). Pasta shapes more prone to mechanical fractures (e.g. egg pasta) or higher range quality pasta are often packed in paper based trays or boxes, with or without plastic sleeves or windows.

参考文献

米利奥里，杜德华，杜德华, 2005年。高品质面食干燥模型:质量指标及工业应用。食品工程学报，71:242-251;

Güler S.， Köksel H.，吴炳光, 2002年。工业面食干燥温度对淀粉性质和面食品质的影响。国际食品研究，35(5):421-427。

由丽塔洛伦西尼