April 09, 2018

10/04/2018: Professional crop cleaning as an essential contribution to grain hygiene management

by Dr Heike Knöerzer, Head of Knowledge Management, Petkus Holding GmbH

Losses begin after the harvest. According to official estimates, about one third of the grain produced for food purposes is lost during post-harvest processes such as storing, drying, cleaning or milling.

This corresponds to approximately 1.3 billion tons with a value of one trillion US dollars per year, as Deepak Kumar and Prasanta Kalita summarised in their report in the “Foods” magazine 6 (1) 2017. Process engineering with regard to optimising post-harvest processes receives little attention from a scientific perspective. Less than five percent of research funding has been allocated to this critical issue in recent years.
 


Mechanical, aerodynamic and optical sorting technologies within grain processing are an essential contribution to hygiene management. However, they are hardly considered as such and thus, far are too rarely included. Between grain storage and food processing, there is great potential for minimising losses, ensuring product quality and generating added value.

Many grain lots have to be discarded because they have been attacked in part by insects, contaminated with mycotoxins or because they contain an unacceptable level of critical impurities (e.g. invasive alien species) or closely related species. Already popped popcorn maize, red coloured bran in white rice, sclerotinia in sunflowers or ergot in rye can destroy an entire field production if no adequate processing technology is available. Bean weevils, ambrosia, cuscuta, deoxynivalenol or aflatoxin lead to post-harvest death if processing is inadequate. By contrast, investments in modern technologies are paying off.

Hamid Alavi (World Bank) reports that small to medium scale village mills in South-East Asia achieve only 57 percent instead of the theoretical head rice recovery of 70-73 percent. As decisive reasons, he claims inadequate cleaning and calibration as well as insufficient maintenance of the machines. Traditional winnowing causes losses of around four percent of total field production, which according to FAO data (Ø 2012 - 2016) amounts to around 0.2 million tonnes of grain per year in Africa, Central America and South-East Asia alone. In Europe, an estimated one to two percent loss of good grain is estimated to result in an annual loss of approximately 9500 tonnes within the pre-cleaning process alone. This corresponds to 17 million one kg loaves of bread.

Hygiene begins with professional crop cleaning
It already starts with pre-cleaning as an essential step. A large proportion of dust, soil, stalks, chaff, impurities, and parts of heads, cobs or panicles are removed here. From a grain trader’s perspective, the primary task of pre-cleaning is to waste as little sellable product as possible and to sort out as many impurities as necessary in order to sufficiently dry and store the grain afterwards. Pre-cleaning significantly reduces storage losses. Inhomogeneous material means inhomogeneous drying and moist spots in storage. If you clean improperly, you will be faced with waste later on.

In addition to capacity, it is important that cleaning is efficient and the loss of good grain is minimised. Drum cleaners, screening machines or air screen cleaners are used for pre-cleaning. Petkus Technologie GmbH in Wutha-Farnroda, Thuringia, relies primarily on the linear oscillation principle for its screen cleaners because this achieves a very precise cleaning performance.

In the linear oscillating system, the screens vibrate horizontally, meaning they carry out a linear oscillating movement driven by an eccentric shaft and unbalance motors. Operation is according to the ejection principle. As a result, the kernels are arranged parallel to the perforated sieve slots, improving flow and sorting accuracy.

Read the full article, HERE.

Visit the Petkus website, HERE.
 

The Global Miller
This blog is maintained by The Global Miller staff and is supported by the magazine Milling and Grain
which is published by Perendale Publishers Limited.


For additional daily news from milling around the world: global-milling.com

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