21 February 2024

Controlling Moisture to Minimise Food Waste

Food is a vital and valuable commodity, yet according to Earth.Org1 around one-third of the world’s food, amounting to 1.3 billion tons, is either lost or wasted.

The benefits of reducing this waste are obvious: reducing the cost of food whilst also increasing the supply.

Incorrect levels of moisture can be a major problem for the food industry. Failure to control moisture can result in the food becoming spoilt, being unsalable or inedible.

This article discusses various types of food waste and introduces how moisture control can be beneficial, both in the reduction of waste and in the subsequent processing of the waste.

The article then gives two examples of successful applications incorporating moisture control and the benefits achieved. These real-life examples are also representative of many other similar applications when processing food.

What is Food Waste?

It is important to clearly define the meaning of food waste as it is a term that is open to interpretation. There are many causes of food waste, which can be split into three distinct types, occurring at various stages within the food supply chain.

Manufacturing Waste

Manufacturing waste is waste created during the production processes. This may be excess product, for example, trimmings, or by-product waste such as fat or bones.

Other examples of manufacturing waste are:

  • Losses incurred due to mechanical processing, such as the dust created during flour milling.
  • Spoilage due to incorrect processing or inadequate process control.
  • Non-compliance waste such as mycotoxin growth.
  • Quality waste due to product not meeting specifications.
  • Energy waste due to inefficiencies in process management.

Most of these forms of waste may be reduced by better control of the moisture content throughout the process. Moisture levels in ingredients at various stages of production can affect the taste, the ability to process efficiently, machine operating temperature and machine wear.

Processes such as weighing, mixing, milling, and drying all benefit from precise moisture control. Moisture content is also a major determinant of a product’s physical integrity, nutritional value, texture, and the ability for it to be properly moulded, such as for a pellet. It also affects the product’s shelf life.

Industrial Waste

Industrial waste is generated by the manufacturing process: it can be thought of as the “leftovers” after processing. A waste element is common to most food manufacturing processes: for example, when sugar is extracted from sugar beet, a pulp remains. A similar residue results from the production of rapeseed and other oils.

Industrial food waste is typically post-processed into other food materials. For example, the sugar beet pulp and residual press cake from oil production are both typically used to manufacture animal feeds.

Harvesting can be considered part of the manufacturing process, and this also generates waste material as the crop is removed from the chaff. This type of waste is typically used to manufacture products such as fertiliser and biofuels.

Precise real-time measurement and control of moisture during various stages of the food manufacturing process aid waste reduction, help to re-process and re-purpose industrial waste efficiently.

Consumer Chain Waste

Consumer Chain waste occurs at the final stage of the food supply chain, at the suppliers, retailers and in the kitchens of final consumers.

This category encompasses out-of-date food, unsold or unsalable products, spoiled products and products damaged by incorrect handling or storage. This may be generated by a supermarket or food retailer, with examples such as coffee grinds or residual food and oils.

Consumer chain waste may be repurposed in a variety of ways. For example, it can be used to create animal feed in various forms, such as liquidised supermarket waste being used to feed insects.

Waste from consumption can also be recycled, for example, coffee grinds have a variety of uses, including being recycled into fertiliser, biofuel, or even used as a replacement for aggregates in the construction industry.

Producing a new product from consumer chain waste is often difficult, so waste food is often simply composted or burnt to generate energy. These processes also benefit from moisture measurement and control for optimum efficiency.

Moisture Control: A Key to Waste Reduction

Correct control of the moisture can reduce technical problems such as blockages, reduce machine wear and the likelihood of breakdowns as well as reduce energy consumption and increase yield. Correct final moisture levels also determine a product’s shelf-life.

Two well-established and successful examples are the use of Hydronix sensors to optimise animal feed production and rice processing. These solutions may also be applied to other foods and processes.

Moisture control in animal feed

In the production of animal feed, incorrect levels of moisture in the input mash cause problems in the pellet mill, resulting in dusty, crumbling pellets or soft, misshapen, sticky pellets with variable nutritional value. This results in the feed produced being unpalatable for the animal, going mouldy while being stored or simply having a reduced shelf life.

Controlling moisture is, therefore, a key part of feed production. Failure to ensure the correct levels will not only result in disappointed customers and poor business performance but also in higher levels of waste, machine wear and manufacturing problems.

Find out more details in this article on the benefits of moisture control in animal feed.

Moisture control in rice production

The correct control of the drying process of rice has significant benefits, from ensuring a high-quality product (as over-dried rice has a bitter in taste), a reduction in energy from over-drying, and most notably, reducing the volume of broken grains.

During the drying process, rice might circulate through a drier up to twelve times. A Hydronix sensor monitors the moisture of the rice as it is dried. For optimum results, the rice is not dried at a constant rate, instead, the drying process temperatures are continually adjusted to achieve optimum product quality and energy efficiency.

Correct adjustments of the drier ensure that the rice is dried quickly, but not too fast. This improves the final quality and ensures the rice is at the perfect moisture content for de-husking. Too wet rice and the kernels may be damaged; too dry, and the rice breaks and cannot be sold as a premium product.

One example is a Hydronix customer that processes rice in West Bengal, India.

After deploying moisture sensors, broken rice was reduced from 3% to just 0.5%. By cutting broken rice to one-sixth of the previous amount, the customer eliminated 4,000kg/week of waste, equivalent to US$1,668.00. As the plant operates for 48 weeks of the year, this results in a total annual saving of US$80,064.00 due to proper moisture control.

This is many times the initial cost of installation and is virtually maintenance-free.

The same principles and benefits apply across the depth and breadth of applications within the food processing industry. From grains, nuts, seeds and oil processing to sugar, powders, and waste.

Choosing the Best Sensor for the Job

The benefit of real-time moisture measurement, as opposed to offline laboratory tests, is that it allows a process to be adjusted without any time delay. Additionally, the use of multiple sensors at different points enables more advanced process control. The use of multiple sensors allows end-to-end process optimisation.

There are a number of different measurement technologies to choose from, and within this choice, there are also a number of manufacturers, each with their unique benefits and limitations.

If the wrong technology or sensor is selected for an application, instead of providing a solution, it can cause more problems as a result of incorrect readings or measurements that vary with ambient or material temperature.

This results in continual adjustment, needing high maintenance requirements with unreliable results, which often leads to the equipment being abandoned.

Capacitive, resistive, and even analogue microwave techniques have innate limitations. They can be susceptible to variations in free ions in the material and do not measure in a linear manner as the moisture changes. This results in an increasing loss of precision as the material becomes more wet.

Near Infra-Red (NIR) sensors are precise but more costly and require frequent servicing from external suppliers. Being an optical technology, they can only measure the surface of the material. However, they can additionally measure fat and protein content.

Hydronix offers a range of Digital Microwave Sensors which use a unique measurement technology which is linear at the point of measurement.

The sensors measure ‘into’ the material, offering very representative sampling and this measurement is not affected by free-ions (such as salt).

All sensors are temperature tested in production to ensure they operate linearly at all temperatures and then factory-calibrated to have identical measurement characteristics.

This simplifies the installation and use of multiple sensors, and once installed and calibrated, they are virtually maintenance-free.

Hydronix has been continually developing microwave sensors for over 40 years, operates globally and has excellent service and support capability.

  1. 25 Shocking Facts About Food Waste (28th September 2023), Earth.Org. s ↩︎

Neal Cass

Neal Cass

After gaining his degree in Electronic Engineering from the University of Southampton in England, Neal spent 10 years developing and commissioning control systems for a major international food process system manufacturer. In 2007 he started working for Hydronix as a Customer Service and Software Development Engineer before becoming Sales Manager in 2011.
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