Traditionally, sausage skins were made from the small intestine of meat animals, especially pigs, but also sheep, cattle and goats. These so-called natural casings have been utilized for centuries, but in recent decades artificial casings have become popular in many markets. Artificial casings include collagen (often derived from animal skin), cellulose (from plant materials), plastic, and more recently alginate (from seaweed).

The growth in artificial casings has been prompted by a number of factors, including the high costs that result from the number of processes necessary to create the natural casing product. Also, natural casings tend to be variable in length, diameter and thickness, so it is more difficult to streamline sausage production, and the process incurs a heavier labour requirement. In contrast, continuous accurate monitoring of the artificial casing process removes the requirement for manual sampling and testing, and enhances both process efficiency and product uniformity.

Alginate casing

Alginate is found in the cell walls of brown algae which is a large group of multicellular algae, including many seaweeds located in colder Northern Hemisphere waters. An important feature of alginate is its ability to hold many times its own weight in water, making it a naturally gelling substance.

As a film-forming natural polymer, alginate can be used as a casing for sausages through its gel formation with calcium ions. During the production process, meat mixture is extruded to form the sausage, and a layer of sodium alginate is simultaneously applied (co-extruded) to the outer surface, before a calcium chloride brine solution is used to for dehydration and to induce gel formation. This creates a layer of calcium alginate film on the sausage, which provides the strength and flexibility required in a sausage casing.

The salt content in the brine solution is very important and needs to be closely monitored because it affects the color, texture and overall quality of the sausage. 

The main advantages of co-extrusion over natural casings are:

•    Lower purchase cost
•    Ideal for automation
•    Low labour requirement
•    Product consistency
•    Flexibility – can be used for many different types and size of sausages
•    Stored as alginate powder, so no refrigerated storage necessary
•    Speed and throughput
•    Suitable for vegetarian, vegan and Halal (if alginate)
 

Monitoring alginate brine with in-line refractometers

The brine solution is stored in a brine tank, and spent brine is recycled to this same tank. Consequently, the brine is constantly diluted by the moisture that is removed from the casing gel. It is therefore necessary to monitor the salt solution so that the correct amounts of salt can be added to the brine solution. This function is performed by the Vaisala refractometer which monitors the salt content in real-time. 

There are two possible locations for the refractometers; directly in the brine tank itself, and a second refractometer can be installed in the salt supply tank.

The Vaisala refractometer measures the refractive index (RI) of the liquid, which correlates directly with the salt concentration of the brine solution. In-line RI monitoring with automatic feedback control enables process operators to ensure consistent and reliable operations; thereby protecting product quality and reducing downtime.  In contrast with many other liquid concentration methods, the Vaisala refractometer is extremely accurate and reliable and needs no regular maintenance. Importantly, these refractometers are not affected by particles, bubbles, crystals or color, so they can be employed in a wide variety of solutions for measuring liquid concentration. The Vaisala K-PATENTS refractometers are also 3-A Sanitary Standards and EHEDG certified, which is essential for food processing equipment.

The refractometers produce mA and Ethernet output signals that allow automatic operation of the process. Moreover, the refractometers can be calibrated to read the concentration of NaOH in g/L, wt-% or any other engineering unit preferred by the factory.

Co-extrusion with collagen gel

In addition to alginate gel, it is also possible to use collagen gels in sausage manufacture. Collagen casing is largely derived from beef and pig hides, but it offers most of the speed and efficiency advantages presented by alginate gels.

After co-extrusion with collagen gel, sausages are passed through a brine solution in a similar manner to the alginate gel process. Vaisala refractometers are able to continuously monitor the process as outlined above, to ensure that the correct salt concentration is maintained and product quality is protected.

Emphasizing the importance of the brine measurement, a sausage manufacturer in the USA said: “We treat co-extruded sausage casing with dipotassium phosphate to control the moisture, which directly affects the color and texture of the final product. Too much moisture in the casing makes the sausage too dark and the texture too chewy, while too little means the sausage will be too light and the texture too soft. The Vaisala K-PATENTS® refractometer helps to keep the moisture at the specified level, ensuring a standardized end product.”

Cellulose sausage casing

Vaisala refractometers are also used in cellulose sausage casing processes. In this application a cellulose fiber cloth is used to create the sausage casing, but first the cloth is desulfurized by passing it through a Sodium Hydroxide (NaOH) bath. Also known as caustic soda, this solution is supplied from a tank, and spent caustic is returned to this tank. Consequently, the NaOH concentration needs to be replenished because caustic is lost in the cloth during the impregnation process. A Vaisala refractometer is therefore employed, in a similar manner to the alginate and collagen applications above, to continuously monitor (in this case) the NaOH concentration and ensure accurate replenishment.

Summary

In-line refractometry is the ideal technology for controlling the artificial sausage casing process. By providing continuous data, refractometers enable sausage manufacturers to control many of the key product quality features. 

Unaffected by particles, bubbles or color, the same technology is used for monitoring liquids in a wide range of other industries including semiconductor, chemical and refining, pulp and paper, textiles, pharmaceutical, brewing, beverages and of course food.

The popularity of cellulose and alginate casings is growing as manufacturers look for ways to lower costs, expand production and improve consistency whilst improving product quality, process efficiency, speed and flexibility. However, in order to take advantage of these benefits it is necessary to be able to continuously measure process liquids with a technology that is accurate, reliable and able to operate in challenging conditions. The Vaisala K-PATENTS refractometers meet that requirement and therefore help to meet the world’s growing passion for high quality sausages.

You might also like to read about the in-line refractometer technology and other solutions by Vaisala for food and beverages industry.
 

Every day we hear global politicians saying that their decisions are “led by science” and the public is increasingly aware of the ways in which science affects all walks of life. In the following article we will focus on how science is driving the food and beverage industry, and in particular, how Vaisala’s technologies are helping to optimize sustainable food production.

It’s easy to understand that art plays an important role in the food and beverage industry; creativity and imagination are essential in packaging and advertising, as well as in product development. At Vaisala, however, we believe that science plays the dominant role: development of measurement technologies; helping with product formulation; optimizing processes; protecting safety; ensuring quality; enabling product consistency; and empowering sustainability. Looking forward, how will science help the industry overcome its latest challenges?

The challenges

According to the FAO (1), nearly one in three people in the world (2.37 billion) did not have access to adequate food in 2020. The worst affected countries were in Africa and Asia – and at a time when the main food-related challenges in some countries were obesity and food waste. Food security, nutrition and accessibility all present growing challenges.

Water scarcity can be defined as insufficient fresh water to meet normal requirements. It can be caused by climate change (drought), water contamination, excessive or inefficient water use, or by insufficient or failing water infrastructure. According to the United Nations (2), without adaptive measures, the number of people who lack sufficient water for at least one month per year will soar from 3.6 billion today to more than 5 billion by 2050. Again, there is a growing pressure for better efficiency and less waste.

Climate change is threatening crops which can be wiped out by drought, floods, hurricanes etc. According to the UN Office for Disaster Risk Reduction (3), climate-related disasters have almost doubled compared to the previous 20 years. Greater resilience is therefore required in our agricultural systems.

A limited shelf-life for many products imposes extra risk for the food and beverage industry, and makes it more vulnerable to supply chain problems. Therefore, there is a strong demand for measures to improve resilience and protect business continuity. Coupled with cost and sustainability issues, supply chains need to be short, fast, safe, and traceable. As well as sustainable products, consumers are also looking for better packaging, with less reliance on plastics.

Consumer demand for safe, healthy, nutritious food continues to grow.  Manufacturers are therefore under growing pressure to provide better information on labelling; especially for ingredients with health considerations such as sugar, salt, and calorific content. Consumers are also increasingly looking for products with a low carbon footprint, and this is driving the growth in meat alternatives, for example. Carbon footprint information is being requested by retailers; frequently this now includes Scope 3 emissions, which are those that arise outside of their own operations.

With global energy and food prices soaring, food and beverage manufacturers are experiencing both environmental and financial pressures to improve energy efficiency, reduce waste and increase the use of renewable energy – wind, solar and biogas.

Science at Vaisala

Science is offering solutions to all the challenges outlined above, and Vaisala is actively involved in many of them. For example, Vaisala is the world’s leading manufacturer of meteorological equipment; enabling scientists to track climate change and extreme weather. In addition, Vaisala’s industrial measurement instruments enable better management of food and beverage processes, which:

• improves efficiency
• enhances and protects product consistency and quality
• reduces energy consumption
• reduces waste
• lowers costs
• improves the sustainability of the industry and helps in the fight against climate change

Vaisala technologies are employed extensively in the food and beverage industry, and many examples are given below, but in comparison with Vaisala’s global reputation in the meteorological business, the company is less well known – and may be one of the food and beverage industry’s best kept secrets, but most powerful assets.

The Vaisala brand is dictated by the company’s mission to provide observations for a better world through innovation that is driven by four key values:

1. Customer focus – providing measurement solutions to meet customers' needs
2. Pioneering innovation – curiosity driving continuous improvement
3. Collaboration – with partners, stakeholders and the global scientific community
4. Integrity – honesty, diversity, respect, reliability and sustainability

In the food and beverage industry, Vaisala products are utilized at every stage of the value chain; from agriculture, to processing, to storage, to distribution, to retail, and to waste management.

Vaisala technologies

With accuracy and long-term reliability as pre-requisites in all Vaisala development programs, the company’s products have established an enviable worldwide reputation, and now boast installations on more than one planet! Humidity and pressure sensors from Vaisala are currently operating in every continent on Earth, as well as on Mars in NASA’s Curiosity and Perseverance rovers.

Relative Humidity (RH)

Some of Vaisala's core technologies include measurement methods that are commonly regarded as industry standards. For example, humidity is one of the most common measurements undertaken in almost every industry. In 1973 Vaisala developed the world’s first thin-film polymer-based capacitive humidity sensor, HUMICAP®, which dramatically improved the accuracy and reliability of measurements, with major advantages including long-term stability and insensitivity to condensation, dirt and most chemicals. As a consequence, Vaisala humidity probes are routinely employed in food processes such as drying, cooking, baking etc. The applications for humidity measurements are almost endless; partly because excessive moisture in food can cause spoilage.

Carbon Dioxide (CO2)

Carbon dioxide is used by plants to grow by photosynthesis, so it is common practice for horticulturists to raise greenhouse CO2 levels to boost production. CO2 is also used in carbonated beverages and in the manufacturing facilities of perishable foods, and all of these processes require tight control, so they are ideal applications for Vaisala’s sensor technology.

The Vaisala CARBOCAP® carbon dioxide sensor features an innovative micro-machined, electrically tunable Fabry-Perot Interferometer (FPI) filter which enables a reference measurement that compensates for any potential changes in light source intensity, as well as for contamination or dirt accumulation in the optical path. Consequently, the CARBOCAP® sensor is highly stable over time, which means that operators do not have to worry about calibration drift or sensor failure.

Refractometry

Refractometry is a well-known method for measuring sugar content in products such as beverages and fruit products, but the inline Vaisala Polaris™ Sanitary Refractometers are routinely utilized in countless food and beverage applications for process monitoring and control. For example, Brix and dry solids measurement are widely used in food and beverage production processes.

In contrast with many other liquid concentration methods, the Vaisala refractometer is not affected by particles, bubbles, crystals or color, so these instruments can be employed in a wide variety of solutions for liquid identification and for monitoring the concentration of components. Importantly, the Vaisala refractometer is EHEDG and 3-A certified - these sanitary Standards protect hygiene in the production and processing of food.

Application examples for Vaisala in-line refractometers are given in the table opposite, but their versatility is demonstrated clearly by their involvement in every stage of the beer brewing process:

1. Mashing - measuring the concentration of the mash in water at the outlet pipe.
2. Lautering - measuring concentration to detect the appropriate shut-off point for rinsing.
3. Wort Boiling - continuous measurements of wort strength/gravity allowing the brewer to determine exactly when the wort has reached the required strength.
4. Whirlpooling – monitoring before and/or after the whirlpool to ensure that solids are removed quickly and effectively to produce a clear, bitter wort.
5. Cooling - ensuring that the bitter wort contains the correct level of dissolved solids before fermentation.
6. Fermentation - providing brewers with real-time insights into the process, and allowing them to accurately determine when fermentation is complete.
7. Filtration and maturation – quality control during the removal of yeast.
8. Filling and CIP - continuous monitoring of the filling and CIP processes enables automation, reduces wastage and lowers costs and energy use.

Biogas

Globally, there is an enormous focus on renewable energy and greenhouse gas emissions reduction, as countries and organizations seek to achieve Net Zero. Biogas offers an opportunity to utilize waste products from agriculture and food production, and also displace fossil fuels as an energy source. In addition, biogas processes produce digestate, which is a nutrient-rich fertilizer that can complete the circular economy in food production. In addition, biogas can generate electricity for use domestically and on farms.

Vaisala has developed technology to enable biogas process optimization. Uniquely, Vaisala’s multigas probes are able to monitor biogas inline and in real-time, which allows operators to improve the quality of biogas, lower costs and improve process efficiency. This final example demonstrates how Vaisala is involved in every stage of the food cycle, from food production all the way through to the anaerobic digestion of food waste.

Summary

Science can be defined as the pursuit and application of knowledge and understanding, following a systematic methodology based on evidence. At Vaisala, food is all about the science; measurement data from our instruments inform decisions and enable efficiency optimization. Science at Vaisala is driven by curiosity; with 14% of net sales invested in research and development, the company has a longstanding commitment to innovation. The food and beverage Industry has benefited enormously from the technologies that Vaisala has already developed, but for the company’s scientists, the greater source of excitement is the technology that has yet to be unveiled...

References

1. The State of Food Security & Nutrition in the World 2021. Food & Agriculture Organization of the United Nations: https://www.fao.org/state-of-food-security-nutrition/en
2. UN: Adaptation to Climate Change www.un.org/en/climatechange/science/key-findings#physical-science
3. United Nations Office for Disaster Risk Reduction, Policy brief: Disaster risk reduction and climate change. www.undrr.org/publication/policy-brief-disaster-risk-reduction-and-climate-change
4. Riddell et al. (October, 2020) The effect of temperature on persistence of SARS-CoV-2 on common surfaces. Virology Journal. https://virologyj.biomedcentral.com/articles/10.1186/s12985-020-01418-7
5. Meat plants—a new front line in the covid-19 pandemic. (July 2020) British Medical Journal. https://www.bmj.com/content/bmj/370/bmj.m2716.full.pdf

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Brewers will often attribute their success to passion, determination, and innovation, but once a beer has been developed and branded, it’s all about consistency. Process monitoring, therefore, has a key role to play. In the following article, we explain how in-line refractometers, located strategically at every stage of the brewing process, enable process optimization, save energy, reduce waste, lower costs and help deliver top-quality beer.

Sampling vs Continuous monitoring
Some breweries rely on manual sampling and laboratory analysis, but there are a number of significant disadvantages with this approach, so there is an inevitable trend toward in-line monitoring and increased automation. 

Laboratory analysis is obviously an essential component of research and development; providing an insight into the effects of different raw materials or processes on characteristics such as flavour and aroma. Laboratory analysis also plays an important role in investigatory work; helping to understand the chemistry. However, from a production perspective, sampling and analysis can be of limited value because of the cost and the delay incurred – by the time a lab result uncovers a problem; a significant volume of the product may have already passed through the brewery. Similarly, samples represent a ‘snapshot’ of the process at one moment in time, and are therefore unable to support feedback control or provide timely alarms, and are less able to uncover trends.

Monitoring technology
Vaisala’s K-PATENTS® sanitary refractometers can be calibrated in Plato, Brix, Balling, gravity, or density, depending on the preference of the brewery. They are available with 3-A Sanitary and EHEDG certifications and are designed to withstand CIP/SIP cleaning and rinsing procedures.

A number of different technologies have been employed to monitor various aspects of the brewing process, but some methods such as turbidity and density can experience measurement errors from fouling and interference by the larger suspended particles (especially in mashing and the lauter tun) and by the bubbles and foam that are present in most stages. Refractive Index monitoring is therefore preferred, and the key advantage of the Vaisala refractometers is that they provide accurate measurements at every stage of the brewing process without suffering from these interferences.

A further advantage of refractometers is their speed of response, which is a particular advantage in the packing/filling line and CIP process – this will be discussed later.

Refractive Index (RI) measurements are based on the angle of refraction of light in the process medium, using an LED light source. A sensor continually detects the critical angle at which the total reflection of light commences, and the concentration of dissolved solids is calculated taking pre-defined process conditions into account. Vaisala’s sanitary refractometers are therefore supplied factory calibrated to meet the requirements of the specific brewery and are deployed at most stages of the brewing process, some of which are described below.

Mashing 
Typically, mashing takes place in a tun, which is an insulated brewing vessel with a false bottom. Malt is steeped in hot water which activates enzymes that cause starch in the malt to break down and release simple sugars, producing wort.

Mashing is a crucial step because it determines the final structure of the beer, so it is important to maintain a consistent wort output. The refractometer is used to measure the concentration of the mash in water at the outlet pipe. 

The process by which the grains are separated from the wort is known as lautering, which is often conducted in a separate chamber known as a lauter tun.

Lautering
Sparge water rinses the grains inside the lauter tun to complete the extraction of sugars, producing a clear wort with a concentration that gradually decreases during the rinsing. The refractometer continuously measures this concentration, allowing the detection of the appropriate shut-off point for rinsing, which prevents the excessive use of water and saves energy. 

Wort boiling
Once the sweet wort has been separated, it is pasteurized in a wort boiler or brew kettle, and this is the stage at which hops and other flavourings may be added. Wort boiling terminates enzymatic activity, preserves foam-positive proteins, evaporates unwanted flavour volatiles, and helps to form desirable taste and aroma compounds. It also brings the brew to the appropriate strength or gravity, so this is an extremely important stage in the brewing process.

The refractometer is installed directly in the wort boiler, providing continuous measurements of wort strength/gravity so that the brewer can determine exactly when the wort has reached the required strength. This improves beer quality and consistency while helping to optimize brewing time and energy consumption.

Whirlpooling
After boiling, the wort is transferred to a whirlpool, where solid particles (hop rests and coagulated proteins) are separated from the bitter wort. The whirlpool causes residual particles to coagulate and settle out of the liquid as a sludge known as trub, which is partially removed from the bottom of the kettle. It is important that the solids are removed quickly and effectively to produce a clear, bitter wort for transfer to the next stage, so a refractometer may be installed before and/or after the whirlpool.
 

Cooling
Once boiling is complete, the wort is cooled by a heat exchanger which recovers some of the energy used to boil the wort. Refractometers can be installed in the outlet of the cooler as a quality control measure; ensuring that the bitter wort contains the correct level of dissolved solids before fermentation. Alternatively, or additionally, a measurement can be made after the boiler and prior to the whirlpool, to avoid the possibility of processing bitter wort that does not meet the required specification.

Fermentation
During the fermentation process, yeast converts sugars and amino acids in the wort to carbon dioxide and alcohol. The gravity of the fermenting liquid is measured as the specific gravity, or relative density compared to water. In the brewing industry, this is mostly measured on the Plato scale, which is very similar to the Brix scale used by the wine industry.

Spent yeast collects at the bottom of the fermentation tank and is regularly removed, which helps to clarify the beer.

The density of the wort varies according to the sugar content, so the density readings decline as fermentation progresses. The alcohol percentage can be calculated from the difference between the original wort gravity and the current specific gravity. Refractometers are therefore able to closely follow the fermentation process; providing brewers with real-time insights into the process, and allowing them to accurately determine when fermentation is complete.

Filtration and maturation
Maturation includes all transformations between the end of primary fermentation and the removal of yeast from the beer. After fermentation, the beer is allowed to rest, so that any remaining spent yeast can settle out. However, a number of filtration techniques are often applied to further clarify the beer. This is the final opportunity to affect the quality profile of the beer – flavour, bitterness, odour and foam stability, clarity, color, alcohol, and gas content. All of which vary according to the requirement of the brand, so refractometers can fulfill a vital role in quality control.

Filling and CIP
When the beer is ready for distribution it is packed in bottles, cans, casks, and barrels which must be clean and sanitized. In addition, the internal surfaces of pipes, vessels, tanks, and packaging equipment must be cleaned between batches and between different products. Known as Clean in Place (CIP) this protects the beer products from microbiological and chemical contamination. In large modern breweries, the cleaning processes are complex, so automation is frequently utilized to improve speed and efficiency, and lower costs. 

At the filling line, the refractometer instantly detects the product-to-product and product-to-CIP cleaning interfaces, allowing efficient change-over between products or batches. The refractometer output signal can also be utilized for quality control monitoring, and to ensure correct product-to-packaging selection. The response speed of the refractometer means that the interfaces (between product/cleaning chemicals/water), can be detected very quickly, which avoids waste and ensures that no product contamination occurs.

Continuous monitoring of packing and CIP processes with the Vaisala refractometers, therefore, enables automation, reduces wastage, and lowers costs and energy use.  

Why use refractometers throughout the brewery?
In contrast with other methods, the main advantages of Vaisala’s refractometers are that they provide greater insight into every stage of the brewing process; they are not affected by suspended particles, bubbles, or color, and with the option of automatic prism wash with steam or high-pressure hot water, they are not affected by scaling or fouling.

Each Vaisala refractometer is factory calibrated for the full measurement range (e.g. 0-100 degree Plato), which means they can be freely interchanged between installation locations without parameter changes. Furthermore, the Vaisala refractometers do not require any routine recalibration or maintenance. 

In summary, it is certainly true that brewing success is underpinned by passion, determination, and innovation, but, with the help of refractometry, brewers can optimize their processes, reduce waste, lower energy consumption and rest assured that they will continue to produce consistently good quality beer.