In this chapter I will be asking How will the introduction of inline Process analysis support the Brewing and cellars operations in respect to productivity?
3.1 Raw Material Receipt
During grain receipt, the delivery vehicle is weighed in and after offloading it is weighed out before it exits the Brewery to ensure that the correct quantity ordered is delivered. It is vital to routinely check that the raw material consignment batch ordered is within allowed specification; hence the raw materials are randomly checked for quality specifications. E.g. Malt is checked for moisture content since the Brewer is paying for exact not water.
In most Breweries, Sampling of malt is done with spears. The spears are hollow spikes inserted into the grain bed to retrieve a sample of the grains. These samples are randomly collected to ensure homogeneity in the analyzed batch of malt. In modern Breweries, a more refined system is used using a diverter system. This equipment either continuously takes small samples or occasionally diverts samples into a sample collection chamber as the grains are transported through the conveyor system to the grain silos.
Analysis of the sample is done in the Laboratory for the following parameters:
Foreign matter e.g. insects, mould, stones, dust etc.
Contaminants e.g. oil etc.
Grain moisture content analysis is important as a high moisture content > 10% will lead to the following problems:
Encourage pest growth like insects, moulds, fungi and bacteria
Alter the biochemical structure of the grains
Hence a thorough analysis of these parameters at grain intake is important to prevent problems downstream in the production process. Other possible problems that might arise from a poorly modified batch of malt include:
Poor extract recovery leading to low Brewhouse yield
sticky spent grains resulting in difficulties in discharging the spent grains from the filtration system
Viscous wort- resulting in fermentation problems
Poor wort separation & poor clarification performance- leading to reduced Brewhouse productivity
Potential carbohydrate haze- Leading to beer stability problems
3.1.1 Analysis in Storage
Once the raw material has been received into the silo, other critical parameters that are regularly checked are:
1. Temperature: e.g. Raw materials like sucrose must be stored at 45oC to prevent crystallization. The temperature of raw grains must be regularly checked to prevent isolated hot spots which might lead to grain spoilage.
2. Humidity: High humidity coupled with high temperature promotes microbial growth which affects the raw material quality.
Below in table 1 is a summary of all analysis done during raw material intake and storage
S/N Analysis type Location Analysis done/ Method
1 Malt quantity in Silo Graduated deep stick/ rope system (Online)
2 Grain truck Online (Weigh Bridge)
3 Grain moisture Content Laboratory (Oven Method)
4 Silo Temperature Online (Hand held Thermometer)
5 Relative Humidity Online (Hand held Hygrometer)
6 Extract Content Laboratory
7 Physical inspection Laboratory & Online
Table 1: Analytical parameters checked on receiving grains
Possible installation for inline Process equipment on the Malt intake and Storage system
With the availability of hand held moisture meters, this technology can be adapted for inline measurement.
Fig 1 below is a schematic diagram of the grain intake system with imbedded in-line analytical process meters
Fig.1 Malt intake system with inline analytical equipment
One of the main raw material used in Beer production is Malt because, it contains all the essential ingredients. The Malt and other adjuncts like maize/Sorghum are milled to produce grist (cereal flour). The main objectives for milling are:
Reduction of Particle size
Control of particle size
The grains are crushed to ensure the highest possible yield of soluble nutrients during mashing. Depending on the filtration method e.g. Lauter tun, care must be taken not to completely disintegrate the husk as it might reinforce the filter bed during wort filtration. However, it does not matter much if a mash filter is used, as it uses porous polypropylene cloths that acts as the filter medium.
3.1.3 Grist Evaluation
It is essential for the Brewer to check the particle size distribution from time to time to determine the integrity of the mill and to preempt Brewhouse problems (The Institute of Brewing and Distilling ,2008). In many Breweries, grist samples are collected during milling and analyzed in the Laboratory using an equipment called Plansifter. The Plansifter consists of a series of five sieves stacked as columns through which a sample of the grist is shaken. The five sieves separate the grist into six fractions which are:
Fine Grit 2
Proposal: To explore the possibility of integrating this sifter into milling system for inline measurement during grain milling.
3.2 Brewing Process Diagram
The Brewing process flow diagram is represented in Fig. 2 below:
Fig 2. Process flow diagram of the Brewing and Wort Cooling Process
Mashing: In this process, the grist is suspended in water and heated to prepare an aqueous extract from the grist in the presence of an appropriate combination of pH, temperature and ions. The aim of mashing is to convert as much of the starch and protein into fermentable extract that can be fermented by the yeast. This process is mostly carried out by malt enzymes. Individual enzymes in the mash have optimal working temperatures and above these temperatures they are quickly denatured.
There are generally two types of Mashing regimes followed by Brewers these are:
Infusion Mashing Process
This method utilizes a single temperature regime usually 65oC. It is employed for highly modified wort which allows the appropriate formation of both adequate fermentable sugar and total soluble nitrogen.
Decoction Mashing Process
Used for less well-modified wort. In this case, a relatively low initial temperature is used to promote proteolysis followed by a higher temperature for starch gelatinization and amylolytic attack. Successive portions of the mash (part mash) are removed and boiled then returned to increase gradually the temperature of the main mash. This process is depicted in fig 3 below.
Fig 3: Decoction Mashing process diagram showing all the different temperature rests
Temperature programmed mashing
In this method, the temperature is gradually increased in a series of steps to allow progressive enzymic degradation of proteins and carbohydrates. It is illustrated in fig. 4 below
Fig. 4: An example of a temperature programmed mashing
Since the mashing process is very highly dependent, there are critical environmental factors that needs to be carefully monitored to optimize the process.
1) Temperature: it affects mashing mainly by influencing enzyme activity which determines starch gelatinization, hydrolysis and dissolution.
2) pH has a major influence on the mashing process and in particular enzyme activity. Table 2 below shows the optimum pH of various enzymes. However, the optimum pH for an infusion mash is 5.2-5.5. If this pH is used, the following will result:
More rapid amylolytic starch degradation
Enhanced carboxypeptidase and protease activity
Altered protein solubility and coagulability
Minimal tannin extraction.
3) Grist to water ratio- is described as the proportion of malt grist mixed with hot liquor to generate mash. Imagine a ton of malt held in a grist case above the mash tun overnight ready for mashing the next day. Adding this cool malt to the hot liquor will result in the mash having a cooler temperature than the liquid added as the two mixes and the temperature equilibrates. Hence it is important to determine the ambient temperature of the grist before it is mixed with the water. The hot process water temperature determines the strike temperature.
4) Mash Thickness- table 2 below, shows that individual enzymes in the mash and their optimal working temperature. Hence the thickness of the mash determines the extent to which the malt enzymes remain active. Dilute mashes encourage more rapid enzymatic hydrolysis because reaction products are less concentrated and therefore enzyme inhibition is reduced. Thick mashes protect heat labile enzymes from denaturation.
From the above, during brewing the following parameters and analysis are extremely important as they influence enzyme activities which determines the final beer product quality.
Table 2. Optimum Conditions & Activation Temperatures for various enzymes during mashing
Table 2 optimum conditions and activation temperatures of carious mashing enzymes (Wainwright, T., Basic Brewing Science, 1998)
The most important enzymes among the lot in Table 2 above are the ? & ?- amylases. They convert the remaining unmodified starch granules in the mash into fermentable sugars.
The Brewing process is sub-divided into six processes which are:
Protein Rest: Malt proteins are solubilized during mashing depending on the temperature and pH. However, malt protease is heat labile and thus more protein solubilization occurs during malting than mashing. Lower mash temperature favors greater concentrations of wort total soluble nitrogen. The lower the mash temperature, the greater the proportion of total soluble nitrogen arising as free ?-amino nitrogen (FAN). The mashing temperature at 50-55oC favor high ?-amino Nitrogen.
Gelatinization: The process in which the starch granules are exposed to enzymic attack. The elevated temperatures during mashing gelatinizes the starch granules (disrupts their crystalline structure) making them susceptible to enzymic attacks (? and ?-amylases) which are present in the malt. ?-amylases are much heat labile and it activity does not persist for long at high temperatures. Limit dextrinases are also heat labile and are rapidly denatured. The optimum pH for amylase activity is around pH 5.3 (Boulton & Quain, 2001, p.38). Thus, it is important to monitor and control the temperature and the pH during mashing-in.
Saccharification: There are two enzymes responsible for starch hydrolysis; these are: ? -amylases /liquefying enzymes characterized by reduction of wort viscosity and ?-amylases (Saccharifying enzymes). ? -amylase is an endo enzyme that degrades starch from within the molecule. It opens the large starch molecules. It can cause an extremely rapid decrease in molecular size of the starch polymer, dramatically decreasing the viscosity of the starch solution. It is due to this it is called liquefying enzymes. ?-amylase is an enzyme that sequentially hydrolyses the starch molecules, releasing glucose from that point along the chain.
During the Mashing process in most Breweries, critical parameters like mash temperature are checked inline while pH and Saccharification test are either checked online or in the Laboratory after mash samples are collected, cooled to 20oC. The process is not allowed to proceed until confirmatory results are obtained which usually takes between 5-10 mins at best hence prolonging the Brewing cycle time. Once a confirmatory test using iodine solution is obtained denoted by yellow coloration it is heated up to 78oC which is the mash-off to denature the saccharifying enzymes. Hence fixing the sugar composition.
3.2.1. Critical Brew House monitoring Parameter
1. Temperature- Grist, Process water, Mash
2. pH- Mash pH
3. Time- mashing in time, time for the various rests (protein, gelatinization, Saccharification etc.)
4. Saccharification- Starch Conversion to simple sugars
5. Volume- Process water, Mash
6. Weight- Raw material
In most Breweries, these parameters are either checked in the laboratory (pH, Saccharification) or online. Only few of these parameters are checked inline (Temperature &Time). In the future, it is expected that these measuring parameters will be done in-line with the aid of inline process analysis equipment after mashing plant modification which is represented schematically in Fig. 5 below.
Now, in Breweries VDK concentration in fermenting wort/beer is measured in the Laboratory by either using Spectroscopy or Gas chromatogram. This measurement is done daily especially when fermentation enters the secondary phase. It is so critical that it determines fermentation temperature control and the duration yeast can stay in the beer as early yeast removal, ensures very high VDK concentration and late removal leaves the VDK levels to almost undetectable levels in the beer. Hence, VDK determines the utilization rate of fermentation tank and overall cellars productivity.
Fig. 5: A schematic diagram of a mashing system.
3.2.2 Wort Filtration
Is the process of separating the sweet wort from the malt spent grains. The converted sugars are carefully leached out from the Mash and transported either to the holding vessel for temporary storage or delivered directly into the wort copper. This process continues until the wort concentration (run-off) falls to a value at which further treatment is uneconomical. The critical analytical parameters checked in this stage are:
? Wort gravity (both strong wort and last running). Wort gravity determines the extent to which sugars from the mash can be extracted. It also determines the time of wort boiling as too low gravities requires extended boiling times for wort concentration which has both energy usage and quality implications. Extended boiling times contributes to color formation due to mallard reaction. Wort color determines the final color of the beer. At the moment, wort gravity is either determined in the Lab or online after sample collection and analysis at 20oC.
? Wort turbidity (throughout the filtration process). This parameter is critical as too high wort turbidity (>??? ) has two implications (1) extraction of polyphenols from the husks which subsequently leads to stability problems in the final beer, (2) trub carry over which get stuck to the heating surface of the wort copper affecting heat transfer leading to extended boiling times and high energy utilization. The trub might also affect yeast cell performance by binding to the yeast surface forming flocs which causes the yeast cells to quickly settle to the bottom of the tank hence causing fermentation problems. Wort turbidity and wort residual sludge are determined in the Lab using a density meter and Imhoff cone respectively.
? Wort pH: The target pH of wort after boiling is (5.1-5.3). It is believed this pH range,
? Temperature of sparge water (temperatures above 78oC will leach out tannis from the husk that cause flavor and stability problems; temperatures below 76oC will be ineffective in leaching out the extract from the grains)
3.2.3 Wort Boiling
Clarified sweet wort delivered to the copper (kettle)is subjected to heat treatment. In beers subjected to the Reinheitsgebot laws, only hops are added to an all-malt sweet wort and boiled. In other countries additional sources of fermentable sugar in the form of liquid syrup adjuncts may be added with the sweet wort.
Wort boiling serves the following functions:
1) Wort sterilization and malt enzymes inactivation