Fouling from Dairy and Plant-Based Beverages: Comparison of Chemical and Enzymatic Cleaning

Abstract

Fouling is a major problem during heat treatment of dairy and plant-based beverages, leading to increased cleaning demand and production downtime. Conventional cleaning methods rely on chemical detergents (acids and bases), which raise sustainability concerns. A potential cleaning option is the use of enzymes, which has a lower environmental impact.

Plant-based dairy alternatives are increasing in popularity and differ in composition and processing from traditional dairy, yet research on their fouling and cleaning remains limited. Therefore, this study aimed to investigate differences in the quantity and composition of fouling from milk, whey, and oat drink, and explore the possibility of using enzymatic rather than chemical cleaning.

Fouling and cleaning experiments were performed at laboratory scale using a Quartz Crystal Microbalance with Dissipation monitoring (QCM-D) with stainless steel covered sensors to simulate a heat exchanger surface. Fouling deposits were characterized using optical microscopy and Scanning Electron Microscopy (SEM) with Energy-Dispersive X-ray spectroscopy (EDS). Whey protein fouling was further investigated at pilot-scale using a cleaning-in-place (CIP) setup.

It was observed that oat drink generated the greatest amount of fouling, followed by whey, which had marginally more fouling than milk. Milk and whey fouling consisted predominantly of proteins, with some minerals, where more minerals were detected in milk than in whey. In contrast, oat drink fouling was primarily composed of minerals, with fewer proteins. Protease was the only enzyme that provided a cleaning effect, and the optimal enzyme concentration was determined to be 0.5% (v/v) for milk and 0.05% (v/v) for both whey and oat drink.

The enzymatic cleaning outperformed alkaline cleaning for all products. For milk fouling, acid cleaning performed similarly to enzymatic cleaning, but enzymatic cleaning yielded slightly better results, with no additional benefit from combining them. For whey fouling, the cleanest result was obtained with enzymatic cleaning alone, whereas the combination of enzymatic and acid cleaning was most effective for oat drink fouling. For pilot-scale testing of whey fouling, chemical cleaning performed better than enzymatic cleaning.

In conclusion, enzymatic cleaning performed comparably or better than chemical cleaning at laboratory scale. Although further testing and optimization are required for upscaling, the findings show that enzymatic cleaning is a promising approach for more sustainable fouling removal in dairy and plant-based beverage applications.

Abstract (Swedish)

Bildandet av beläggningar på värmeväxlarytor (fouling) är ett stort problem vid värmebehandling av mejeriprodukter och växtbaserade drycker, eftersom det leder till ökat rengöringsbehov och stopp i produktionen. Konventionell rengöring använder kemiska rengöringsmedel (syra och bas), vilket har en negativ miljöpåverkan. Ett potentiellt alternativ till detta är den mer miljövänliga enzymatiska rengöringen.

Konsumtionen av växtbaserade mejerialternativ ökar och trots att dessa produkter skiljer sig från traditionella mejeriprodukter både gällande sammansättning och tillverkningsprocess så är kunskapen om skillnader i fouling och rengöring begränsad. Syftet med detta examensarbete var därför att undersöka skillnader i mängd och sammansättning av fouling från mjölk, vassle och havredryck, samt att utvärdera möjligheten att ersätta kemisk rengöring med enzymatisk rengöring för borttagning av fouling.

Fouling- och rengöringstester genomfördes i laboratorieskala med hjälp av kvartskristallmikrobalans med dissipationsmätning (QCM-D), där sensorer med en yta av rostfritt stål användes för att efterlikna en värmeväxlaryta. Resultaten analyserades med optisk mikroskopi samt svepelektronmikroskopi med energidispersiv röntgenspektroskopi (SEM-EDS). Rengöring av fouling från vassle undersöktes även i pilotskala med hjälp av en cleaning-in-place (CIP)-uppställning.

Resultaten visade att havredryck gav upphov till störst mängd fouling, följt av vassle som hade marginellt mer fouling än mjölk. Fouling från mjölk och vassle bestod främst av protein med inslag av mineraler, där fler mineraler detekterades i mjölk än i vassle. För havredryck dominerade istället mineraler, med mindre inslag av protein. Proteas var det enda enzymet med en rengörande effekt och de optimala koncentrationerna bestämdes till 0,5% (v/v) för mjölk och 0,05% (v/v) för både vassle och havredryck.

Enzymatisk rengöring gav bättre resultat än alkalisk rengöring för samtliga produkter. För mjölk var syrarengöring jämförbar med enzymatisk rengöring, men den enzymatiska rengöringen gav något bättre resultat och att kombinera dem medförde ingen ytterligare förbättring. För vassle fungerade enzymatisk rengöring bäst, medan en kombination av enzym och syra var mest effektiv för havredryck. För test med vasslefouling i pilotskala fungerade kemisk rengöring bättre än enzymatisk rengöring.

Sammanfattningsvis visar resultaten att enzymatisk rengöring gav likvärdiga eller bättre resultat än kemisk rengöring i laboratorieskala. Trots att ytterligare testning och optimering krävs för att kunna skala upp enzymatisk rengöring visar resultaten att metoden har stor potential som ett mer hållbart alternativ för rengöring av fouling i mejeri- och växtbaserade dryckesapplikationer.

Popular Abstract

Have you ever heated milk in a saucepan and accidentally burned it, so it stuck to the bottom of the pan and then had to spend lots of time cleaning it? This does not only happen in our kitchens at home but also at the dairies. However, this heating process is very important to kill harmful bacteria to make the milk safe to drink before it enters the supermarket. The burnt deposits that stick to the heat-treatment equipment is called fouling and fouling gives rise to the need for a lot of cleaning. The biggest part of production costs in the dairy industry is actually spent on cleaning!

This study explored whether the cleaning of dairy processing equipment to remove fouling can be performed in a more sustainable way than it is today. The common method is to use chemicals, and the more sustainable option would be to use enzymes. Enzymes are proteins that occur naturally in living organisms. For example, they can break down molecules found in milk such as proteins or fat. It was found that enzymes work for removing fouling from milk and whey powder solution. Whey protein is the component of milk that contributes the most to fouling formation. Surprisingly, enzyme cleaning worked better than chemical cleaning in the laboratory, even with very small amounts of enzymes. Enzymes are more sustainable because they give rise to less chemical waste and can be operated under milder conditions than the chemicals. However, enzymes are targeting specific compounds, and it is important to know what the fouling consists of to select the correct enzymes for cleaning.

With a growing population and limited natural resources, it is important to have effective and sustainable food production. Oat drink has become a popular alternative to milk that is considered more sustainable. It was tested whether fouling from oat drink production could be cleaned using enzymes. The results showed that enzymes worked partially, but it was also found that oat drink generates more fouling than milk and whey. There is limited information about fouling from plant-based dairy alternatives but hopefully these findings can contribute to a more sustainable production process of an already sustainable product.

Implementing enzymatic cleaning to replace parts of the chemical cleaning is beneficial both for the environment and for the companies that can save energy and costs. With further research, enzymatic cleaning may not only be applied in dairy and plant-based beverage industries, but it could be the standard in food processing plants.

• author: Messering, Nellie and Sommerland, Lovisa
• supervisor: Olga Santos
• organization: Pharmaceutical Technology (master); Food Technology and Nutrition (M.Sc.)
• course: KLTM06 20261
• year: 2026
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: QCM-D, Fouling, Oat drink, Whey protein, Milk, SEM-EDS, Enzymatic cleaning, Dairy processing, Food engineering nutrition and food chemistry
• language: English
• id: 9236784
• date added to LUP: 2026-06-16 13:59:23
• date last changed: 2026-06-16 13:59:23