BLT Stages

Abstract Bachelor Project 1 FBT 2020-2021: Characterization and treatment of blanching water used in the production of potato products

Due to the raising demand for potatoes and potato products as frozen fries and flakes much more water is needed. Therefore it’s much more needed to consume water smarter and more economically. Because the potato and vegetable processing industries are responsible for eighteen percent of the total water consumption in the food industry. The goal is to create more circular processes instead of the linear processes which are used these days to reduce water waste. In this study, several physical and chemical separation techniques as filtration, centrifuging, settle and coagulation/ flocculation are used to reduce the COD and turbidity in the blanching water as pre-treatment technologies for the membrane filtration technology used to purify the water from sugars and starch. The blanching step is one of the most water-consuming steps from the vegetable and potato production process. First, the blanching water was characterised to determine the composition and concentration of several parameters as COD, chloride, phosphate, nitrate, turbidity, conductivity, pH, glucose, starch, Kjeldahl nitrogen and dry mater. Secondly the filtration methods were performed on the blanching water. The treated blanching water was again characterised to see the impact of each purification method. Before it can be reused it must meet the water quality norms of drinking water. Out of the results, the best purification method is filtration with small pore size. This method is can meet three out of eleven norms. The other physical methods only meet two out of eleven. Coagulation/ flocculation is not able to meet one of the required norms. Due to the addition of Fe(Cl₃), the chloride concentration is increased. Also, the pH value drops because of the formation of HCl. The turbidity and the nitrate concentration increase due to the addition of a polymer. In future studies the methods can be tested on semi-industrial scale. Also, different coagulants and flocculants can be tested to reduce the negative effects of Fe(Cl₃) and the polymer.

Abstract Bachelor Project 2 FBT 2020-2021: Stabilization of potato trimmings by controlled fermentation with the use of enzymes

Potatoes are produced everywhere in the world, so it is no surprise these are one of the most produced crops. Beside the consumable food part of the vegetable, there are also a few by-streams like the potato trimmings. Those trimmings still contain interesting compounds like proteins with interesting qualities. The extraction of these proteins could be a huge gain for the potato processing industry and a big contribute to the circular economy. Due to the high-water content in the potato trimmings, it is difficult to preserve them. The aim of this study is to test if enzymes- and what enzyme stabilizes the fermentation of those trimmings best, so proteins can be extracted. Therefor enzymatic fermentation will be compared between themselves and with natural fermentation.

In the research two different enzymes are added, in two different concentrations, to three different batches of potato trimmings. Whereafter the samples are incubated at two temperatures for several weeks. The samples are tested for microbial activity and pH. The microbial growth is tested through determination of the colony forming units of Lactobacillus species, as it is an important criterion to control the fermentation. Likewise, the growth of yeasts and moulds is tested, for it is important to control the stabilization. Also, the protein concentration is measured at a specific time as it is important that this criterion lays as close as possible to the concentration in fresh potatoes, for it is the aim to extract the proteins.

For both enzymes and natural fermentation, at all conditions, the amount of Lactobacillus  increases followed by a reduction afterwards. When adding enzymes to the samples, the amount of Lactobacillus is higher compared with natural fermentation. In natural fermented samples the growth of Lactobacillus starts after one day of incubation and lasts two days. The pH reduces faster, and obtains similar values with the aid of enzymes compared with natural fermentation.

In the beginning of the fermentation there is a significant effect on growth between natural fermentation and the enzyme samples, after one week the growth in the samples with the enzymes increases. Yet there is one enzyme that shows less growth when added, in a small concentration, to the samples in both conditions in comparison with naturally fermented samples. Small differences in the true protein concentration were observed between the different sorts of fermentations. The protein concentrations of the fermented samples are mostly lower when compared to the fresh sample.

Stabilisation is only slightly better when adding enzyme one in a small concentration at a lower temperature. Taking into account the high costs of enzyme additions, it seems that enzyme additions are not the best option for stabilisation.  It would require further research to decide if the benefits outweigh the costs. After further analysis, a better conclusion on the use of enzyme one can be made

Abstract Bachelor Project 3 FBT 2020-2021:  Research of Listeria monocytogenes in the food industry

Listeriosis, a fatal disease for young, old, pregnant and immuno-suppressed people, is caused by Listeria monocytogenes. There is worldwide a mortality rate of 20 – 30 %. This may be due to the lack of hygiene from personnel in a factory and minimalistic cleaning and disinfection in factory environments, resulting in cross- or post contamination.

The focus of this bachelor thesis was to investigate the presence of Listeria monocytogenes by environmental sampling in the freezing tunnel in a potato processing company. The effect of cleaning and disinfection on the presence of Listeria monocytogenes was taken into account. The number of other bacteria or groups was also determined, as these may co-exist with Listeria monocytogenes in a biofilm.

The environmental samples were taken by swabbing from a potato processing environment in Ringers ¼ strength solution and half Fraser broth. The samples in half Fraser broth were put in the incubator to develop any Listeria monocytogenes. The samples in Ringers ¼ strength solution were utilised to detect Pseudomonas spp., E. coli, total coliforms, thermophiles, anaerobic spores, lactic acid bacteria, sulphite reducing Clostridia and Listeria monocytogenes. Listeria monocytogenes positive samples were confirmed through the xylose-and rhamnose test. Therefore five colonies were picked from a Petri plate with presumptive Listeria monocytogenes and inoculated each on a TSA plate. After growth on these plates, they were inoculated in Eppendorf tubes with peptone water with xylose or rhamnose. Listeria monocytogenes is rhamnose positive and xylose negative.

In this preliminary experiment about 40 % of the samples on different locations were Listeria monocytogenes positive, especially the refrigeration compartment, the entrance of the freezing tunnel and on/under the conveyor belt in the freezing tunnel. The staff, large brush and dustpan from the freezing tunnel may be the main cause of cross-contamination. The shoes of the staff always tested positive, in that way by walking in the factory they take Listeria monocytogenes with them and contaminate the whole floor of the factory.

Cleaning and disinfection is a very important procedure in the factory because micro-organisms can contaminate the food. There can be concluded that the cleaning and disinfection is not as effective as it should be. Sure, some bacteria’s are reduced or completely gone, but others have a large number that may contaminate the food, this should be further investigated. Actions towards contaminations sources and hygienic design may be in addition to the cleaning and disinfection in order to reduce or prevent Listeria monocytogenes.

Abstract Bachelor Project 1 FBT 2019-2020:  Characterisation of blanching water from the potato processing industry

Potatoes are a very versatile product when it comes to food processing. Blanching is a very important step in the processing of potatoes as it reduces bacteria, inactivates enzymes, and eliminates reducing sugars from the potatoes, which results in a safer, high-quality product with a longer shelf life. However, this blanching process requires a lot of water and energy (to heat the water). Given the scarcity of water, a project on blanching water treatment (Sucr’eau) is started that allows the warm water to be reused and thus resulting in saving water and probably energy. This thesis focuses on the characterisation of samples from different potato processing plants to get a general idea of the composition of the blanching water quality to be able to determine the correct water treatment technology(ies). The determined parameters include pH, turbidity, conductivity, viscosity, chemical, and biological oxygen demand, sedimentation, dry residue, ash residue, phosphates, nitrates, chlorides, hardness, Kjeldahl nitrogen, sugars (mainly glucose) and starch. Unfortunately, due to the Covid-19 pandemic there are only a few preliminary results to discuss and very limited conclusions to be made. It is noticeable however that the blanching water from the first blancher from the process is generally the most contaminated one with higher values of COD, BOD, glucose, starch among other things.

Abstract Bachelor Project 2 FBT 2019-2020: Stability of probiotic fruit juice during storage

Uganda annually produces more than 42,000 tons of mangoes and watermelons. After harvest, about 35% of the fruit is bad because of spoilage. One of the possibilities to limit this loss is the transformation of the quickly perishable products into products with an increased shelf life, such as probiotic fruit juices. During this project only mango juice was used.

To know if the probiotics increase the shelf life of the mango juice, the stability of it needs to be tested during the storage.

The mango juice was inoculated with three bacteria strains (L. brevis, L. casei and P. pentosus) and fermented for 24 hours, followed by storage at 4 °C during 21 days. The following techniques were executed on the samples: microbiology (probiotics, any contaminating microorganisms), physiochemical properties (pH, titratable acidity, brix) and total phenolic compounds and antioxidant capacity (TPC, ABTS, DPPH). The tests were performed weekly.

The results showed that the three strains can survive in the mango juice as a matrix. Most of the present bacteria in the juice were probably lactic acid bacteria (PCA and MRS media results). The pH of the juice decreased because of the production of lactic acid. The results of brix showed an increase of soluable solids (control and P.pentosus) and a decrease for L.casei and L.brevis at first, but afterwards an increase. DPPH showed the same amount of antioxidants in the juice, ABTS showed the increase of antioxidants and TPC showed the decrease of total phenolic content.

The three strains exhibited a good probiotics characteristic, but it would be interesting to make the experiment longer (35 days) to see further changes during the storage.

Abstract bachelorproef 1 2016-2017: Impact of trans-cinnamaldehyde on the enzymatic browning of iceberg lettuce

The focus of this bachelor thesis was to determine the influence of natural compounds (trans-cinnamaldehyde and chlorogenic acid) on the enzymatic browning of minimal processed fresh-cut iceberg lettuce in order to prolong the shelf life. Besides appearance and loss of desirable texture, browning is one of the fundamental factors affecting the quality loss in minimally processed iceberg lettuce and leads to an economic disadvantage. The key enzymes in this enzymatic browning process are phenylalanine ammonia lyase (PAL), polyphenol oxidase (PPO) and peroxidase (POD). A treatment of iceberg lettuce with a natural component to increase the shelf life, is a healthy alternative and might reduce the use of chemical additives in the food industry.

Iceberg lettuce was bought in a local grocery store and processed in order to obtain a homogeneous batch of midrib tissue. Lettuce samples were treated with a solution of chlorogenic acid and trans-cinnamaldehyde. Using spectrophotometrical methods, several parameters (BP and activity of PAL, PPO & POD) were monitored during 14 days of refrigerated storage in plastic bags.

Trans-cinnamaldehyde treatment was studied more in detail by microbial analysis and differentiating treatment times. Results of these experiments can be used for further optimization of the trans-cinnamaldehyde treatment in order to inhibit enzymatic browning in iceberg lettuce.

Abstract bachelorproef 2 2016-2017: Impact of mineral enhancers on the bioaccessibility of iron and zinc in fermented cereal porridges

In developing countries (like Zimbabwe), there is a low bioaccessibility of trace minerals (iron and zinc) in fermented cereal porridges, which can lead to nutrient deficiency. This low bioaccessibility is caused by the presence of mineral inhibitors (phytic acid, phenolic compounds and condensed tannins), which are naturally present in cereals. By the addition of mineral enhancers (ascorbic acid, meat factor) or by adding enzymes (phytase, laccase, tannase), the bioaccessibility of iron and zinc could be increased.

Different mineral enhancers were added to the fermented porridges in a ratio 1:3. Different spectrophotometrically methods were used to determine the amount of the mineral inhibitors. An in vitro digestion was performed to have an estimation of the mineral bioaccessibility.

The fermented slurries with mineral enhancers still have an amount of mineral inhibitors, a decrease of the phytic acid and an increase of the phenolic compounds was observed. The amount of iron and zinc was increased in the fermented slurries when mopane worm powder was added, but only a small fraction was available for uptake in the body. Adding baobab to the fermented slurries had a positive influence on the bioavailability of iron and zinc. In the cereals treated with the enzymes, phytase was the only enzyme having a positive effect in the decrease of phytic acids.

This experiment has shown that baobab and mopane worm powder were not able to increase the bioavailability of minerals in these fermented porridges. In future studies, the influence of enzymes (specially phytase) is interested to study more in detail.