Research Projects in 2023-2024

Analysis of the impact of non-thermal pretreatment on the microwave vacuum dehydration property of banana slices using terahertz time-domain spectroscopy and near-infrared hyperspectral imaging (PhD)

Y Fu, Y Q Ren and Da-Wen Sun

Sponsors: CSC-UCD Scholarship Scheme

Bananas as fruit are rich in nutritional value, their perishable nature poses a great challenge to the transport and storage process. Dehydration techniques can ensure the quality of the product while retaining a high degree of nutrients. This study investigated the impact of four non-thermal pretreatment methods including osmotic dehydration, ultrasound osmotic dehydration and ascorbic acid on the dehydration nature of banana slices. 

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Novel analysis of food processes by terahertz spectral imaging: a review of recent research finding (PhD)

Y Fu, Y Q Ren and Da-Wen Sun

Sponsors: CSC-UCD Scholarship Scheme

Process analysis is an important step for online food quality control during food processing. Among the emerging non-destructive examination techniques that offer rapid detection, terahertz spectroscopy has attracted attention in analysing food processes based on various quality parameters. Moreover, calibration and chemometric methods are frequently used for spectral data analysis. The system normally consists of processing equipment and terahertz time-domain spectral imaging (THz-TDS), which often exhibits high prediction accuracy combined with appropriate chemometrics methods. Therefore, terahertz spectroscopy has been considered highly suitable for on-site and in-situ process analysis to enhance manufacturing and thus improve product quality. Applications of THz-TDS in food processes of dehydration, storage, freezing, and fermentation, as well as other areas, are introduced and discussed. Among these, terahertz technology has attracted intensive research for process analysis related to moisture changes, such as dehydration and storage under natural drying conditions.The combination of THz-TDS with calibration and chemometrics has been widely employed in analysing the non-linear changes of quality attributes during food processing with the emergence of numerous related research in recent years. It is highly suitable for analysing moisture content and other polar substances such as hydrogen sulfide and ammonia. Despite such high performance, drawbacks of high cost, interference from high moisture content, and high disturbance of other constituents such as protein are still significant obstacles to the universalization of THz-TDS.

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Utilizing lipid-rich microalgae for the valorization of dairy wastewater (PhD)

M S Xiao, Da-Wen Sun and R Halim

Sponsors: CSC-UCD Scholarship Scheme

The burgeoning global economy and population expansion have sparked a surge in demand for dairy products, resulting in a significant increase in the generation of nutrient-rich byproducts that pose substantial environmental challenges. To tackle this issue, microalgae-based wastewater treatment has emerged as a compelling alternative solution for nutrient recovery from dairy processing side streams. In this study, a novel cultivation strategy of microalgae in dairy wastewater was investigated, employing lipid-rich microalgae Nannochloropsis as a sustainable and potentially cost-effective solution for dairy wastewater management. Nannochloropsis demonstrated efficient removal of nutrients from dairy wastewater. Simultaneously, a substantial amount of biomass was generated with enhanced lipid accumulation. These findings underscore the species’ potential as a promising and sustainable solution for treating wastewater from the dairy industry, while offering opportunities for lipid production.

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Valorisation and Exploration of marine side streams under novel technologies processing (PhD)

W R Dong, Da-Wen Sun and B K Tiwari

Sponsors: CSC-UCD Scholarship Scheme

The project aims to advance the valorization of marine side streams through the deployment of novel technologies, focusing on maximizing the utility of both solid and liquid waste streams in the marine industry. Emphasizing a zero-waste ethos, the initiative is designed to extract valuable components from solid waste, such as fish protein and omega-rich oils, as well as chitin and chitosan from shellfish. These extractions contribute to a circular economy by transforming by-products into high-value inputs for various industries, ranging from agriculture to pharmaceuticals.

Liquid waste processing is another critical facet of the project, with the goal of repurposing nutrient-laden waters from fish processing facilities. Through innovative methods, these streams are utilized to cultivate duckweed and microalgae, enriching the production of bio-based products. This approach not only minimizes environmental impact but also capitalizes on the growth potential of aquaculture by-products.

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Predicting wheat gluten concentrations in potato starch using GPR and SVM models built by terahertz time-domain spectroscopy (PhD)

Q X Li, T Lei, Y L Cheng, X Wei and Da-Wen Sun

Sponsors: CSC-UCD Scholarship Scheme

This study explored for the first time the possibility of using terahertz (THz) spectral imaging to detect gluten content in food samples, offering a rapid, non-destructive alternative to traditional gluten detection methods. By examining mixed samples of potato starch with varying gluten concentrations, the research established Gaussian Process Regression (GPR) and Support Vector Machine (SVM) models for predicting gluten content. The GPR model, particularly using the Matern 5/2 algorithm, demonstrated superior prediction performance compared to the SVM model across a gluten concentration range of 1.3% to 100%. This finding suggests the potential of THz spectral imaging combined with GPR modeling as an effective tool for quickly and accurately identifying gluten-free foods.

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Comparing the predictive power of near-infrared and terahertz spectroscopy for chemical composition concentrations in biscuits (PhD)

Q X Li and Da-Wen Sun

Sponsors: CSC-UCD Scholarship Scheme

This study aims to compare the strengths and specific sensitivities of different spectroscopic technologies in food analysis. Near-infrared (NIR) spectroscopy enables quantification of moisture, fat, and protein levels, crucial parameters in biscuit quality control. Terahertz (THz) spectroscopy, sensitive to a different segment of the chemical spectrum, detects low-frequency molecular vibrations, which can be pivotal in identifying complex carbohydrates and other ingredients in biscuits. By comparatively evaluating the predictive power of NIR and THz spectroscopy, this research shows the complementary nature of these technologies. Each has its specific spectral sensitivity that, if combined, provides a comprehensive picture of chemical composition in biscuits. The study shows the broader trend in the food industry towards using different analytical strengths of various spectroscopic methods to improve product quality and manufacturing sustainability.

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A model combining near-infrared and terahertz spectroscopy to enhance the prediction accuracy of components in sunflower seeds (PhD)

Q X Li and Da-Wen Sun

Sponsors: CSC-UCD Scholarship Scheme

This study aimed to investigate the accuracy and reliability of near-infrared (NIR) spectroscopy combined with terahertz (THz) spectroscopy for quantitative analysis of the chemical composition of food samples. Traditionally, NIR and THz spectroscopy have been used separately in food analysis. While NIR spectroscopy has advantages in terms of nondestructive and speed, THz spectroscopy is prized for its ability to penetrate deep into the sample, making it suitable for detecting internal quality. A detailed comparison of NIR and THz spectral data from commercially available sunflower seed samples was conducted to evaluate the effectiveness of the combined use of the two techniques in improving the accuracy of ingredient detection and to explore how to effectively integrate the two spectral data to maximize their benefits in food analysis. This study demonstrates a new food detection strategy and provides the food industry with an effective method to ensure the quality and safety of food for the public. It also provides new perspectives and tools for analyzing other materials and compounds.

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Novel post-harvest techniques and their impacts on the undesirable factors alternative protein source (PhD)

G Y Dong, Da-Wen Sun and B K Tiwari

Sponsors: CSC-UCD Scholarship Scheme

The current growing demand for sustainable plant proteins, as well as concerns about allergens and antinutrients, require novel technologies to optimize processing and minimize allergens and antinutrients in isolated plant proteins. Seaweed is a promising but underexplored alternative protein source. According to European food safety authorities, novel food products should be labeled for allergenicity due to food safety concerns. Therefore, reducing the allergenicity of seaweed should become an important task in developing new safe foods. This study aimed to investigate the effect of ultrasound therapy alone or in combination with microwaves on Alaria esculenta sensitization. Seven pretreatments were performed on Alaria Esculenta, including traditional hot water blanching (HWB), novel ultrasonic blanching, and microwave blanching. Three allergens from two major types of allergen proteins, namely tropomyosin (Hel as 1 from molluscs and Pen i 1 from crustaceans) and parvalbumin (from fishes). In terms of anti-nutrients, high pressure processing (HPP), hydrodynamic cavitation (HDC), ultrasonic treatment (US), microwave treatment (MP) and agitation were evaluated for improving protein content and modulating anti-nutrients such as phytic acid, trypsin inhibitor activity (TIA) and tannins.The products involved include protein isolates from two species of macroalgae (Alaria esculenta and Chondrus Cripus) and two legumes (pea and fababean). 

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Protein extraction from potatoes, sweet potatoes and their by-products using novel technology (PhD)

Z P Hu, G Y Dong, J Naibaho, Da-Wen Sun and B K Tiwari

Sponsors: CSC-UCD Scholarship Scheme

Tuber foods are characterized by high yield and high waste. Tuber proteins have extremely high nutritional value and interesting properties as a potential protein source. Several novel extraction techniques are utilized to recover proteins from potatoes, sweet potatoes and their by-products. The applied technologies include ultrasonic assisted extraction, microwave assisted extraction, enzyme assisted extraction, hydraulic cavitation assisted extraction and pulsed electric field assisted extraction. The resulting products will be subjected to nitrogen content, high performance liquid chromatography, Fourier transform infrared spectroscopy and amino acid analysis to evaluate the effectiveness of various techniques. The research aims to make the process more sustainable and efficient through novel technologies that can maximize the use of all components of the tuber plant, reduce waste and create new revenue streams.

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Effect of mono-frequency ultrasound and dual-frequency ultrasound at different pH on structure and physicochemical properties of faba bean proteins (PhD)

S Y Wang, Da-Wen Sun and M Song

Sponsors: CSC-UCD Scholarship Scheme

Faba bean proteins isolate (FPI) are candidates for animal protein alternatives. However, the application of them meets many challenges due their physicochemical and functional properties. It is necessary to use modification approaches to improve these properties and change the limitation. Ultrasound treatment is an efficient modification method which can change the protein structure and properties. The objective of the study was to evaluate how ultrasound treatment with different frequency at different pH modified the structure and physicochemical properties of faba bean proteins. In the study, faba bean protein isolates (FPIs) were treated by ultrasound with different frequency (20 kHz, 40 kHz and 20+40 kHz) and adjusted to different pH (3, 7, and 9). Then the structure and physicochemical properties of control and untreated FPIs were investigated. The ultrasound treatment had no obvious effect on the molecular weight of FPI, whereas it changed the secondary structure of FPI from a more ordered structure to a more disordered structure. The structure change can further lead to the difference in physiochemical properties of FPI, including surface hydrophobicity, zeta potential, particle size, solubility and thermal properties. Ultrasound treatment at 20 kHz and 20+40 kHz had more influence in the properties compared to that at 40 kHz.

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Effects of heat treatment and pH-shifting on physical stability of faba bean protein-stabilized pickering emulsions (PhD)

S Y Wang, Da-Wen Sun and M Song

Sponsors: CSC-UCD Scholarship Scheme

The emulsion commonly exists in food products. Various emulsifiers are added into food to keep stability of emulsion. Proteins can serve as natural emulsifiers due to the amphiphilic properties. Faba bean protein is a potential plant protein. The native faba bean has been studied as a natural emulsifier in oil-in-water (O/W) emulsions. To further improve stability of the emulsions, some modification of faba bean protein should be studied. Heat treatment is the most common method used to modify the physicochemical and functional properties of protein. And it be an efficient way for reduction of adverse effects of anti-nutritional compounds in plant proteins. pH shifting is a chemical treatment in which protein samples are exposed to an extreme alkaline or acidic pH to unfold the proteins, followed by readjustment of the pH to neutrality. It has been reported other plant protein treated by this method can improve emulsion stability. The aim of the study was to evaluate the effect of heat treatment and pH shifting on the stability of faba bean protein-stabilized pickering emulsions. Heat treatment and pH shifting modified the properties of faba bean proteins, including solubility, zeta potential and surface hydrophobicity. The change of properties improved the stability of faba bean protein-stabilized pickering emulsions. pH shifting resulted in more improvements in the emulation stability than heat treatment.

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In-situ indirect measurements of real-time moisture contents during microwave vacuum drying of beef and carrot slices using terahertz time-domain spectroscopy (PhD)

Y Q Ren, T Lei and Da-Wen Sun

Sponsors: CSC-UCD Scholarship Scheme

Moisture content (MC) is a critical quality indicator for food drying processing, however achieving in-situ non-destructive analyses of dynamic MC of products during processing is still a challenge. This study developed an in-situ indirect measurement method using Terahertz time-domain spectroscopy (THz-TDS) for real-time MC prediction of foods during microwave vacuum drying (MVD). During MVD, THz-TDS continuously sense the dynamic moisture vapour from the desiccator through a polyethene air hose. The obtained THz spectra were processed to calibrate MC loss prediction models using support vector regression, Gaussian process regression and ensemble regression. Then the MC was calculated using moisture loss prediction results. The best real-time MC prediction results for beef and carrot slices achieved R2 of 0.995, RMSE of 0.0162, and RDP of 22. The developed system provides a novel method for drying kinetics research during MVD and expands the applicability of the THz-TDS technique in the food industry.

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Analyzing the effects of nonthermal pretreatments on the quality of microwave vacuum dehydrated beef using terahertz time-domain spectroscopy and near-infrared hyperspectral imaging (PhD)

Y Q Ren, Y Fu and Da-Wen Sun

Sponsors: CSC-UCD Scholarship Scheme

Both nonthermal pretreatment and nondestructive analysis are effective technologies in improving drying processes. This study evaluated the effects of different pretreatment methods on the quality of beef dehydrated by microwave vacuum drying (MVD) and compared the MVD process performance comprising real-time moisture content (MC), MC loss, colour content, and shrinkage rate using different optical sensing methods including terahertz time-domain spectroscopy (THz-TDS) and near-infrared hyperspectral imaging (NIR-HSI). Results indicated that osmotic pretreatment improved the drying rate of MVD beef with lower changes in colour and shrinkage rate. Both THz-TDS-based and NIR-HSI-based on-site direct scanning and in-situ in-direct sensing showed accurate prediction results, with best R2p of 0.9646 and 0.9463 for MC and R2p of 0.9817 and 0.9563 for MC loss prediction, respectively. NIR-HSI visualisation of MC results showed that ultrasound pretreatment curbed but osmotic pretreatment promoted nonuniform distribution during MVD. This research should guide improving the industrial MVD drying process.

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Comparative studies on enhancing pea protein extraction recovery rates and structural integrity using ultrasonic and hydrodynamic cavitation technologies (PhD)

J F Tang, Da-Wen Sun and B K Tiwari

Sponsors: CSC-UCD Scholarship Scheme

The study explored the efficacy of various cavitation technologies, including ultrasonic bath (USB), ultrasonic plate (US-plate), ultrasonic probe (US-probe), and hydrodynamic cavitation (HDC), in extracting proteins from peas. US-probe showed highest protein recovery rate (52.53 g/hg protein in pea powder) among all lab-scale cavitation equipment while HDC demonstrated significant potential for scaling up, notably improving both the purity (80.35 g/hg dried precipitate) and recovery rate (56.85 g/hg) of pea protein isolate (PPI) compared to conventional extraction (CE). SDS-PAGE, LC-MS/MS, FTIR and Fluorescence analysis were used to analyse the impact of these cavitation technologies on the structures of pea protein. The results confirmed that cavitation preserved PPI’s primary structure while altering its secondary and tertiary structures, particularly under US-probe treatment, which significantly unfolded proteins. The SEM results revealed a marked reduction in protein bodies adhering to starch granules in residues from US-probe and HDC treatments compared to CE, correlating with their higher protein recovery rates.

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Synergistic effects of combined microwave and ultrasound-assisted extraction on yield and functional properties of lupin protein (PhD)

J F Tang, Da-Wen Sun and B K Tiwari

Sponsors: CSC-UCD Scholarship Scheme

The study evaluated the synergy between microwave (MW) and ultrasonic (US) technologies in facilitating lupin protein extraction. Compared to conventional method with its protein recovery rate of 44.72%, the combination application of MW and US notably increased extraction efficiency, with an optimal protein recovery rate of 56.69% achieved under conditions of 100% amplitude US coupled with 50% amplitude MW. Furthermore, the combination of US and MW not only elevated protein solubility and viscosity but also induced a reduction in particle size of protein isolate. Structural modifications induced by this hybrid technique were evidenced through SDS-PAGE and FTIR spectroscopy, suggesting significant alterations in protein conformation. These findings underscore the potential of MW and US co-treatment in optimizing lupin protein extraction and modifying its functional attributes, contributing to its broader applicability in food and nutraceutical formulations.

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Antimicrobial effects of plasma-activated water from cold and thermal plasma systems on biofilms formed on different surfaces (PhD)

Y L Zhao, B K Tiwari and Da-Wen Sun

Sponsors: CSC-UCD Scholarship Scheme

Plasma-activated water (PAW) is generated by both thermal and cold atmospheric plasma for 15- and 30-min. Physicochemical properties of PAW, including pH, oxidation-reduction potential (ORP), and levels of reactive oxygen and nitrogen species (RONS) including H₂O₂, NO₂^– and NO₃^– are measured. Stainless steel and glass are used as surfaces for Saccharomyces cerevisiae DSM 70449 biofilm formation. After 48 h of formation, PAW is added immediately after generation and the viable counts at different exposure times of 15 and 30 min are examined to determine the inactivation efficacy. The viable counts in the biofilms on different surfaces before and after treatment are determined via the plate counting method. The production of intracellular RONS in the biofilms after being exposed to PAW is measured using 2’,7’- dichlorofluorescin diacetate (DCFH-DA) assay (for intracellular ROS detection) and 4-amino-5-methylamino-2′,7′-dichlorofluorescin diacetate (DAF-FM DA) assay (for intracellular RNS detection). Scanning electron microscopy (SEM) images of the biofilms are conducted to examine the morphological changes after PAW exposure. This study demonstrates the disruption and inactivation of biofilms formed on different surfaces by PAW generated by both atmospheric air technologies. The changes in PAW physiochemical properties (levels of RONS) could correspond to the intracellular RONS detected in cells. The reduction in biofilm cell counts could be related to the change of intracellular RONS observed in the treated cells. The SEM results indicate atmospheric air technologies affected the biofilm cell morphology and cell viability. 

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Research on analysis and detection using novel terahertz spectroscopy technique in polysaccharides-related research: principle, structure and application advances (PhD)

T J Chen and Da-Wen Sun

Sponsors: CSC-UCD Scholarship Scheme

Terahertz (THz) spectroscopy, as a novel detection technology has performed outstanding prospective in polysaccharides analysis.in this review, the basic principle of THz spectroscopy techniques is presented. Advanced THz spectroscopy used in quantitative and qualitative analysis, conformation, structure analysis and detection in polysaccharides are studied in this review from 2002 to 2024, which discuss identification and analyses of polysaccharide content types, molecular weight ranges and their functional groups, conformation analysis of polysaccharides, polysaccharides interaction analysis. Besides, other spectroscopic techniques applied on analysis of polysaccharides are compared with THz spectroscopy techniques and challenges and perspectives of THz spectroscopy in polysaccharides are also pointed out.

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