Advanced Optical Technologies in Food Quality and Waste Management

Food waste is a global problem caused in large part by premature food spoilage. Seafood is especially prone to food waste because it spoils easily. Of the annual 4.7 billion pounds of seafood destined for U.S. markets between 2009 and 2013, 40 to 47 percent ended up as waste. This problem is due in large part to a lack of available technologies to enable rapid, accurate, and reliable valorization of food products from boat or farm to table. Fortunately, recent advancements in spectral sensing technologies and spectroscopic analyses show promise for addressing this problem. Not only could these advancements help to solve hunger issues in impoverished regions of the globe, but they could also benefit the average consumer by enabling intelligent pricing of food products based on projected shelf life. Additional technologies that enforce trust and compliance (e.g., blockchain) could further serve to prevent food fraud by maintaining records of spoilage conditions and other quality validation at all points along the food supply chain and provide improved transparency as regards contract performance and attribution of liability. In this chapter we discuss technologies that have enabled the development of hand-held spectroscopic devices for detecting food spoilage. We also discuss some of the analytical methods used to classify and quantify spoilage based on spectral measurements

Manufacture and utilization of a biodegradable sensor platform from gold coated zein nanophotonic films to detect acrylamide and Ara-h1 using SERS

With the current developments in biosensor and nanotechnology, detection of analyses that are important to food industry are becoming more commonplace. One of the strong tools that nanotechnology enabled is Surface Enhanced Raman Spectroscopy (SERS). SERS is a highly sensitive and specific technique which provides molecular fingerprinting, with the enhancement effect as a result of roughened noble metal surfaces. The platform for these surfaces are generally made out of non-biodegradable, plastic materials. As the one-time use, large scale applications are needed for many fields such as medical, forensic and food industry, disposability of these sensors will pose a problem in the future. In the scope of this dissertation, we investigated the feasibility of a biodegradable sensor platform that is made of zein, a corn protein, utilized in SERS measurements of food analytes. First, the effect of parent substrate (the surface, which zein was cast on) and plasticizer, oleic acid content, on the surface hydrophilicity of resulting zein films was analyzed. It was found that the surface chemistry of the parent substrate was more important than the topography of the parent substrate. Oxygen plasma was used to make the polydimethylsilohexane (PDMS) surfaces more hydrophilic and it was found that zein film surfaces that were in contact with PDMS also had more hydrophilic surfaces, compared to regular PDMS, which is a hydrophobic material. Water contact angle (WCA) method was used to quantify the hydrophilicity of zein films. WCA reached values as low as 20 degrees with a high oleic acid content. Increase in oleic acid content in the formulation of zein films as well as the parent substrate chemistry was found to influence the water affnity of zein films. In the development of the fabrication method of nanopatterned and gold coated zein surfaces, a simultaneous three-dimensional transfer was used. Four different nanopatterns, namely positive pyramids, inverted pyramids, nano pillars and nano pores were transferred onto zein films along with either 80 or 200 nm gold coating by using solvent casting technique. Scanning microscopy images showed that the patterns were transferred onto zein films with high fidelity and success. The enhancement effect of these SERS substrates were tested by using a model molecule, Rhodamine 6G. It was found that the best enhancement effect was provided by inverse-pyramid structures coated with 200 nm gold. For the rest of the study, these structures were used. Zein-SERS substrates were utilized in two different food analyte detection purpose, acrylamide and peanut allergen protein Ara h1. Acrylamide is a potential carcinogenic compound that is formed during high temperature food processing. French fries, potato chips, bread and coffee are some of the food products that may contain high amounts of acrylamide. Since Food and Drug Administration released a draft advisory for mitigation strategies for acrylamide content in foods, there is a need for routine testing technique of acrylamide in food products. In this research, acrylamide was detected by using zein-SERS substrates as a proof of concept. Limit of detection was found to be 10 micrograms/milliliter. Calibration curve was obtained with an R2 value of 0.93 and 0.97 for log-log version. Peanut allergies are among the most common food allergies, and they can result in life-threatening reactions in allergic patients. For this reason, it is extremely important to monitor the presence or cross-contamination of peanuts into food products. There are 8 identified peanut allergen proteins and Ara h1, consists of the largest percentage of protein content, in addition to causing reactions in almost 100 % of the patients. Zein-SERS substrates were utilized in detection of Ara h1. With the use of statistical clustering technique called principal component analysis (PCA), it was possible detect and quantify Ara h1 protein. Limit of detection was found to be 0.14 mg/ml. The surface of the zein-SERS substrates were functionalized with monoclonal antibody and tested for capturing Ara h1 as a proof-of-concept. With this research, utilizing zein as a biodegradable sensor platform for SERS measurements were investigated for the first time. It was shown that detection of both acrylamide and Ara h1, peanut protein, was possible. The methods developed in this study for controlling the surface hydrophilicity of zein films and direct transfer of both micro and nano-scale patterns onto zein along with noble metals can be employed in other biosensor and biopolymer applications as well in the future. This kind of biodegradable platforms might be an alternative solution for environmentally friendly and large scale sensor applications

Effect of drying on the kinetics, stability of active ingredients and non- destructive testing of Backhousia citriodora (lemon myrtle) dehydrated leaves

The dehydration process of lemon myrtle leaves (LML) in Malaysia is still conducted by using conventional method of drying that takes long duration thus decreasing the quality of the dried LML. To prolong the shelf life, LML has to be dried to reduce its moisture content. The present research highlighted the drying kinetics, application of heat pump drying on LML and the application of non- destructive testing on moisture content analysis of dried LML. In the present study, LML were dried by OD (40 to 60°C), VD (40 to 60°C at 50 mbar) and HPD (45°C). Both engineering properties (drying kinetics, effective moisture diffusivity and activation energy) and quality properties (colour, biochemical content and volatile content) of all dried LML were assessed and evaluated. All drying methods only exhibited falling rate period, indicating that the drying was governed by the movement of internal moisture to the surface for evaporation. The moisture diffusivity (Deff) was found to vary in range of 8.07 x 10-10 to 4.53 x 10-9 m2/s for all drying methods and conditions. The activation energy (Ea) was obtained and the values were 13.42 kJ/mol, 45.41 kJ/mol and 72.85 kJ/mol for HPD, VD and OD, respectively. It was found that the drying air velocity of 2.0 m/s (FR2.0) in the HPD was the suitable drying condition as it gave minimum colour changes and the highest retention of volatiles which was recorded at 89.5%. The total phenolic content (TPC) and antioxidant activities of samples drying at 2.0 m/s also showed high retention, recorded at 74%, 95% and 80% for TPC, 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and ferric reducing antioxidant potential (FRAP), respectively. It was found that HPD sample gave the highest value of greenness (a*) with the lowest value of total colour difference and browning index. For biochemical content, VD samples showed high retention of TPC, DPPH and FRAP assay followed by HPD samples, while OD samples showed the lowest biochemical content for all drying conditions. The essential oil of the dehydrated LML subjected to OD50, VD50 and HPD was extracted by using simultaneous distillation and extraction (SDE) method and analysed for its volatile compounds by using Gas Chromatography-Mass Spectrometer (GC- MS). HPD samples showed the highest retention of volatiles compounds especially cis- and trans-citral with a total concentration of 89.5%. Dehydrated LML were packed under four different conditions, normal and vacuum packaging (N and V), each of the packaging was placed at room temperature (25°C) or chilled condition (4°C) (RT and CH) stored for a period of 6 months. It was found that the vacuum packaging yielded higher retention of colour and biochemical content than the non-vacuum packaged LML. This approach combined with storage at lower temperature (4°C) resulted in a better retention of green colour and higher percentages of TPC, DPPH and FRAP (49%, 72% and 56% respectively) for HPD samples. Partial least squares regression (PLSR) and cross-validation modelling were used to explore the feasibility of these spectroscopic techniques over three types of prediction models which were full spectral ranges of near infrared (NIR) and dielectric measurement (DM), selected spectral range of NIR and fusion of both non- destructive methods. NIR model gave the highest coefficient of determination, r value of more than 0.99 and ratio performance to deviation (RPD) value of 3.16 that indicated excellent prediction of moisture content in the dried LML. The selected spectra analysis of NIR spectra showed no improvement in PLSR results. Whereas, fusion of the non-destructive models showed improvement of the r, root mean square error and RPD values especially for DM method. The effect of drying on the stability of active ingredients of Backhousia citridora (lemon myrtle) dehydrated leaves was investigated and discussed in this study. HPD was found to be a suitable method for LML dehydration, as it resulted in the highest retention of volatiles compound, greenness and antioxidant values after drying and after 6 months storage. The high quality of dehydrated LML subjected to HPD ensures the market acceptability as well as its functionality. Therefore, this study suggested that HPD with drying air velocity of 2.0 m/s could be used as a proper dehydration process for LML that preserve its functionality for the applications of nutraceuticals, cosmeceuticals and pharmaceuticals

Effect of drying on the kinetics, stability of active ingredients and non- destructive testing of Backhousia citriodora (lemon myrtle) dehydrated leaves

The dehydration process of lemon myrtle leaves (LML) in Malaysia is still conducted by using conventional method of drying that takes long duration thus decreasing the quality of the dried LML. To prolong the shelf life, LML has to be dried to reduce its moisture content. The present research highlighted the drying kinetics, application of heat pump drying on LML and the application of non- destructive testing on moisture content analysis of dried LML. In the present study, LML were dried by OD (40 to 60°C), VD (40 to 60°C at 50 mbar) and HPD (45°C). Both engineering properties (drying kinetics, effective moisture diffusivity and activation energy) and quality properties (colour, biochemical content and volatile content) of all dried LML were assessed and evaluated. All drying methods only exhibited falling rate period, indicating that the drying was governed by the movement of internal moisture to the surface for evaporation. The moisture diffusivity (Deff) was found to vary in range of 8.07 x 10-10 to 4.53 x 10-9 m2/s for all drying methods and conditions. The activation energy (Ea) was obtained and the values were 13.42 kJ/mol, 45.41 kJ/mol and 72.85 kJ/mol for HPD, VD and OD, respectively. It was found that the drying air velocity of 2.0 m/s (FR2.0) in the HPD was the suitable drying condition as it gave minimum colour changes and the highest retention of volatiles which was recorded at 89.5%. The total phenolic content (TPC) and antioxidant activities of samples drying at 2.0 m/s also showed high retention, recorded at 74%, 95% and 80% for TPC, 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and ferric reducing antioxidant potential (FRAP), respectively. It was found that HPD sample gave the highest value of greenness (a*) with the lowest value of total colour difference and browning index. For biochemical content, VD samples showed high retention of TPC, DPPH and FRAP assay followed by HPD samples, while OD samples showed the lowest biochemical content for all drying conditions. The essential oil of the dehydrated LML subjected to OD50, VD50 and HPD was extracted by using simultaneous distillation and extraction (SDE) method and analysed for its volatile compounds by using Gas Chromatography-Mass Spectrometer (GC- MS). HPD samples showed the highest retention of volatiles compounds especially cis- and trans-citral with a total concentration of 89.5%. Dehydrated LML were packed under four different conditions, normal and vacuum packaging (N and V), each of the packaging was placed at room temperature (25°C) or chilled condition (4°C) (RT and CH) stored for a period of 6 months. It was found that the vacuum packaging yielded higher retention of colour and biochemical content than the non-vacuum packaged LML. This approach combined with storage at lower temperature (4°C) resulted in a better retention of green colour and higher percentages of TPC, DPPH and FRAP (49%, 72% and 56% respectively) for HPD samples. Partial least squares regression (PLSR) and cross-validation modelling were used to explore the feasibility of these spectroscopic techniques over three types of prediction models which were full spectral ranges of near infrared (NIR) and dielectric measurement (DM), selected spectral range of NIR and fusion of both non- destructive methods. NIR model gave the highest coefficient of determination, r value of more than 0.99 and ratio performance to deviation (RPD) value of 3.16 that indicated excellent prediction of moisture content in the dried LML. The selected spectra analysis of NIR spectra showed no improvement in PLSR results. Whereas, fusion of the non-destructive models showed improvement of the r, root mean square error and RPD values especially for DM method. The effect of drying on the stability of active ingredients of Backhousia citridora (lemon myrtle) dehydrated leaves was investigated and discussed in this study. HPD was found to be a suitable method for LML dehydration, as it resulted in the highest retention of volatiles compound, greenness and antioxidant values after drying and after 6 months storage. The high quality of dehydrated LML subjected to HPD ensures the market acceptability as well as its functionality. Therefore, this study suggested that HPD with drying air velocity of 2.0 m/s could be used as a proper dehydration process for LML that preserve its functionality for the applications of nutraceuticals, cosmeceuticals and pharmaceuticals

Investigation of Volatile Organic Compounds (VOCs) released as a result of spoilage in whole broccoli, carrots, onions and potatoes with HS-SPME and GC-MS

Vegetable spoilage renders a product undesirable due to changes in sensory characteristics. The aim of this study was to investigate the change in the fingerprint of VOC composition that occur as a result of spoilage in broccoli, carrots, onions and potatoes. SPME and GC-MS techniques were used to identify and determine the relative abundance of VOC associated with both fresh and spoilt vegetables. Although a number of similar compounds were detected in varying quantities in the headspace of fresh and spoilt samples, certain compounds which were detected in the headspace of spoilt vegetables were however absent in fresh samples. Analysis of the headspace of fresh vegetables indicated the presence of a variety of alkanes, alkenes and terpenes. Among VOCs identified in the spoilt samples were dimethyl disulphide and dimethyl sulphide in broccoli; Ethyl propanoate and Butyl acetate in carrots; 1-Propanethioland 2-Hexyl-5-methyl-3(2H)-furanone in onions; and 2, 3-Butanediol in potatoes. The overall results of this study indicate the presence of VOCs that can serve as potential biomarkers for early detection of quality deterioration and in turn enhance operational and quality control decisions in the vegetable industry