Theodore P. Labuza

Water Activity in Foods: Fundamentals and Applications

1. Introduction - Historical Highlights of Water Activity Research. Jorge Chirife and Anthony J. Fontana, Jr. 2. Water Activity - Fundamentals and Relationships. David S. Reid. 3. Water Activity and Glass Transition. Yrjo H. Roos. 4. Water Mobility in Foods. Shelly J. Schmidt. 5. Water Activity Prediction and Moisture Sorption Isotherms. T.P. Labuza and B. Altunakar. 6. Measurement of Water Activity, Moisture Sorption Isotherms, and Moisture Content of Foods. Anthony J. Fontana, Jr. 7. Moisture Effects on Food Chemical Stability. Leonard N. Bell. 8. Water Activity and Physical Stability. Gaelle Roudaut. 9. Diffusion and Sorption Kinetics of Water in Foods. T.P. Labuza and B. Altunakar. 10. Effects of Water Activity on Microbial Stability - as a Hurdle in Food Preservation. Maria S. Tapia, Stella M. Alzamora, and Jorge Chirife. 11. Principles of Intermediate-Moisture Foods and Related Technology. Petros S. Taoukis and Michelle Richardson. 12. Desorption Phenomena in Food Dehydration Processes. G.V. Barbosa-Canovas and P. Juliano. 13. Applications of Water Activity Management in the Food Industry. Jorge Welti-Chanes, Emmy Perez, Jose Angel Guerrero-Beltran, Stella M. Alzamora, and Fidel Vergara-Balderas. 14. Applications of Water Activity in Non-Food Systems. Anthony J. Fontana, Jr. and Gaylon S. Campbell. 15. The Future of Water Activity in Food Processing and Preservation. Cynthia M. Stewart, Ken A. Buckle, and Martin B. Cole. Appendix A: Water Activity of Saturated Salt Solutions. Appendix B: Water Activity of Unsaturated Salt Solutions at 25-C. Appendix C: Water Activity and Isotherm Equations. Appendix D: Minimum Water Activity Limits for Growth of Microorganisms. Appendix E: Water Activity Values of Selected Food Ingredients and Products. Appendix F: Water Activity Values of Select Consumer and Pharmaceutical Products. Index

Detection of a foreign protein in milk using surface-enhanced raman spectroscopy coupled with antibody-modified silver dendrites

Herein we developed a rapid and simple method which used surface-enhanced Raman spectroscopy (SERS) coupled with antibody-modified silver dendrites to detect ovalbumin (OVA), the egg white protein, introduced into whole milk. OVA was first captured out of milk by use of antibody-modified silver dendrites and then directly measured on the silver dendrites by Raman spectroscopy. Results show that this method is capable of detecting OVA at 0.1 μg/mL in phosphate buffered saline (PBS) and 5 μg/mL in milk within 30 min based on the principal component analysis. This method has the potential for wide use in areas such as allergenic protein detection and bioterrorism agent detection in complex matrixes.

Development of a single aptamer-based surface enhanced Raman scattering method for rapid detection of multiple pesticides

The objective of this study was to develop a simple and rapid method that could detect and discriminate four specific pesticides (isocarbophos, omethoate, phorate, and profenofos) using a single aptamer-based capture procedure followed by Surface Enhanced Raman Spectroscopy (SERS). The aptamer is a single stranded DNA sequence that is specific to capture these four pesticides. The thiolated aptamer was conjugated onto silver (Ag) dendrites, a nanostructure that can enhance the Raman fingerprint of pesticides, through Ag-thiol bonds. It was then backfilled with 6-mercaptohexanol (MH) to prevent nonspecific binding. The modified SERS platform [Ag-(Ap + MH)] was then mixed with each pesticide solution (P) for 20 min. After capturing the pesticides, the Ag-(Ap + MH)-P complex was analyzed under a DXR Raman microscope and TQ Analyst software. The results show that the four pesticides can be captured and detected using principal component analysis based on their distinct fingerprint Raman peaks. The limits of detection (LODs) of isocarbophos, omethoate, phorate, and profenofos were 3.4 μM (1 ppm), 24 μM (5 ppm), 0.4 μM (0.1 ppm), and 14 μM (5 ppm) respectively. This method was also validated successfully in apple juice. These results demonstrated the super capacity of aptamer-based SERS in rapid detection and discrimination of multi-pesticides. This technique can be extended to detect a wide range of pesticides using specific aptamers.

Aptamer-based surface-enhanced Raman scattering detection of ricin in liquid foods

A “two-step” aptamer-based surface-enhanced Raman scattering (SERS) detection assay was developed for ricin in liquid foods. Ricin B chain was first captured out of food matrices by aptamer-conjugated silver dendrites and then the spectrum was directly read on the silver dendrites. Aptamer use in this assay promotes ease of manipulation as well as improved sensitivity compared to antibody-based approaches. The limit of detection for ricin B chain was 10 ng mL−1 in phosphate buffered saline (PBS), 50 ng mL−1 in orange juice, and 100 ng mL−1 in milk based on principal component analysis (PCA) of measured spectra. This assay shows great promise as a rapid (< 40 min), sensitive, and simple “Yes/No” method to detect bio-weapons like ricin in liquid foods.

Effect of moisture content on selected physicochemical properties of two commercial hen egg white powders

After short-term storage at 23°C, selected physicochemical properties of two hen egg white powders (with and without hydrolysis) were studied. Overall, the effect of moisture content on physicochemical properties of Hydrolysed Egg White powder (HEW) was more severe than those of Dried Egg White powder (DEW). The denaturation temperature (Td) and its enthalpy change (ΔHd) of ovalbumin in DEW followed an exponential model, as well as the Td of HEW. The Gordon-Taylor equation modelled well the glass transition temperatures (Tg) of HEW and DEW. The Guggenheim-Anderson-de Boer (GAB) model fitted well to the type II moisture sorption isotherm. At the critical moisture content (12.0%, dry basis), compared with DEW, the colour of HEW began to darken dramatically and its hardness started to change significantly. These changes were closely related to the inherent characteristics of the two products. The mechanisms relevant to these physicochemical changes were discussed.

Recovery and quantitative detection of thiabendazole on apples using a surface swab capture method followed by surface-enhanced Raman spectroscopy

We developed a rapid and simple method which combines a surface swab capture method and surface-enhanced Raman spectroscopy for recovery and quantitative detection of thiabendazole on apple surfaces. The whole apple surface was swabbed and the swab was vortexed in methanol releasing the pesticide. Silver dendrites were then added to bind the pesticide and used for enhancing the Raman signals. The recovery of the surface swab method was calculated to be 59.4-76.6% for intentionally contaminated apples at different levels (0.1, 0.3, 3, and 5 ppm, μg/g per weight). After considering the releasing factor (66.6%) from the swab, the final accuracy of the swab-SERS method was calculated to be between 89.2% and 115.4%. This swab-SERS method is simple, sensitive, rapid (∼10 min), and quantitative enough for QA/QC in plant procedure. This can be extended to detect other pesticides on raw agricultural produce like pears, carrots, and melons etc.

A single DNA aptamer functions as a biosensor for ricin

The use of microorganisms or toxins as weapons of death and fear is not a novel concept; however, the modes by which these agents of bioterrorism are deployed are increasingly clever and insidious. One mechanism by which biothreats are readily disseminated is through a nations food supply. Ricin, a toxin derived from the castor bean plant, displays a strong thermostability and remains active at acidic and alkaline pHs. Therefore, the CDC has assigned ricin as a category B reagent since it may be easily amendable as a deliberate food biocontaminate. Current tools for ricin detection utilize enzymatic activity, immunointeractions and presence of castor bean DNA. Many of these tools are confounded by complex food matrices, display a limited dynamic range of detection and/or lack specificity. Aptamers, short RNA and single stranded DNA sequences, have increased affinity to their selected receptors, experience little cross-reactivity to other homologous compounds and are currently being sought after as biosensors for bacterial contaminants in food. This paper describes the selection and characterization of a single, dominant aptamer, designated as SSRA1, against the B-chain of ricin. SSRA1 displays one folding conformation that is stable across 4-63 °C (ΔG = -5.05). SSRA1 is able to concentrate at least 30 ng mL(-1) of ricin B chain from several liquid food matrices and outcompetes a currently available ELISA kit and ricin aptamer. Furthermore, we show detection of 25 ng mL(-1) of intact ricin A-B complex using SSRA1 combined with surface enhanced Raman scattering technique. Thus, SSRA1 would serve well as pre-analytical tool for processing of ricin from liquid foods to aid current diagnostics as well as a sensor for direct ricin detection.

Rapid Detection of Acetamiprid in Foods using Surface‐Enhanced Raman Spectroscopy (SERS)

Acetamiprid is a neonicotinoid pesticide that is commonly used in modern farming. Acetamiprid residue in food commodities can be a potential harm to human and has been implicated in the honey bee hive die off crisis. In this study, we developed rapid, simple, and sensitive methods to detect acetamiprid in apple juice and on apple surfaces using surface-enhanced Raman spectroscopy (SERS). No pretreatment of apple juice sample was performed. A simple surface swab method was used to recover acetamiprid from the apple surface. Samples were incubated with silver dendrites for several minutes and SERS spectra were taken directly from the silver surface. Detection of a set of 5 apple juice samples can be done within 10 min. The swab-SERS method took 15 min for a set of 5 samples. Resulting spectral data were analyzed using principal component analysis. The highest acetamiprid peak at 634 cm(-1) was used to detect and quantify the amount of acetamiprid spiked in 1:1 water-methanol solvent, apple juice, and on apple surface. The SERS method was able to successfully detect acetamiprid at 0.5 μg/mL (0.5 ppm) in solvent, 3 μg/mL (3 ppm) in apple juice, and 0.125 μg/cm(2) on apple surfaces. The SERS methods provide simple, rapid, and sensitive ways to detect acetamiprid in beverages and on the surfaces of thick skinned fruits and vegetables.

Applications and Perceptions of Date Labeling of Food

Open dating of food products has been practiced for decades, and has been key to achieving stock rotation at retail and providing information to consumers. The open date provides a simple communication tool, which may be based on product quality and/or food safety as determined by the manufacturer or retailer. Date marking is generally open but it can be closed (code intended for managing product at retail, and for recall and traceability), and the terminology and applications vary widely around the world. The variation in date labeling terms and uses contributes to substantial misunderstanding by industry and consumers and leads to significant unnecessary food loss and waste, misapplication of limited resources, unnecessary financial burden for the consumer and the food industry, and may also lead to potential food safety risk in regards to perishable foods. A use by or similar date cannot be relied on to indicate or guarantee food safety because absolute temperature control of food products throughout the food supply chain cannot be assured. This paper provides an introduction to the issue of food product date labeling and addresses its history in the United States, different terms used and various practices, U.S. and international frameworks, quality compared with safety, adverse impacts of misconceptions about date labeling, and advantages of technological innovations. Collaboration to develop a simple workable solution to address the challenges faced by stakeholders would have tremendous benefit. Conclusions include a call to action to move toward uniformity in date labeling, thereby decreasing confusion among stakeholders and reducing food waste.

Rapid detection of ricin in milk using immunomagnetic separation combined with surface-enhanced Raman spectroscopy.

UNLABELLEDnRicin is a potential bioterrisiom agent. There is a critical need for a method that can rapidly and simply detect ricin and other bioterrisiom agents in complex food matrices such as milk. In this study, we demonstrated a rapid method that combined immunomagnetic separation (IMS) and surface-enhanced Raman spectroscopy (SERS) to detect ricin in whole milk. IMS was used to specifically capture the ricin out of the milk. Then, SERS was applied to analyze the IMS eluate mixed with silver dendrite nanosubstrates. This approach facilitated detection and quantification down to 4 μg/mL ricin in milk within 20 min, based on the results of principal component analysis and partial least squares analysis. The feasibility of using a portable Raman instrument shows great promise for on-site detection in a processing facility.nnnPRACTICAL APPLICATIONnThe method described in this manuscript that combined IMS and SERS could be used for rapid detection of ricin and other protein toxins in complex food matrices such as milk within 20 min. The use of a portable Raman could facilitate the on-site detection in a processing facility.