Survival and growth behavior of common foodborne pathogens in falafel paste under different storage temperatures.

Falafel is a popular breakfast food in the Middle East that has been recently involved in several outbreaks of foodborne illnesses. The aim of the study was to explore the growth behavior of Salmonella enterica, Escherichia coli O157:H7, Shigella sonnie, Shigella flexneri, Listeria monocytogenes and Staphylococcus aureus in falafel paste (FP) under different storage temperatures (4, 10, or 24 °C) for 14 days. FP (pH = 6.2, aw = 0.96) was inoculated with 5.0 to 6.0 log CFU/g of each of the pathogens separately. Salmonella spp. significantly declined by 1.5 log at 4 °C but grew significantly by ca. 2 and 4 log at 10 and 24 °C, respectively after 14 days. E. coli O157:H7 significantly increased (4.5 log) in FP when stored under 24 °C and survived at a level of ~105 CFU/g at 10 °C. Comparatively, Sh. sonnie and Sh. flexneri showed a better survival pattern in FP stored under 4 °C and grew (˃ 3 log) after 5 days at 10 and 24 °C. L. monocytogenes was capable of growing by 1.9 and 4.3 log after 14 d days and by 3.9 log after 3 days at 4, 10, or 24 °C, respectively. No significant decline in S. aureus counts at 4 and 10 °C occurred, however, it increased significantly to ˃ 7 log CFU/g at 24 °C. Total mesophilic count and yeast and mold count reached to spoilage levels (˃107 CFU/g) in un-inoculated FP after 1 and 3 days of storage at 24 and 10 °C, respectively. FP could support the growth of common foodborne pathogens and hence it is recommended to utilize natural antimicrobials in FP and keep the product under refrigeration (4 °C) to preclude the growth of vegetative foodborne pathogens.

Heat-induced formation of advanced glycation end-products in ground pork as affected by the addition of acetic acid or citric acid and the storage duration prior to the heat treatments.

The heat-induced (121 °C, 10 or 30 min) formation of two potentially hazardous advanced glycation end-products (AGEs), protein-bound Nɛ -carboxymethyllysine (CML) and Nɛ -carboxyethyllysine (CEL), in pork as affected by citric or acetic acid (0.5, 1 g/100 pork) and the storage duration (0 °C, 0 - 8 d) prior to the heating was investigated. A longer storage time of raw pork resulted in higher levels of AGEs produced during the later heating, likely due to the accumulation of some AGE precursors during the storage. Depending on the acid level and heating time, adding acid in pork led to 30 - 54% (citric acid) or 14 - 48% (acetic acid) average reduction of heat-induced production of CML/CEL, which corresponded to the reduction of thiobarbituric acid reactive substances and Schiff bases. The marinating time of raw pork with an acid did not significantly affect (P = 0.959 - 0.998) the acid's inhibition effect on heat-induced formation of CML/CEL.

Smart traceability for food safety.

Current food production faces a tremendous challenge due to the growing human population. The global population is estimated to reach 9 billion by 2050 with 70% more food being required. Safe food is an important dimension of food security, and food traceability across the supply chain is a key component of this. However, current food traceability systems are challenged by frequent occurrences of food safety incidents and food recalls that have damaged consumer confidence, caused huge economic loss, and put pressure on food safety agencies. This review focuses on smart food traceability that has the potential to significantly improve food safety in global food supply chains. The basic concepts and critical perspectives for various detection strategies for food safety are summarized, including portable detection devices, smart indicators and sensors integrated on food packages, and data-assisted whole-genome sequencing. In addition, new digital technologies, such as Internet-of-things (IoTs) and cloud computing, are discussed with the aim of providing readers with an overview of the exciting opportunities in smart food traceability systems.

Formation of protein-bound Nε-carboxymethyllysine and Nε-carboxyethyllysine in ground pork during commercial sterilization as affected by the type and concentration of sugars.

This research was aimed to investigate the formation of protein-bound Nε-carboxymethyllysine (CML) and Nε-carboxyethyllysine (CEL) in ground pork at 121 °C (5-30 min) as affected by sugars (1-9% w/w, glucose, fructose, lactose, and sucrose).The addition of reducing sugar significantly (P < 0.05) increased the levels of CML and CEL in heat treated pork samples. Even adding 1% of glucose in pork could lead to 3.8 and 4.0 times increase in the formation rate constant (zero-order) of CML and CEL, respectively. In a typical commercial sterilization process (121 °C, 30 min), adding glucose, fructose or lactose in pork resulted in an average increase of 224-581%, 26-276%, and 8-189% CML, and 217-720%, 213%-15.8 times, and 20-150% CEL, respectively, depending on the sugar concentration. Sucrose did not promote the formation of CML and CEL in pork during heating.

Trace analysis of organic compounds in foods with surface-enhanced Raman spectroscopy: Methodology, progress, and challenges.

Surface-enhanced Raman spectroscopy (SERS) provides a potential solution for rapid analysis of trace compounds such as residual pesticides, naturally occurred toxicants, banned or restricted drugs, and food additives in complex food matrices. In this review, the basic principles of SERS and general approaches to successfully apply SERS in food analysis are covered from an applications perspective. The key steps including substrate selection and evaluation, sample preparation and simplification, spectral collection, and data analysis during the development of SERS methods for food analysis are summarized, together with the discussion of typical underlying technical barriers or major challenges of these methods and their applications. Future directions in successfully applying SERS technology as a routine analytical approach to solve real-world food problems are analyzed. This comprehensive review summarizes the recent progress on theory, application, and scope of SERS for food analysis, providing a basic understanding of the technology; more importantly, key methodology, potential pitfalls, and possible solutions during the development of rapid SERS methods based on authors' years of SERS experience are shared with researchers in the field.

Fiber-Rich Food Processing Byproducts Enhance the Expansion of Cornstarch Extrudates.

Expansion characteristics of cornstarch-based extrudates incorporating fiber-rich food processing byproducts was explored. Waxy and regular cornstarch were used as the base materials with apple pomace and sugarcane bagasse incorporated at two addition levels (0%, 15%, and 30% w/w). Extrusions were conducted at three different screw speeds (150, 200, and 250 rpm) with other parameters optimized and kept constant. Apple pomace inclusion resulted in higher initial expansion index (4.23 to 5.60) and higher stable expansion index (2.76 to 4.43), but also showed higher shrinkage (8.50% to 34.72%) than sugarcane bagasse extrudates at the same inclusion levels. Inclusion of apple pomace showed potential of producing extrudates with significantly higher expansion than cornstarch control, with relatively lower energy inputs. Extrusion methods used here have the potential to preserve the textural quality and nutritional value of the fiber-enriched extrudates, providing the base for healthier snack food items. PRACTICAL APPLICATION: Findings from this study can be extended to the other fiber-rich food processing byproducts, such as other fruit and vegetable pomace, cereal brans, and pulse hulls among other materials. This data will help the development of fiber-enriched extruded snacks that would have favorable consumer traits.

Combination effects of salts and cold storage on the formation of protein-bound Nɛ-(carboxymethyl)lysine and Nɛ-(carboxyethyl)lysine in raw and subsequently commercially sterilized ground pork.

The effects of cold storage (0 °C, 0-8 days) and salts (NaCl, 0.5-5%; NaNO2, 50-150 mg/kg) on the formation of protein-bound Nɛ-(carboxymethyl)lysine (CML) and Nɛ-(carboxyethyl)lysine (CEL) in raw and subsequently commercially sterilized (121 °C, 10 min) pork were investigated. Based upon two-factor analysis of variance (α = 0.05), there was no significant interaction effect between salts and storage time on the levels of CML and CEL in raw or sterile pork; salts and storage time did not significantly affect the amounts of CML and CEL in raw pork. However, in sterile pork, 1.5-5% NaCl treatments led to an average of 7.5-52.6% increase in CML, while NaNO2 resulted in 25.4-37.1% and 21.4-23.4% reduction in CML and CEL, respectively; raw pork stored for 8 days led to 82.5% increase of CML and 32.6% increase of CEL in the sterile products (n = 30), as compared to those without cold storage.

Gold Nanorods as Surface-Enhanced Raman Spectroscopy Substrates for Rapid and Sensitive Analysis of Allura Red and Sunset Yellow in Beverages.

Synthetic colorants in food can be a potential threat to human health. In this study, surface-enhanced Raman spectroscopy (SERS) coupled with gold nanorods as substrates is proposed to analyze allura red and sunset yellow in beverages. The gold nanorods with different aspect ratios were synthesized, and their long-term stability, SERS activity, and the effect of the different salts on the SERS signal were investigated. The results demonstrate that gold nanorods have a satisfactory stability (stored up to 28 days). SERS coupled with gold nanorods exhibit stronger sensitivity. MgSO4 was chosen to improve the SERS signal of sunset yellow, and no salts could enhance the SERS signal of allura red. The lowest concentration was 0.10 mg/L for both colorant standard solutions. The successful prediction results using SERS were much closer to those obtained by high-performance liquid chromatography for the sample in beverages. SERS combined with gold nanorods shows potential for analyzing food colorants and other food additives as a rapid, convenient, and sensitive method.

Composition and Physicochemical Characterization of Fiber-Rich Food Processing Byproducts.

A wide range of fiber-rich food processing byproducts from various sources have been proposed as value-added ingredients for producing healthier food products. Characterizing their composition and physicochemical properties is crucial to understand their potential uses. Eight fiber-rich byproducts from different sources were fractionated into 2 different particle-size ranges. Different (P ≤ 0.05) proximate composition and physicochemical properties (pasting properties, water-binding capacity, and oil-binding capacity) were exhibited by them. These properties enabled hierarchical cluster analysis and principal component analysis to group the byproducts into 3 different clusters by functionality and from this, assigned ingredients in each cluster to a potential end-uses. Some end use examples include, as a source of fat, protein, sugar, and insoluble fiber; and for uses as a thickening agent, water-binder, emulsion-enhancer, and fat-binder. PRACTICAL APPLICATION: The data presented in this study can be used by food manufacturers and product developers as the basis for choosing fiber-rich byproducts for specific applications and assist them in developing specific formulation and processing strategies. This characterization will reduce the time for development of fiber-rich foods, increasing industrial uses of byproducts, and decreasing food waste.

Rapid and sensitive surface-enhanced Raman spectroscopy (SERS) method combined with gold nanoparticles for determination of paraquat in apple juice.

BACKGROUND: Paraquat, a highly efficient herbicide, is widely used in agricultural practices throughout the world. However, paraquat residues in food pose a threat to human health. In order to develop a rapid and sensitive method, surface-enhanced Raman spectroscopy (SERS) coupled with gold nanoparticles was applied to analysis of paraquat in apple juice. RESULTS: Natural organic compounds (sugars and organic acids) in apple juice interfered with SERS measurement. Sample preparation was needed. Paraquat could be detected at concentrations as low as 0.02 and 0.1 µg mL- 1 with the weak cation-exchange solid-phase extraction (WCX-SPE) method and dilution method for sample preparation, respectively. For quantitative analysis, the R2 cv of the partial least-squares regression model with the dilution method (0.939) was not as good as with the WCX-SPE method (0.984), but the dilution method is much less costly, simpler and time saving. Satisfactory recovery values were obtained ranging from 94.73% to 114.81%, with the exception of 56.55% for the lowest concentration. CONCLUSION: This work showed that SERS combined with gold nanoparticles could determine paraquat in apple juice. As a simple, rapid and ultrasensitive method, it has great practical potential for detection of other contaminants in a variety of foods. © 2018 Society of Chemical Industry.

Rheological and sensory behaviors of parboiled pasta cooked using a microwave pasteurization process.

Pasta hydration and cooking requirements make in-package microwave pasteurization of pasta a processing challenge. The objective of this study was to assess instrumental and sensory attributes of microwave-treated pasta in comparison to conventionally cooked pasta. Fettuccine pasta was parboiled for 0, 3, 6, 9, or 12 min, pasteurized by microwaves at 915 MHz, then stored under refrigeration for 1 week. Pastas were evaluated by a trained sensory panel and with rheometry. Total pasta heat treatment affected both rheological and sensory behaviors; these differences were attributed to ultrastructure differences. Significant nonlinear behavior and dominant fluid-like behavior was observed in all pastas at strains >1%. Sensory results suggested microwave pasteurization may intensify the attributes associated with the aging of pasta such as retrogradation. A clear trend between magnitude of heat treatment and attribute intensity was not observed for all sensory attributes tested. The microwave pasta with the longest parboil time showed rheological behavior most similar to conventionally cooked pasta. Principal component analysis revealed that no microwave-treated pasta was similar to the control pasta. However, pasta parboiled for 9 min before microwave treatment had the greatest number of similar sensory attributes, followed by pasta parboiled for 6 or 12 min. Further study is needed to determine overall consumer acceptance of microwave-treated pasta and whether the differences in sensory and rheological behavior would impact consumer liking. PRACTICAL APPLICATIONS: The results of this study may be applied to optimize microwave pasteurization processes for cooked pasta and similar products, such as rice. The measurement and analysis procedures can be used to evaluate processing effects on a variety of different foods to determine overall palatability.

Inhibition of Shigella sonnei and Shigella flexneri in Hummus Using Citric Acid and Garlic Extract.

Hummus (chickpea dip) is a ready-to-eat product that may pose a significant risk to human if pathogens are present. Several organisms including Shigella spp. have been isolated from hummus. However, studies on the survival and inhibition of Shigella spp. in food are scarce. This study investigated the growth pattern of Sh. sonnei and Sh. flexneri in hummus at different temperatures (4, 10, and 24 °C). Additionally, the inhibitory activity of different concentrations of citric acid (CA) (0.5%, 1.0%, and 2.0%) and garlic extract (GE) (1.0%, 2.0%, and 3.0%) against Sh. sonnei and Sh. flexneri inoculated into hummus and stored at 4 and 10 °C was investigated. Both Shigella spp. survived well at 4 °C, while both grew to >7.0 log10 after 4 d at 10 °C or 1 d at 24 °C. At 4 °C, CA at 0.5% and 1.0% resulted in a slight reduction in the count (approximately 1.0 log10 ); a complete elimination of Sh. sonnei was attained by using 2.0% CA. However, approximately 3.0 log10 reduction in Sh. sonnei was obtained at 10 °C. For Sh. flexneri, CA at 0.5% and 1.0% resulted in a bacteriostatic inhibition. GE at 1.0% and 2.0% resulted in approximately 1.0 to 2.0 log10 reduction in Sh. sonnei count at 4 °C, while at 3.0% GE, approximately 4.0 and 3.0 log10 reductions were obtained at 4 and 10 °C, respectively. In comparison, the 2.0% and 3.0% GE resulted in a bacteriostatic effect against Sh. flexneri at 4 and 10 °C.

Microwave Pasteurization of Cooked Pasta: Effect of Process Parameters on Texture and Quality for Heat-and-Eat and Ready-to-Eat Meals.

Pasta presents a challenge to microwave processing due to its unique cooking requirements. The objective of this study was to determine the effects of microwave processing on pasta physicochemical and mechanical properties. Fettuccine pasta was parboiled for selected times, then pasteurized using a Microwave Assisted Pasteurization System and stored under refrigeration for 1 wk. Samples were analyzed using microscopy, mechanical testing, and chemical analyses after storage. While no significant differences were observed for free amylose among fresh samples, samples parboiled for ≤6 min had significantly higher free amylose, suggesting reduced starch retrogradation. Increased heat treatment increased degree of protein polymerization, observed in microstructures as increased gluten strand thickness and network density. Firmness and extensibility increased with increased parboil time; however, extension data indicated an overall weakening of microwave-treated pasta regardless of total cooking time. Overall, microwave pasteurization was shown to be a viable cooking method for pasta.

Ultraviolet-C Light Sanitization of English Cucumber (Cucumis sativus) Packaged in Polyethylene Film.

Food safety is becoming an increasing concern in the United States. This study investigated the effects of ultraviolet-C (UV-C) light as a postpackaging bactericidal treatment on the quality of English cucumber packaged in polyethylene (PE) film. Escherichia coli k-12 was used as a surrogate microbe. The microbial growth and physical properties of packaged cucumbers were analyzed during a 28-d storage period at 5 °C. Inoculating packaged cucumbers treated at 23 °C for 6 min with UV-C (560 mJ/cm(2) ) resulted in a 1.60 log CFU/g reduction. However, this treatment had no significant effect (P > 0.05) on the water vapor transmission rate or oxygen transmission rate of the PE film. Results show that UV-C light treatment delayed the loss of firmness and yellowing of English cucumber up to 28 d at 5 °C. In addition, UV-C light treatment extended the shelf life of treated cucumber 1 wk longer compared to untreated cucumbers. Electron microscopy images indicate that UV-C light treatment influences the morphology of the E. coli k-12 cells. Findings demonstrate that treating cucumbers with UV-C light following packaging in PE film can reduce bacterial populations significantly and delay quality loss. This technology may also be effective for other similarly packaged fresh fruits and vegetables.

Formation of free and protein-bound carboxymethyllysine and carboxyethyllysine in meats during commercial sterilization.

The effect of commercial sterilization treatments on the levels of advanced glycation endproducts (AGEs) in meats was investigated. The amounts of both free and protein-bound N(ε)-carboxymethyllysine (CML) and N(ε)-carboxyethyllysine (CEL) in beef (rump, ribeye, short plate), pork (hind leg, tenderloin, belly), and chicken (chicken breasts, drumsticks) were determined using an HPLC-MS/MS method. Beef and pork had a small proportion (raw <15%; sterilized <8%) of free AGEs compared to the total AGEs, but raw chicken breasts had very high levels of free CEL (7.12±9.98 mg/kg; n=13) with large biological variation compared to pork (0.19±0.09 mg/kg; n=9) and beef (0.44±0.19 mg/kg; n=9). Commercial sterilization (121°C for 10 min) did not significantly affect the amounts of free CML or CEL, but led to about 0.6- to 3.6-fold increase of protein-bound CML and CEL. The amounts of protein and fat content in beef or pork had very little effect on the formation of protein-bound AGEs during sterilization process.

Detection of Prohibited Fish Drugs Using Silver Nanowires as Substrate for Surface-Enhanced Raman Scattering.

Surface-enhanced Raman scattering or surface-enhanced Raman spectroscopy (SERS) is a promising detection technology, and has captured increasing attention. Silver nanowires were synthesized using a rapid polyol method and optimized through adjustment of the molar ratio of poly(vinyl pyrrolidone) and silver nitrate in a glycerol system. Ultraviolet-visible spectrometry, X-ray diffraction, and transmission electron microscopy were used to characterize the silver nanowires. The optimal silver nanowires were used as a SERS substrate to detect prohibited fish drugs, including malachite green, crystal violet, furazolidone, and chloramphenicol. The SERS spectra of crystal violet could be clearly identified at concentrations as low as 0.01 ng/mL. The minimum detectable concentration for malachite green was 0.05 ng/mL, and for both furazolidone and chloramphenicol were 0.1 µg/mL. The results showed that the as-prepared Ag nanowires SERS substrate exhibits high sensitivity and activity.

Influence of Xanthan-Curdlan Hydrogel Complex on Freeze-Thaw Stability and Rheological Properties of Whey Protein Isolate Gel over Multiple Freeze-Thaw Cycle.

UNLABELLED: The effect of adding xanthan-curdlan hydrogel complex (XCHC) at 2 concentrations (0.25 and 0.5% w/w) on the freeze-thaw stability of heat-induced whey protein isolate (WPI) gel was investigated. Samples were stored at 4 °C for 24 h before subjected to 5 freeze-thaw cycles alternating between -16 °C (18 h) and 25 °C (6 h). Adding XCHC to the WPI solution resulted in the reduction of a significant amount of syneresis up to 5 repeated freeze-thaw cycles. Addition of XCHC decreased the amount of syneresis from 45% in the control sample (pure WPI gel) to 31.82% and 5.44% in the samples containing 0.25% and 0.5% gum, respectively, after the 5th freeze-thaw cycle. XCHC increased the storage modulus (G') of the gels and minimized the changes of the G' values over the 5 freeze-thaw cycles, indicating improvement of the stability of the system. Furthermore, the minimum protein concentration for gel formation decreased in the presence of the XCHC. Scanning electron microscopy (SEM) images showed that addition of XCHC resulted in the formation of a well-structured gel with numerous small pores in the network, which consequently improved the water retention ability during the temperature abuses up to 5 freeze-thaw cycles. These results have important implications for using XCHC in the formulation of the frozen WPI-based products with improved freeze-thaw stability and rheological properties. PRACTICAL APPLICATION: Application of XCHC in the formulation of frozen dairy-based food products has the potential to enhance freeze-thaw stability and minimize moisture migration caused by temperature abuses of the products during distribution and consumer application.

Effect of marination in gravy on the radio frequency and microwave processing properties of beef.

Dielectric properties (the dielectric constant (ε') and the dielectric loss factor (ε″)) and the penetration depth of raw eye of round beef Semitendinosus muscle, raw beef marinated in gravy, raw beef cooked in gravy, and gravy alone were determined as a function of the temperature (20-130 °C) and frequency (27-1,800 MHz). Both ε' and ε″ values increased as the temperature increased at low frequencies (27 and 40 MHz). At high frequencies (915 and 1,800 MHz), ε' showed a 50 % decrease while ε″ increased nearly three fold with increasing temperature in the range from 20 to 130 °C. ε' increased gradually while ε″ increased five fold when the temperature increased from 20 to 130 °C. Both ε' and ε″ of all samples decreased with increase in frequency. Marinating the beef in gravy dramatically increased the ε″ values, particularly at the lower frequencies. Power penetration depth of all samples decreased with increase temperature and frequency. These results are expected to provide useful data for modeling dielectric heating processes of marinated muscle food.

Formation of advanced glycation endproducts in ground beef under pasteurisation conditions.

Advanced glycation endproducts (AGEs) in food products may pose health risks, and thermal processing of foods accelerates the formation of AGEs. The effects of heat treatments (65-100 °C, 0-60 min) on the formation of AGEs including N(ε)-carboxymethyllysine (CML) and N(ε)-carboxyethyllysine (CEL) in ground beef were investigated. The levels of CML and CEL in ground beef steadily increased with heating time and heating temperature. A strong linear relationship (r(2) = 0.920) between the amounts of CML (2.76-19.96 mg/kg) and CEL (2.32-11.89 mg/kg) in raw and thermally treated beef was found. The formations of both CML and CEL in ground beef during heat treatments basically fitted zero-order reactions (CML: r(2) = 0.851-0.995, rate constant = 0.031-0.224 mg kg(-1) min(-1); CEL: r(2) = 0.907-0.971, rate constant = 0.044-0.118 mg kg(-1) min(-1)) with an activation energy of 61.01 kJ/mol for CML and 29.21 kJ/mol for CEL.

Rapid analysis of malachite green and leucomalachite green in fish muscles with surface-enhanced resonance Raman scattering.

Surface-enhanced resonance Raman scattering (SERRS) coupled with gold nanospheres was applied for rapid analysis of the hazardous substances malachite green (MG) and leucomalachite green (LMG) in fish muscle tissues. The lowest concentration of MG that could be detected was 0.5ngmL(-1) with high linear correlation (R(2)=0.970-0.998) between MG concentration and intensities of characteristic Raman peaks. A simplified sample preparation method taking less than 1h for recovering MG and LMG in fish fillets was developed for SERRS analysis, and 4-8 samples could be handled in parallel. MG and LMG could be detected in extracts of tilapia fish fillets at as low as 2ngg(-1) with SERRS and a simple principle component analysis method. For six other fish species, the lowest detectable concentration of MG ranged from 1ngg(-1) to 10ngg(-1). This study provides a new sensitive approach for the detection of trace amounts of the prohibited drugs MG and LMG in muscle food, which has the potential for rapidly screening a large number of samples.