Editorial

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4 pages, 186 KiB

Open AccessEditorial

Editorial to Special Issue—Research on Isolation and Intelligent Detection Methods of Foodborne Pathogens

by Daohong Zhang and Jianlong Wang

Foods 2022, 11(9), 1213; https://0-doi-org.brum.beds.ac.uk/10.3390/foods11091213 - 22 Apr 2022

Cited by 1 | Viewed by 1130

Abstract

Foodborne illnesses pose a significant threat worldwide to public health [...] Full article

(This article belongs to the Special Issue Research on Isolation and Intelligent Detection Methods of Foodborne Pathogens)

Research

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14 pages, 2029 KiB

Open AccessArticle

Effects of 405 ± 5-nm LED Illumination on Environmental Stress Tolerance of Salmonella Typhimurium in Sliced Beef

by Du Guo, Yichen Bai, Shengyi Fei, Yanpeng Yang, Jiahui Li, Baowei Yang, Xin Lü, Xiaodong Xia and Chao Shi

Foods 2022, 11(2), 136; https://0-doi-org.brum.beds.ac.uk/10.3390/foods11020136 - 06 Jan 2022

Cited by 4 | Viewed by 1399

Abstract

Salmonella Typhimurium is a widely distributed foodborne pathogen and is tolerant of various environmental conditions. It can cause intestinal fever, gastroenteritis and bacteremia. The aim of this research was to explore the effect of illumination with 405 nm light-emitting diodes (LEDs) on the [...] Read more.

Salmonella Typhimurium is a widely distributed foodborne pathogen and is tolerant of various environmental conditions. It can cause intestinal fever, gastroenteritis and bacteremia. The aim of this research was to explore the effect of illumination with 405 nm light-emitting diodes (LEDs) on the resistance of S. Typhimurium to environmental stress. Beef slices contaminated with S. Typhimurium were illuminated by 405 nm LEDs (18.9 ± 1.4 mW/cm²) for 8 h at 4 °C; controls were incubated in darkness at 7 °C. Then, the illuminated or non-illuminated (control) cells were exposed to thermal stress (50, 55, 60 or 65 °C); oxidative stress (0.01% H₂O₂ [v/v]); acid stress (simulated gastric fluid [SGF] at pH 2 or 3); or bile salts (1%, 2%, or 3% [w/v]). S. Typhimurium treated by 405 nm LED irradiation showed decreased resistance to thermal stress, osmotic pressure, oxidation, SGF and bile salts. The transcription of eight environmental tolerance-related genes were downregulated by the illumination. Our findings suggest the potential of applying 405 nm LED-illumination technology in the control of pathogens in food processing, production and storage, and in decreasing infection and disease related to S. Typhimurium. Full article

(This article belongs to the Special Issue Research on Isolation and Intelligent Detection Methods of Foodborne Pathogens)

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15 pages, 18725 KiB

Open AccessArticle

Preparation and Characterization of Chitosan–Nano-ZnO Composite Films for Preservation of Cherry Tomatoes

by Yu Li, Yu Zhou, Zhouli Wang, Rui Cai, Tianli Yue and Lu Cui

Foods 2021, 10(12), 3135; https://0-doi-org.brum.beds.ac.uk/10.3390/foods10123135 - 17 Dec 2021

Cited by 26 | Viewed by 3750

Abstract

Chitosan is widely used as a natural preservative of fruits and vegetables, but its poor mechanical and water resistances have limited its application. Therefore, in this study, we prepared chitosan composite films by incorporating different amounts of nano-zinc oxide (nano-ZnO) to improve the [...] Read more.

Chitosan is widely used as a natural preservative of fruits and vegetables, but its poor mechanical and water resistances have limited its application. Therefore, in this study, we prepared chitosan composite films by incorporating different amounts of nano-zinc oxide (nano-ZnO) to improve the mechanical properties of chitosan. We also assessed the antibacterial activity of these films against selected microorganisms. The addition of nano-ZnO improved the tensile strength (TS) and elongation at break (EAB) of the chitosan films and reduced their light transmittance. TS and EAB increased from 44.64 ± 1.49 MPa and 5.09 ± 0.38% for pure chitosan film to 46.79 ± 1.65 MPa and 12.26 ± 0.41% for a 0.6% nano-ZnO composite film, respectively. The ultraviolet light transmittance of composite films containing 0.2%, 0.4%, and 0.6% nano-ZnO at 600 nm decreased from 88.2% to 86.0%, 82.7%, and 81.8%, respectively. A disc diffusion test showed that the composite film containing 0.6% nano-ZnO had the strongest antibacterial activity against Alicyclobacillus acidoterrestris, Staphylococcus aureus, Escherichia coli, and Salmonella. In a 15-day preservation study, chitosan composite films containing 0.6% nano-ZnO maintained the soluble solid content of cherry tomatoes, effectively inhibited their respiration, and exhibited good antibacterial properties against the selected microorganisms. Overall, the prepared chitosan nano-ZnO composite film showed a good preservation effect on cherry tomatoes. Full article

(This article belongs to the Special Issue Research on Isolation and Intelligent Detection Methods of Foodborne Pathogens)

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18 pages, 25375 KiB

Open AccessArticle

Antimicrobial Activity and Action Mechanism of Thymoquinone against Bacillus cereus and Its Spores

by Shuo Wang, Haichao Deng, Yihong Wang, Wushuang Rui, Pengyu Zhao, Qiyao Yong, Du Guo, Jie Liu, Xinyi Guo, Yutang Wang and Chao Shi

Foods 2021, 10(12), 3048; https://0-doi-org.brum.beds.ac.uk/10.3390/foods10123048 - 08 Dec 2021

Cited by 16 | Viewed by 3130

Abstract

In this study, thymoquinone (TQ), a natural active substance, was investigated for its antibacterial activity against Bacillus cereus, and its inhibitory effect on B. cereus in reconstituted infant formula (RIF) was evaluated. In addition, the inhibitory effect of TQ on B. cereus [...] Read more.

In this study, thymoquinone (TQ), a natural active substance, was investigated for its antibacterial activity against Bacillus cereus, and its inhibitory effect on B. cereus in reconstituted infant formula (RIF) was evaluated. In addition, the inhibitory effect of TQ on B. cereus spore germination was explored. The minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of TQ against eight B. cereus strains ranged from 4.0 to 8.0 μg/mL, whereas B. cereus treated with TQ displayed a longer lag phase than the untreated control. TQ exerted a good bactericidal effect on B. cereus in Luria–Bertani broth. In addition, TQ obviously reduced the intracellular ATP concentration of B. cereus, which caused depolarization of the cell membrane, increased the intracellular reactive oxygen species level, impaired the cell morphology, and destroyed proteins or inhibited proteins synthesis. This provides a mechanism for its bacteriostatic effect. TQ also inactivated B. cereus growth in RIF. Moreover, reverse transcription–quantitative polymerase chain reaction illustrated that TQ downregulated the transcription of genes related to hemolysin, non-hemolytic enterotoxin, enterotoxin, and cytotoxin K. Meanwhile, TQ displayed the ability to inhibit the germination of B. cereus spores. These findings indicate that TQ, as an effective natural antimicrobial preservative, has potential applications in controlling food contamination and foodborne diseases caused by B. cereus. Full article

(This article belongs to the Special Issue Research on Isolation and Intelligent Detection Methods of Foodborne Pathogens)

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14 pages, 1637 KiB

Open AccessArticle

Simultaneous Rapid Detection of Aflatoxin B₁ and Ochratoxin A in Spices Using Lateral Flow Immuno-Chromatographic Assay

by Xue Zhao, Xindi Jin, Zhang Lin, Qi Guo, Bin Liu, Yahong Yuan, Tianli Yue and Xubo Zhao

Foods 2021, 10(11), 2738; https://0-doi-org.brum.beds.ac.uk/10.3390/foods10112738 - 09 Nov 2021

Cited by 11 | Viewed by 2177

Abstract

Spices are susceptible to contamination by aflatoxin B₁ (AFB₁) and ochratoxin A (OTA), which are both mycotoxins with high toxicity and carcinogenicity. In this study, we aimed to develop an immuno-chromatographic strip test for the simultaneous quantification of AFB₁ [...] Read more.

Spices are susceptible to contamination by aflatoxin B₁ (AFB₁) and ochratoxin A (OTA), which are both mycotoxins with high toxicity and carcinogenicity. In this study, we aimed to develop an immuno-chromatographic strip test for the simultaneous quantification of AFB₁ and OTA in spices by spraying the coupled antigens AFB₁–ovalbumin (AFB₁–OVA) and OTA–ovalbumin (OTA–OVA) on a nitrocellulose membrane. The test strip had high sensitivity, good specificity, and strong stability. The detection limits of these two mycotoxins in Chinese prickly ash, pepper, chili, cinnamon, and aniseed were 5 μg/kg. The false positivity rate was 2%, and the false negativity rate was 0%. The maximum coefficient of variation was 4.28% between batches and 5.72% within batches. The average recovery rates of AFB₁ and OTA in spices were 81.2–113.7% and 82.2–118.6%, respectively, and the relative standard deviation (RSD) was <10%. The actual sample detection was consistent with high performance liquid chromatography analysis results. Therefore, the immuno-chromatographic test strips developed in this study can be used for the on-site simultaneous detection of AFB₁ and OTA in spices. This method would allow the relevant regulatory agencies to strengthen supervision in an effort to reduce the possible human health hazards of such contaminated spices. Full article

(This article belongs to the Special Issue Research on Isolation and Intelligent Detection Methods of Foodborne Pathogens)

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12 pages, 2671 KiB

Open AccessArticle

Natural Products Self-Assembled Nanozyme for Cascade Detection of Glucose and Bacterial Viability in Food

by Qiuping Zhang, Xinze Wang, Yi Kang, Hao Sun, Yanmin Liang, Jie Liu, Zehui Su, Jie Dan, Linpin Luo, Tianli Yue, Jianlong Wang and Wentao Zhang

Foods 2021, 10(11), 2596; https://0-doi-org.brum.beds.ac.uk/10.3390/foods10112596 - 27 Oct 2021

Cited by 10 | Viewed by 2387

Abstract

Sugar content and bacterial contamination levels are important indicators for the health and safety of food, respectively. Therefore, it is important to construct a method that can detect both glucose and bacterial activity. Herein, natural compounds (gallic acid and glucose oxidase) were assembled [...] Read more.

Sugar content and bacterial contamination levels are important indicators for the health and safety of food, respectively. Therefore, it is important to construct a method that can detect both glucose and bacterial activity. Herein, natural compounds (gallic acid and glucose oxidase) were assembled into nanozyme (GOx@GA-Fe (ii)) for mild cascade detection. The nanozyme catalyzes glucose to produce hydrogen peroxide, which is then converted to ·OH and oxidized colorless TMB from blue oxidized TMB. Under the optimal conditions, the method has a good linear relationship in the glucose concentration range of 1–500 μM (R² = 0.993) with minimum detection concentration of 0.43 μM. Based on the glucose consumption of bacteria metabolism, the cascade reaction was then applied to detect the viability of 5 common bacteria. As such, a cascade method based on a natural self-assembled nanozyme was fabricated to monitor the quality of food. Full article

(This article belongs to the Special Issue Research on Isolation and Intelligent Detection Methods of Foodborne Pathogens)

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10 pages, 1997 KiB

Open AccessCommunication

A Portable, Cost-Effective and User-Friendly Instrument for Colorimetric Enzyme-Linked Immunosorbent Assay and Rapid Detection of Aflatoxin B₁

by Wenzhi Tang, Yangchun Qi and Zhonghong Li

Foods 2021, 10(10), 2483; https://0-doi-org.brum.beds.ac.uk/10.3390/foods10102483 - 17 Oct 2021

Cited by 10 | Viewed by 2276

Abstract

Food analysis based on the enzyme-linked immunosorbent assay (ELISA) is simple, sensitive and rapid, but requires a costly colorimetric instrument. The aim of this work was to develop a portable, low-cost and user-friendly colorimetric instrument for colorimetric ELISA and aflatoxin B₁ (AFB [...] Read more.

Food analysis based on the enzyme-linked immunosorbent assay (ELISA) is simple, sensitive and rapid, but requires a costly colorimetric instrument. The aim of this work was to develop a portable, low-cost and user-friendly colorimetric instrument for colorimetric ELISA and aflatoxin B₁ (AFB₁) detection. The principle of the developed instrument was employing a light-emitting diode to generate the signal light and using a light-dependent resistor to measure the signal light absorbed by the oxidized 3,3′,5,5′-tetramethyl benzidine. The absorption spectra revealed that the solution absorbed signal light more strongly after reaction with H₂SO₄, and blue light would be favorably absorbed. Evaluations on the stability and accuracy of the instrument and interference from ambient light showed that the fabricated instrument was stable, accurate, capable of quantitative detection and insensitive to ambient light changes. In addition, this instrument is user-friendly since it could calculate and report the final amount of AFB₁ to the operator. Measurements of maize and peanuts showed that the instrument provided as accurate results as the professional equipment. With the low fabrication cost (about RMB 129 or USD 20), portability, and user-friendliness, this instrument presents attractive potential in the rapid detection of AFB₁. Full article

(This article belongs to the Special Issue Research on Isolation and Intelligent Detection Methods of Foodborne Pathogens)

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14 pages, 1849 KiB

Open AccessArticle

An Enhanced Lateral Flow Assay Based on Aptamer–Magnetic Separation and Multifold AuNPs for Ultrasensitive Detection of Salmonella Typhimurium in Milk

by Pingping Gao, Lihan Wang, Yang He, Yitian Wang, Xinyan Yang, Shiqian Fu, Xue Qin, Qing Chen, Chaoxin Man and Yujun Jiang

Foods 2021, 10(7), 1605; https://0-doi-org.brum.beds.ac.uk/10.3390/foods10071605 - 11 Jul 2021

Cited by 25 | Viewed by 3343

Abstract

In this paper, a novel and ultrasensitive lateral flow assay (LFA) based on aptamer–magnetic separation, and multifold Au nanoparticles (AuNPs) was developed for visual detecting Salmonella enterica ser. Typhimurium (S. Typhimurium). The method realized magnetic enrichment and signal transduction via magnetic separation [...] Read more.

In this paper, a novel and ultrasensitive lateral flow assay (LFA) based on aptamer–magnetic separation, and multifold Au nanoparticles (AuNPs) was developed for visual detecting Salmonella enterica ser. Typhimurium (S. Typhimurium). The method realized magnetic enrichment and signal transduction via magnetic separation and achieved signal amplification through hybridizing AuNPs–capture probes and AuNPs–amplification probes to form multifold AuNPs. Two different thiolated single-strand DNA (ssDNA) on the AuNPs–capture probe played different roles. One was combined with the AuNPs–amplification probe on the conjugate pad to achieve enhanced signals. The other was connected to transduction ssDNA1 released by aptamer–magnetic capture of S. Typhimurium, and captured by the T-line, forming a positive signal. This method had an excellent linear relationship ranging from 8.6 × 10² CFU/mL to 8.6 × 10⁷ CFU/mL with the limit of detection (LOD) as low as 8.6 × 10⁰ CFU/mL in pure culture. In actual samples, the visual LOD was 4.1 × 10² CFU/mL, which did not carry out nucleic acid amplification and pre-enrichment, increasing three orders of magnitudes than unenhanced assays with single–dose AuNPs and no magnetic separation. Furthermore, the system showed high specificity, having no reaction with other nontarget strains. This visual signal amplificated system would be a potential platform for ultrasensitive monitoring S. Typhimurium in milk samples. Full article

(This article belongs to the Special Issue Research on Isolation and Intelligent Detection Methods of Foodborne Pathogens)

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Review

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24 pages, 2631 KiB

Open AccessReview

Overview of Rapid Detection Methods for Salmonella in Foods: Progress and Challenges

by Minglu Wang, Yilun Zhang, Fangyuan Tian, Xiaoyu Liu, Shuyuan Du and Guocheng Ren

Foods 2021, 10(10), 2402; https://0-doi-org.brum.beds.ac.uk/10.3390/foods10102402 - 11 Oct 2021

Cited by 23 | Viewed by 5510

Abstract

Salmonella contamination in food production and processing is a serious threat to consumer health. More and more rapid detection methods have been proposed to compensate for the inefficiency of traditional bacterial cultures to suppress the high prevalence of Salmonella more efficiently. The contamination [...] Read more.

Salmonella contamination in food production and processing is a serious threat to consumer health. More and more rapid detection methods have been proposed to compensate for the inefficiency of traditional bacterial cultures to suppress the high prevalence of Salmonella more efficiently. The contamination of Salmonella in foods can be identified by recognition elements and screened using rapid detection methods with different measurable signals (optical, electrical, etc.). Therefore, the different signal transduction mechanisms and Salmonella recognition elements are the key of the sensitivity, accuracy and specificity for the rapid detection methods. In this review, the bioreceptors for Salmonella were firstly summarized and described, then the current promising Salmonella rapid detection methods in foodstuffs with different signal transduction were objectively summarized and evaluated. Moreover, the challenges faced by these methods in practical monitoring and the development prospect were also emphasized to shed light on a new perspective for the Salmonella rapid detection methods applications. Full article

(This article belongs to the Special Issue Research on Isolation and Intelligent Detection Methods of Foodborne Pathogens)

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