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Dong Y, Shen Y, Ge D, Bian C, Yuan H, Zhu N. A sodium dichloroisocyanurate-based conditioning process for the improvement of sludge dewaterability and mechanism studies. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2021; 284:112020. [PMID: 33508699 DOI: 10.1016/j.jenvman.2021.112020] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Revised: 01/16/2021] [Accepted: 01/17/2021] [Indexed: 06/12/2023]
Abstract
Sludge dewatering is necessary to reduce the volume of sludge for cost-effective transport and ultimate disposal. In this study, a novel combined chemical conditioning process was proposed to improve sludge dewatering performance in which sludge flocs were destructed by sodium dichloroisocyanurate (DCCNa) and re-flocculated by Al2(SO4)3 and the mechanism was elucidated. The results showed that sludge capillary suction time (CST) dropped to 15.4 s and moisture content of dewatered sludge cake (Mc) deceased to 71.01% respectively, after the application of combined conditioning with the optimal dosage of 200 mg DCCNa/g dry solids (DS) and 80 mg Al2(SO4)3/g DS. With chemical conditioning, sludge physicochemical properties were greatly changed. With the DCCNa application, the percentage of low-molecular-weight substances in soluble extracellular polymeric substances (S-EPS) increased. Also, the sludge zeta potential dropped from -16.85 mV to -25.45 mV and the median particle size (D50) decreased from 54.1 μm to 51.6 μm. However, the subsequent conditioning by Al2(SO4)3 dosing not only led to an increment of 18% in the portion of macromolecules in S-EPS, but also increased the zeta potential and D50 to -10.74 mV and 53.2 μm, respectively. The bound water content in sludge declined from 2.92 g/g DS to 1.98 g/g DS after combined conditioning. We concluded that DCCNa disintegrated the sludge flocs and microbial cells leading to the release of bound water, fine particles and organic substances with negative charge, and the fine colloidal particles can be flocculated into large dense aggregations with the dosing of Al2(SO4)3. In summary, the proposed combined conditioning provided a highly effective and environmental friendly approach to improve the sludge dewatering performance.
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Affiliation(s)
- Yanting Dong
- School of Environmental Science & Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Yanwen Shen
- School of Environmental Science & Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Dongdong Ge
- School of Environmental Science & Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Chang Bian
- School of Environmental Science & Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Haiping Yuan
- School of Environmental Science & Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Nanwen Zhu
- School of Environmental Science & Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai, 200092, China.
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Sant'Anna PB, de Melo Franco BD, Maffei DF. Microbiological safety of ready-to-eat minimally processed vegetables in Brazil: an overview. JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE 2020; 100:4664-4670. [PMID: 32329100 DOI: 10.1002/jsfa.10438] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Revised: 04/07/2020] [Accepted: 04/24/2020] [Indexed: 06/11/2023]
Abstract
The market of ready-to-eat minimally processed vegetables (RTE-MPV) is increasing in Brazil and many other countries. During processing, these vegetables go through several steps that modify their natural structure while maintaining the same nutritional and sensory attributes as the fresh produce. One of the most important steps is washing-disinfection, which aims to reduce the microbial load, prevent cross-contamination and inactivate pathogenic microorganisms that may be present. Nonetheless, the presence of pathogens and occurrence of foodborne illnesses associated with consumption of RTE-MPV concern consumers, governments and the food industry. This review brings an overview on the microbiological safety of RTE-MPV, focusing on Brazilian findings. Most of the published data are on detection of Salmonella spp. and Listeria monocytogenes, indicating that their prevalence may range from 0.4% to 12.5% and from 0.6% to 3.1%, respectively. The presence of these pathogens in fresh produce is unacceptable and risky, mainly in RTE-MPV, because consumers expect them to be clean and sanitized and consequently safe for consumption without any additional care. Therefore, proper control during the production of RTE-MPV is mandatory to guarantee products with quality and safety to consumers. © 2020 Society of Chemical Industry.
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Affiliation(s)
- Pedro B Sant'Anna
- Department of Biological Sciences, 'Luiz de Queiroz' College of Agriculture, University of Sao Paulo, Piracicaba, Brazil
| | - Bernadette Dg de Melo Franco
- Department of Food and Experimental Nutrition, Faculty of Pharmaceutical Sciences, University of Sao Paulo, Sao Paulo, Brazil
- Food Research Center (FoRC-CEPID), Sao Paulo, Brazil
| | - Daniele F Maffei
- Food Research Center (FoRC-CEPID), Sao Paulo, Brazil
- Department of Agri-food Industry, Food and Nutrition, 'Luiz de Queiroz' College of Agriculture, University of Sao Paulo, Piracicaba, Brazil
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Effects of Water Quality and Post-Harvest Handling on Microbiological Contamination of Lettuce at Urban and Peri-Urban Locations of Ouagadougou, Burkina Faso. Foods 2018; 7:foods7120206. [PMID: 30558351 PMCID: PMC6306915 DOI: 10.3390/foods7120206] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Revised: 12/11/2018] [Accepted: 12/12/2018] [Indexed: 12/04/2022] Open
Abstract
Vegetable production in urban gardens of Ouagadougou contributes to food security, but water for irrigation is often of low quality. This is particularly acute if irrigation water is taken from wastewater polluted channels. This study aimed at (i) verifying to what degree irrigation water quality is correlated with contamination of lettuce with Escherichia coli, total coliforms, and Salmonella spp., and (ii) assessing effects of post-harvest handling on pathogen development during the trade chain. We tested pathogen removal efficiency on lettuce by applying post-harvest washing. Irrigation water of production areas in Ouagadougou (n = 10) showed a mean E. coli load of 2.1 × 105 CFU 100 mL−1. In 60% of the cases, irrigation water did not meet the standards of the World Health Organization (WHO) for safe irrigation water, and in 30% of the cases, irrigation water was contaminated with Salmonella spp. Loads of total coliforms on lettuce leaves ranged from 2.9 × 103 CFU g−1 to 1.3 × 106 CFU g−1, while E. coli averaged 1.1 × 102 CFU g−1. Results on post-harvest handling revealed that microbial loads increased along the trade chain. Overall, half of all lettuce samples (n = 60) were tested positively for Salmonella spp. The experiment showed that appropriate post-harvest handling could prevent the increase of total coliforms.
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Ultrasound improves antimicrobial effect of sodium dichloroisocyanurate to reduce Salmonella Typhimurium on purple cabbage. Int J Food Microbiol 2018; 269:12-18. [DOI: 10.1016/j.ijfoodmicro.2018.01.007] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2017] [Revised: 11/22/2017] [Accepted: 01/06/2018] [Indexed: 11/20/2022]
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Silveira LO, do Rosário DKA, Giori ACG, Oliveira SBS, da Silva Mutz Y, Marques CS, Coelho JM, Bernardes PC. Combination of peracetic acid and ultrasound reduces Salmonella Typhimurium on fresh lettuce ( Lactuca sativa L. var. crispa). Journal of Food Science and Technology 2018; 55:1535-1540. [PMID: 29606768 DOI: 10.1007/s13197-018-3071-8] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Revised: 01/26/2018] [Accepted: 02/12/2018] [Indexed: 10/18/2022]
Abstract
Salmonella outbreaks related to fruits and vegetables have been reported being lettuce one of the most contaminated. Peracetic acid (PA) at 50 mg/L, sodium dichloroisocyanurate (SD) at 100 mg/L, and the combination of SD at 100 mg/L and babaçu coconut (Attalea speciosa) oil detergent at 100 mg/L were applied to fresh lettuce. Natural contaminant microbiota, physicochemical characteristics, and sensory attributes were evaluated. PA and SD reduced mesophilic aerobic counts by 2.1 and 1.5 log cfu/g, respectively. The most efficient treatment in reducing natural microbiota (i.e., PA) was applied alone and in combination with ultrasound (US). It reduced Salmonella enterica Typhimurium counts to undetectable levels (< 1 log cfu/g). US further reduced S. Typhimurium counts by 0.6 log cfu/g in relation to PA, treatment which lessened the pH but increased the titratable acidity of lettuce, but did not cause total color difference. Therefore, the combination of PA and US holds a potential industrial application for sanitization purposes.
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Affiliation(s)
- Luiza Oliveira Silveira
- 1Departamento de Engenharia de Alimentos, Universidade Federal do Espírito Santo, Alto Universitário, s/n, Alegre, ES 29500-000 Brazil
| | - Denes Kaic Alves do Rosário
- 2Programa de Ciência de Alimentos, Instituto de Química, Universidade Federal do Rio de Janeiro, Av. Athos da Silveira Ramos 149, Cidade Universitária, Rio de Janeiro, RJ 21941-909 Brazil
| | - Ana Carolina Garcia Giori
- 1Departamento de Engenharia de Alimentos, Universidade Federal do Espírito Santo, Alto Universitário, s/n, Alegre, ES 29500-000 Brazil
| | - Syllas Borburema Silva Oliveira
- 1Departamento de Engenharia de Alimentos, Universidade Federal do Espírito Santo, Alto Universitário, s/n, Alegre, ES 29500-000 Brazil
| | - Yhan da Silva Mutz
- 1Departamento de Engenharia de Alimentos, Universidade Federal do Espírito Santo, Alto Universitário, s/n, Alegre, ES 29500-000 Brazil
| | - Clara Suprani Marques
- 1Departamento de Engenharia de Alimentos, Universidade Federal do Espírito Santo, Alto Universitário, s/n, Alegre, ES 29500-000 Brazil
| | - Jussara Moreira Coelho
- 1Departamento de Engenharia de Alimentos, Universidade Federal do Espírito Santo, Alto Universitário, s/n, Alegre, ES 29500-000 Brazil
| | - Patrícia Campos Bernardes
- 1Departamento de Engenharia de Alimentos, Universidade Federal do Espírito Santo, Alto Universitário, s/n, Alegre, ES 29500-000 Brazil
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Song L, Luo H, Cheng X, Yan F, Yang Z, Yu Z. Effects of microwave treatment on physiology and quality of minimally processed bok choy (Brassica campestris L.) during storage at 5 °C. JOURNAL OF FOOD MEASUREMENT AND CHARACTERIZATION 2017. [DOI: 10.1007/s11694-017-9707-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Quantitative assessment of the impact of cross-contamination during the washing step of ready-to-eat leafy greens on the risk of illness caused by Salmonella. Food Res Int 2017; 92:106-112. [DOI: 10.1016/j.foodres.2016.12.014] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2016] [Revised: 12/18/2016] [Accepted: 12/23/2016] [Indexed: 11/22/2022]
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Microbiology of organic and conventionally grown fresh produce. Braz J Microbiol 2016; 47 Suppl 1:99-105. [PMID: 27825766 PMCID: PMC5156503 DOI: 10.1016/j.bjm.2016.10.006] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2016] [Accepted: 10/05/2016] [Indexed: 11/23/2022] Open
Abstract
Fresh produce is a generalized term for a group of farm-produced crops, including fruits and vegetables. Organic agriculture has been on the rise and attracting the attention of the food production sector, since it uses eco-agricultural principles that are ostensibly environmentally-friendly and provides products potentially free from the residues of agrochemicals. Organic farming practices such as the use of animal manure can however increase the risk of contamination by enteric pathogenic microorganisms and may consequently pose health risks. A number of scientific studies conducted in different countries have compared the microbiological quality of produce samples from organic and conventional production and results are contradictory. While some have reported greater microbial counts in fresh produce from organic production, other studies do not. This manuscript provides a brief review of the current knowledge and summarizes data on the occurrence of pathogenic microorganisms in vegetables from organic production.
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