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Subject: search.filters.subject.Organic acids

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    Biocontrol of Listeria monocytogenes ATCC 7644 on fresh-cut tomato (Lycopersicon esculentum) using nisin combined with organic acids
    (The Korean Society of Food Science and Technology, 2015) Oladunjoye, Adebola Olubukola; Singh, Suren; Ijabadeniyi, Oluwatosin Ademola
    The biocontrol of Listeria monocytogenes on fresh-cut tomato using nisin and organic acids was investigated. Fresh-cut samples inoculated with 108 CFU/mL of L. monocytogenes, treated with nisin (5,000 IU/mL), a combination of nisin and organic acids (acetic and citric acids at 3 and 5% each), with chlorine at 200 ppm as a control, and stored for six days at 4, 10, and 25oC were used to evaluate certain physicochemical qualities (pH, titratable acidity, soluble solid content, vitamin C content, and color). Nisin treatment significantly (p<0.05) reduced bacterial population by 1.91-3.07 log CFU/mL. Nisin-citric acid combination provided 2.65-3.29 log CFU/mL reduction, while nisin-acetic acid combination provided 2.93-4.15 log CFU/mL reduction. The control treatment provided <1-2 fold log reductions. Slight variations in physicochemical properties of fresh-cut tomato were observed. Nisin and organic acids can be used to improve the microbial safety of fresh-cut tomato.
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    Production of levulinic acid from sugarcane bagasse
    (2016) Mthembu, Lethiwe Debra; Deenadayalu, Nirmala; Reddy, P.
    The main aim of this work was to produce levulinic acid (LA) from sugarcane bagasse (SB) and since there is approximately 3 000 000 tons of bagasse produced per annum by 16 factories that are located on the north coast of Kwa-Zulu Natal, after the extraction of sugar. For this project fructose was firstly used for the production of LA, thereafter SB was used to produce LA. Cellulose was extracted from sugarcane bagasse using two types of pre-treatments namely (i) acid-alkali pre-treatment and (ii) liquid hot water (LHW). In the latter method acid hydrolysis and enzymatic hydrolysis was used to hydrolyse cellulose to glucose. For the acid-alkali pre-treatment work, two types of bagasse was used namely (i) mill-run bagasse and (ii) depithed bagasse and for the LHW a mill-run bagasse (pellets form) was used. In both pre-treatment methods the glucose solution was then acid catalysed by two different acids (i) an environment friendly acid, methanesulfonic acid (MSA) and (ii) sulphuric acid, producing levulinic acid. The results showed that MSA and sulphuric acid produced almost the same yield of LA but, MSA is preferred for the production of LA since it is less toxic and less corrosive than sulphuric acid.
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    Detection methods of organic acid in steam/water circuits and optimisation using HPLC-UV
    (2009) Ramrung, Arthi; Moodley, Kandasamy Govindsamy; Chetty, Deenadayalan Kisten
    This study was mainly a response to a challenge faced by ESKOM in its coal-fired power stations. In spite of using high purity water to drive the turbines, the latter were damaged by ‘pitting’, possibly related to acids generated at high temperatures. In the light of this a relatively simple method for determination of short chain organic acids was identified by comparing the efficacies of several methods. It was found that high performance liquid chromatography (HPLC) method preceded by derivatization (with o-nitrophenyl hydrazine) is suitable for analyzing mixtures of simple acids at ppb levels. Calibration was effected by using methanoic acid (formic acid), ethanoic acid (acetic acid), propanoic acid (propionic acid) and butanoic acid (butyric acid). The HPLC instrument used was from Thermo Separations with P2000 pump, SN 4000 interface and UV1000 with a column heater. A comparative study between the HPLC methods using ion exclusion and partition chromatography was carried out in order to find a suitable method that can be used with aqueous environmental samples. The two essential columns that were used were ion exclusion Phenomenex Rezex OA column and a Nucleodur C8 column. The method of partition chromatography using a C8 column showed the most success using a mobile phase consisted of acidified water using HCl (pH4.5) along with a 60:40 Acetonitrile/Methanol mixture. Both isocratic and gradient programs were utilized. Limits of detection were improved from 800ppb (formic acid), 480ppb (acetic), 350ppb (propionic) and 680ppb (butyric acid) to 25ppb (acetic), 60ppb (propionic) and 90ppb (butyric). Samples used in analysis were collected from the main stream, economiser, condensers, polishing plant and turbines of the Tutuka Power Station in Mpumalanga province and analysed using with final developed method