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Alicyclobacillus spoilage and control - a review
(2020-01-02)
Pornpukdeewattana, Soisuda
;
Jindaprasert, Aphacha
;
Massa, Salvatore
In the last few decades Gram positive non pathogenic, rod shaped, thermo-acidophilic and acid-tolerant spore-forming bacteria such as Alicyclobacillus spp. have been identified as the causative agent in spoilage of commercially pasteurized fruit juice. In particular, A. acidoterrestris is considered a major producer of off-flavors. The spores of A. acidoterrestris possess the ability to survive commercial pasteurization processes, to germinate and grow in low pH environments and to produce volatile, unpleasant odorous compound (guaiacol) in fruit juices. The flat sour type of spoilage (without gas production or package swelling) is characterized as having a “medicinal,” “smoky,” and “antiseptic” off-flavor and makes the final juice product unacceptable. Spoilage by Alicyclobacillus is a major concern for producers since many of the new methods, which can destroy spores in the absence of chemical additives, may not destroy Alicyclobacillus. Although A. acidoterrestris is not pathogenic to humans, it can result in significant economic losses to juice processors because of its odor. The present review includes the taxonomy of Alicyclobacillus spp., their general characteristics, their resistance to heat and possible off-flavor production pathways. Particular emphasis is given to commonly used control measures, including physical, chemical and biological treatments currently available for removal of Alicyclobacillus spp.
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Upland rice vinegar vapor inhibits spore germination, hyphal growth and aflatoxin formation in Aspergillus flavus on maize grains
(2017-01-01)
Pornpukdeewattana, Soisuda
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Kerdpiboon, Soraya
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Jindaprasert, Aphacha
;
Pandee, Patcharaporn
;
Teerarak, Montinee
The efficacy of vapor-phase (VP) upland rice vinegar (URV) was investigated as a bio-fumigant for maize, to reduce consumer health risks associated with spore and toxin formation by Aspergillus flavus. Complete reduction of mycelial growth occurred with in vitro VP exposure to URV (containing 0.0017 mmol/L acetic acid) or with VP exposure to pure acetic acid (PAA) (containing 0.0023 mmol/L acetic acid). No significant differences were observed between the two materials after 90 min exposures. Using gas chromatography-mass spectrometry (GC-MS), URV vapor was shown to contain volatiles having antifungal activities. These are identified as isoamylalcohol, 1-butanol, 3-methyl-, acetate and β-phenylethyl acetate. It is suggested these volatiles increase the antifungal effectiveness of URV. Exposure to VP-URV (containing 0.0043 mmol/L AA) for 5 h completely eliminated viable spores of A. flavus on maize seeds (23% moisture content) previously inoculated with 4.43 ± 0.28 log spores/g). At the same time, aflatoxin production decreased, as VP-URV exposure increased. Hence, VP-URV is shown to be an effective control agent for A. flavus mycelial growth and aflatoxin formation on maize, so effectively reducing the potential for consumer health risks due to this widespread fungus.
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Lactic acid bacterial population dynamics during fermentation and storage of Thai fermented sausage according to restriction fragment length polymorphism analysis
(2014-09-01)
Wanangkarn, Amornrat
;
Liu, Deng Cheng
;
Swetwiwathana, Adisorn
;
Jindaprasert, Aphacha
;
Phraephaisarn, Chirapiphat
This study applied restriction fragment length polymorphism (RFLP) analysis to identify the lactic acid bacteria (LAB) isolated from "mum" Thai fermented sausages during fermentation and storage. A total of 630 lactic acid bacteria were isolated from the sausages prepared using 2 methods. In Method 1, after stuffing, the sausages were stored at 30. °C for 14. days. In Method 2, after stuffing and storage at 30. °C for 3. days, the sausages were vacuum-packed and stored at 4. °C until Day 28. The sausages were sampled on Days 0, 3, 14, and 28 for analyses. The 16S rDNA was amplified and digested using restriction enzymes. Of the restriction enzymes evaluated, Dde I displayed the highest discrimination capacity. The LAB were classified and 7 species were identified For Methods 1 and 2, during fermentation, the Lactobacillus sakei and Lactobacillus plantarum species were dominant. For Method 2, the proportion of Leuconostoc mesenteroides markedly increased during storage, until L. sakei and Ln. mesenteroides represented the dominant species. The identification of LAB in the sausage samples could facilitate the selection of appropriate microorganisms for candidate starter cultures for future controlled mum production. © 2014 Elsevier B.V.
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Simple densitometric TLC analysis of plaunotol for screening of high-plaunotol-containing plants of Croton stellatopilosus Ohba
(2009-02-01)
Rinthong, Prasob Orn
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Jindaprasert, Aphacha
;
De-Eknamkul, Wanchai
Plaunotol, an anti-peptic diterpenoid present in the leaves of Croton stellatopilosus Ohba, was separated from other components of crude methanolic extracts and quantified by densitometric TLC. Validation of precision, repeatability, and accuracy showed the technique was reliable, with 98.7% recovery of externally added plaunotol. Crude extracts of different leaf samples could be applied directly to silica gel TLC plates without prior sample preparation or concentration of the extracts. Plates were chromatographed with chloroform-n-propanol 96:4 (v/v) as mobile phase then scanned at 220 nm. The results showed that the plaunotol content of the leaves of C. stellatopilosus was highly variable (range 0.14 to 0.79% w/w of dry weight). Although most (35%) leaf samples seemed to contain 0.3-0.4% plaunotol, 8% contained more than 0.6%. This densitometric TLC method could, therefore, be a useful tool for screening of high-plaunotol-producing C. stellatopilosus plants as effective sources of the compound. © 2009 Akadémiai Kiadó.
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Pyrone polyketides synthesized by a type III polyketide synthase from Drosophyllum lusitanicum
(2008-12-01)
Jindaprasert, Aphacha
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Springob, Karin
;
Schmidt, Jürgen
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De-Eknamkul, Wanchai
;
Kutchan, Toni M.
To isolate cDNAs involved in the biosynthesis of acetate-derived naphthoquinones in Drosophyllum lusitanicum, an expressed sequence tag analysis was performed. RNA from callus cultures was used to create a cDNA library from which 2004 expressed sequence tags were generated. One cDNA with similarity to known type III polyketide synthases was isolated as full-length sequence and termed DluHKS. The translated polypeptide sequence of DluHKS showed 51-67% identity with other plant type III PKSs. Recombinant DluHKS expressed in Escherichia coli accepted acetyl-coenzyme A (CoA) as starter and carried out sequential decarboxylative condensations with malonyl-CoA yielding α-pyrones from three to six acetate units. However, naphthalenes, the expected products, were not isolated. Since the main compound produced by DluHKS is a hexaketide α-pyrone, and the naphthoquinones in D. lusitanicum are composed of six acetate units, we propose that the enzyme provides the backbone of these secondary metabolites. An involvement of accessory proteins in this biosynthetic pathway is discussed. © 2008 Elsevier Ltd. All rights reserved.

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