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Evaluation of the distribution and accumulation of species of Alicyclobacillus in the fruit concentrate processing environment

Steyn, Catharina Elizabeth (2011-03)

Thesis (MSc Food Sc (Food Science))--University of Stellenbosch, 2011.

Includes bibliography.


ENGLISH ABSTRACT: Alicyclobacillus species are thermo-acidophilic bacteria that produce highly resistant endospores able to survive the processing temperatures of fruit concentrate manufacturing, including evaporation and conventional pasteurisation (86 ° - 96 °C for ± 2 min). Alicyclobacillus endospores retain their viability in juice concentrates which, under favourable conditions, could germinate and multiply to numbers high enough to cause spoilage and product deterioration through the production of chemical taint compounds. This thesis reports on the distribution of Alicyclobacillus in the fruit concentrate processing environment and the effect of current manufacturing practices on the accumulation of Alicyclobacillus in fruit concentrates. These practices include the recirculation (recycling) of flume water as a means of water conservation, as well as continuous process running times when facilities operate at full capacity. This thesis also reports on the effect of fruit variety and skin type on the occurrence of Alicyclobacillus in fruit concentrates. Alicyclobacillus was monitored at nine processing stages of fruit concentrate manufacturing during the functioning of either a recirculating or a one-pass (not recirculated) flume water system. Significantly higher Alicyclobacillus levels were recovered in fruit mash, single strength juice, concentrate and the final pasteurised product (± 30 °Brix) during the functioning of a re circulating flume system, compared to when a one-pass flume system was functional (P < 0.05). Irrespective of the flume system, high Alicyclobacillus levels were recovered from the concentrate and condensate water (a by-product of juice concentration) from the evaporator, which makes this a point of concern during concentrate manufacturing. Manufacturing practices such as the recirculation of flume water and the recovery of condensate water for fruit washing purposes pose a potential risk of Alicyclobacillus contamination and accumulation in fruit concentrates and the processing environment. The effect of continuous process running times on Alicyclobacillus was monitored in a facility that was operating at full capacity. Sampling occurred every 12 h at four processing stages, during a processing tempo of 1.8 - 2.0 t h-1 for 108 h. Vegetative cells increased significantly (P < 0.05) in single strength juice and condensate water after 84 h of processing, with 3.15 and 3.85 log10 cfu mL-1 recovered, respectively. Similar accumulation patterns of vegetative cells were observed in concentrate and the final pasteurised product. Endospores in single strength juice, concentrate and the final product were also the highest after 84 h of processing with 1.32, 1.59 and 1.64 log10 cfu mL-1, respectively. When fruit concentrate manufacturing facilities process at full capacity, a restriction in the continuous process running time to under 84 h in between CIP procedures, along with good manufacturing practices, can minimise Alicyclobacillus accumulation in fruit concentrates. The effect of fruit skin type, specifically hairy-skinned stone fruits (peach and apricot) and smooth-skinned pome fruits (apple and pear) on the occurrence of Alicyclobacillus in concentrates were examined. Apple concentrate samples had the highest occurrence (average %) of vegetative Alicyclobacillus cells (50%), followed by apricot (40%), peach (15%) and pear (10%) concentrates. The occurrence of Alicyclobacillus endospores in fruit concentrate samples were also the highest in apple (50%), followed by pear (25%), apricot (20%), and peach (10%) concentrates. The occurrence of Alicyclobacillus vegetative cells and endospores did not differ significantly (P > 0.05) between concentrates from hairy-skin and smooth-skin fruit varieties. Thus it was concluded that fruit washing steps prior to processing was more critical for the control of Alicyclobacillus than the type of fruit skin being processed.

AFRIKAANSE OPSOMMING: Alicyclobacillus spesies is termo-asidofiliese bakterieë wat hoogs bestande endospore produseer met die vermoë om prosesseringstemperature, insluitend verdamping en konvensionele pasteurisasie temperature (86 ° - 96 °C vir ± 2 min), tydens die vervaardiging van vrugtekonsentraat te oorleef. Alicyclobacillus endospore behou hul lewensvatbaarheid in vrugtekonsentrate en kan in gunstige toestande ontkiem en vermeerder tot getalle wat wansmake in produkte kan veroorsaak weens die produksie van chemiese verbindings. Hierdie tesis doen verslag oor die verspreiding van Alicyclobacillus in die vrugtekosentraat prosesseringsomgewing en oor die effek van huidige produksie praktyke op die akkumulasie van Alicyclobacillus in vrugtekonsentrate. Die praktyke sluit in, die hersirkulering van leigeut (transport) water as ‘n wyse van waterbesparing, asook aaneenlopende prosesseringstye wanneer vrugtekosentraat fabrieke teen ‘n volle kapasiteit prosesseer. Daar word ook verslag gedoen oor die effek van verskillende vrug variëteite en vel tipes op die voorkoms van Alicyclobacillus in vrugtekonsentrate. Alicyclobacillus was gemonitor by nege verskillende stadiums van ‘n vrugtekosentraat prosesseringsfabriek tydens die funksionering van óf 'n hersirkulerende óf ‘n deurlopende (nie-hersirkulerende) leigeut waterstelsel. Alicyclobacillus vlakke was beduidend hoër in gemaalde vrugte, enkelsterkte sap, konsentraat en die finale gepasteuriseerde produk (± 30 °Brix), gedurende die funksionering van 'n hersirkulerende leigeutstelsel, in vergelyking met die funksionering van ‘n deurlopende leigeutstelsel (P < 0.05 ). Ongeag van die leigeutstelsel, is hoë vlakke Alicyclobacillus gevind in konsentraat en kondensaat water ('n by-produk van die sap konsentrasie porses) vanuit die verdamper, en maak dit dus ‘n punt van belang tydens die vervaardiging van vrugtekonsentraat. Daar is gevind dat vervaardigingspraktyke soos die hersirkulasie van leigeut water en die herwinnig van kondensaat water moontlike risiko’s inhou vir die besoedeling en akkumulasie van Alicyclobacillus in vrugtekosentrate en die prosesseringsomgewing. Die effek van aaneenlopende prosesseringstye op Alicyclobacillus was gemonitor in 'n vrugtekosentraat prosesseringsfabriek wat teen volle kapasiteit prosesseer. Steekproefneming het elke 12 h by vier prosesseringsstadiums geskied, tydens 'n prosesseringstempo van 1.8 - 2.0 t h-1 vir 108 h. Vegetatiewe selle het beduidend toegeneem (P < 0.05) in die enkelsterkte sap en kondensaat water na 84 uur van prosessering, met 3.15 en 3.85 log10 kve mL-1, onderskeidelik verhaal. Soortgelyke akkumulasiepatrone vir vegetatiewe selle was waargeneem in konsentraat en die finale gepasteuriseerde produk. Endospore in enkelsterkte sap, konsentaat en die finale produk was ook die hoogste na 84 uur van prosessering, met 1.32, 1.59 en 1.64 log10 kve mL-1, onderskeidelik. Wanneer vrugtekonsentraat fabrieke teen volle kapasiteit prosesseseer, kan 'n beperking in aaneenlopende prosesseringstye tot onder 84 h tussen CIP prosedures, gepaard met goeie vervaardigingspraktyke, die akkumulasie van Alicyclobacillus in vrugte konsentate verminder. Die effek van verskillende vrug variëteite se vel tipes, spesifiek harige-vel steenvrugte (perske en appelkoos) en gladde-vel kernvrugte (appel en peer) op die voorkoms van Alicyclobacillus in vrugtekonsentrate was ondersoek. Appel konsentaat monsters het die hoogste voorkoms van vegetatiewe Alicyclobacillus selle gehad (gemiddelde %), met (50%), gevolg deur appelkoos (40%), perske (15%) en peer (10%) konsentraat. Die voorkoms van Alicyclobacillus endospore in vrugte konsentraat monsters was weer die hoogste in appel (50%), gevolg deur peer (25%), appelkoos (20%), en perske (10%) konsentraat. Die voorkoms van Alicyclobacillus vegetatiewe selle en endospore het nie betekenisvol tussen konsentrate van harige-vel en gladdevel vrug variëteite verskil nie (P > 0.05). Die gevolgtrekking was dat vrugte wasstappe, voor die prosessering van vrugtekonsentraat, van meer belang is vir die beheer van Alicyclobacillus as die vel tipe van die vrug variëteit wat geprosesseer word.

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