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.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/6610 |
| Date | 03 1900 |
| Creators | Steyn, Catharina Elizabeth |
| Contributors | Witthuhn, R. C., Cameron, M., University of Stellenbosch. Faculty of AgriSciences. Dept. of Food Science. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | 88 p. |
| Rights | University of Stellenbosch |
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