Quality management and fungal transformation in the edible oil industry
Abstract
English: Approximately 100 000 tonnes of edible frying oil and fat waste, mainly derived from
sunflower oil, is produced each year from the estimated 54 000 frying establishments in
South Africa. Many of these establishments overuse or abuse their oils to save money.
Such practices may result in oil breakdown and the production of harmful compounds,
which can cause diseases such as cancer and diarrhoea when consumed. As a result,
approximately 30 % of frying oil and fat waste in S.A. can be regarded as unhealthy
while the other can be considered still useful for human consumption containing within
S.A. regulatory limits i.e. equal to or less than 16 % polymerised triglycerides (PTGs)
and/or equal to or less than 25 % polar compounds (PCs). In order to ensure that only
oils and fats fit for human consumption are used during frying processes in S.A., it is
important that sound quality control procedures are applied to all sectors of the oil
industry. This is of special significance when taking into consideration the numerous
cases of frying oil misrepresentations, adulteration and overuse reported over the years in
S.A. The approximately 70 % of oil wastes still within the regulatory limits have the
potential to be processed to safe usable foodstuffs such as Evening Primrose Oil
equivalents (EPOeq). Evening Primrose Oil (EPO) has received attention over years as a
medicinal supplement due to its high content of gamma-linolenic acid (GLA). A wellknown
fact is that the positional distribution of GLA on the glycerol moiety of
triacylglycerols has an effect on its functional properties as well as metabolism. When
Mucor circinelloides f. circinelloides CBS 108.16 was cultivated on a mixed substrate of
sunflower oil (30 g/l) containing 1 %, 5 %, 10 %, 15 % and 45 % (w/w) PTGs and
sodium acetate (10 g/l) as carbon sources, most of the oil was utilized after seven days of
growth. Marked increases in biomass production as well as in the lipid content of the
fungal cells were also noted. Strikingly, these sunflower oils were transformed to fungal
oils containing GLA and substantial amounts of linoleic acid (18:2) - also characteristic
of evening primrose oil. This phenomenon was however not observed in the medium
containing only oils with variable amounts of PTGs (40 g/l) and no acetate. In the
presence of acetate, there was an increase in the pH of the medium from pH 5.8 to about
neutrality as well as consumption of PTGs from the growth medium whereas in the
absence of acetate there was a decrease in the medium pH from pH 5.8 to around pH 3.0
while the relative amounts of PTGs kept increasing in the extracellular lipids. The
highest amounts of fungal oils were produced by Mucor circinelloides f. circinelloides
using the 5 % and 10 % (w/w) PTG oils. This study suggests the production of EPOeq
from sunflower oil waste within regulatory limits using Mucor. Stereospecific analysis of
fungal oils obtained from oils with varying PTG concentrations show that the
stereospecific positions of some fatty acids (FAs) vary with different PTG concentrations
whereas certain FAs are found at the same sn position. The 5 % (w/w) PTG oil yielded a
similar FA profile and also a similar sn-distribution profile to that of EPO, however with
increasing PTG concentrations of 10 % (w/w), 15 % (w/w) and 45 % (w/w) the FA
profiles and the sn-distributions were less similar to that of EPO. Gamma-linolenic acid
was found at the sn-2 position in all the oils with varying amounts of PTGs. According
to literature, GLA is found preferentially at the sn-2 and sn-3 positions in EPO. Our
findings with the positional distribution of EPOeq were similar to that of EPO. Both
Nuclear magnetic resonance (NMR) and Gas chromatography (GC) analysis have proved
to be extremely valuable tools in the stereospecific analysis of FAs. Afrikaans: Ongeveer 100 000 ton eetbare kookolie- en vetafval, hoofsaaklik afkomstig vanaf
sonneblomolie, word elke jaar geproduseer deur ongeveer 54 000 braairestaurante in
Suid-Afrika. Baie van hierdie restaurante oorgebruik of misbruik hulle olie om geld te
spaar. Sulke praktyke veroorsaak olie-afbraak en die produksie van skadelik verbindings
wat siektes soos kanker en diaree kan veroorsaak as dit ingeneem word. Dus kan
ongeveer 30 % van kookolie- en vetafval in S.A. beskou word as skadelik terwyl die res
gesien kan word as bruikbaar vir menslike gebruik aangesien dit steeds binne die S.A.
regulatoriese limiete val, d.i. gelyk aan of minder as 16 % gepolimeriseerde trigliseriede
(PTGs) en/of gelyk aan of minder as 25 % polêre komponente (PKs). Om te verseker dat
slegs olies en vette wat geskik is vir menslike gebruik in braaiprosesse in S.A. gebruik
word, is dit belangrik dat goeie kwaliteitsbeheerprosedures in alle afdelings van die olieindustrie
toegepas word. Dit is veral belangrik as die verskeie gevalle van
kookoliewanvoorstelling, -vermenging en oorgebruik wat oor die jare in S.A.
gerapporteer is, inaggeneem word. Die ongeveer 70 % olie-afval wat steeds binne limiete
is, het die potensiaal om na veilige, bruikbare voedingstowwe soos Aandblomolieekwivalente
(AOekw) verwerk te word. Aandblomolie (AO) het oor die jare baie aandag
geniet as ‘n mediese aanvulling as gevolg van ‘n hoë gamma-linoleensuur (GLS) inhoud.
Dis bekend dat die posisionele verspreiding van GLS op die gliseroleenheid van triasielgliserole
‘n effek het op die funksionele eienskappe en metabolisme. Mucor
circinelloides f. circinelloides CBS 108.16 is gekweek in gemengde media met
sonneblomolie (30g/l) wat 1 %, 5 %, 10 %, 15 % of 45 % (m/m) PTGs bevat het, asook
natriumasetaat (10g/l) as koolstofbronne. Meeste van die olie is gebruik na sewe dae van
groei. Merkbare toenames in biomassaproduksie asook lipiedinhoud van fungiselle is
opgemerk. Die sonneblomolies is getransformeer na fungi-olies met GLS en merkbare
hoeveelhede linoleiënsuur (18:2) - ook kenmerkend van AO. Hierdie verskynsel is egter
nie waargeneem in die medium wat slegs olie met verskillende hoeveelhede PTGs (40
g/l) bevat het en geen asetaat nie. In die teenwoordigheid van asetaat, is ‘n toename in
die pH van die medium, vanaf pH 5.8 na ongeveer neutraal, asook ‘n verbruik van PTGs
uit die groeimedium waargeneem. In die afwesigheid van asetaat was daar egter ‘n
afname in die medium se pH, vanaf pH 5.8 na pH 3.0, terwyl die relatiewe hoeveelhede
PTGs in die ekstrasellulêre lipiede toegeneem het. Die grootste hoeveelheid fungi-olie is
geproduseer deur Mucor circinelloides f. circinelloides op 5 % en 10 % (m/m) PTGbevattende
olies. Die studie dui daarop dat die produksie van AOekw vanaf
sonneblomolieafval binne regulatoriese limiete deur Mucor moontlik is. Stereospesifieke
analises van fungi-olie, verkry vanaf olie met verskillende PTG-konsentrasies toon aan
dat die stereospesifieke posisies van sommige vetsure (VSe) variëer met verskilende
PTG-konsentrasies, terwyl ander VSe in dieselfde sn-posisie aangetref word. Die 5 %
(m/m) PTG-olie het ‘n soortgelyke vetsuurprofiel en sn-verspreiding gelewer as AO. Met
toenemende PTG-konsentrasies van 10 % (m/m), 15 % (m/m) en 45 % (m/m) het die
vetsuurprofiele en sn-verspreiding egter minder ooreenstemming getoon met AO.
Gamma-linoleensuur is in die sn-2 posisie gevind in alle olies met verskillende
hoeveelhede PTGs. Volgens literatuur word GLS meestal in die sn-2 en sn-3 posisies in
AO aangetref. Ons bevindinge aangaande die sn-verspreiding van AOekw is soortgelyke
aan die van AO. Beide kernmagnetiese resonansie (KMR) en gaschromatografie (GC)
analises was waardevolle in die stereospesifieke analises.