efficacy of preservatives on microbial growth and beta carotene retension in ofsp

Joyce Ndunge MusyokaMSc. Student (Food Safety and Quality)

(University of Nairobi)

Ø Orange Fleshed Sweetpotato (OFSP) puree is aningredient in food processing e.g. bakery application

Ø Currently processors use freshly made puree or frozenpuree because puree is perishable, seasonal andexpensive to freeze, store and transport.

Ø Proposed solution is development of a shelf-storableOFSP puree which does not require significantrefrigeration ( 3-6 months).

Ø Potassium sorbate, sodium benzoate and citric acidtogether with vacuum packing have extended puree shelflife by 3-6 months in our trials at ambient conditions(T<25C).

Ø However, the gap lies on the efficacy of the preservativecombination in retarding or stopping the growth ofharmful pathogens in the puree, and also their effectson β-carotene retention is unknown.

Ø Determine the effect of combination of potassiumsorbate, sodium benzoate and citric acid i.e. mildacidification with vacuum package on the keepingquality of OFSP puree.

Ø Determine the effect of combination of potassiumsorbate, sodium benzoate and citric acid on the growth ofthe pathogens Staphylococcus aureus and Escherichiacoli during storage of OFSP puree.

Ø Determine the effect of combination of potassiumsorbate, sodium benzoate and citric acid on β-caroteneretention in stored OFSP puree.

Total Viable Counts and Yeast and Molds were analyzed at Time zero, 1week, 2 weeks, 3 weeks, 5 weeks, 7 weeks and 10 weeks of storage.

Room Temperature(T<25oC) Temperature 4oC

Puree was inoculated with 5.2x109 cfu/ml E.coli and 1.53x109cfu/mlS.aureus and analyzed for these pathogens at 1 week, 2 weeks, 3weeks, 5 weeks, 7 weeks and 10 weeks of storage.

Room Temperature(T<25oC) Temperature 4oC

Plating puree sample on Coliform agar for E.coli analysis Cfu of E.coli after incubation

Sample (OFSP) puree

FANEL Extraction with methanol, THF- Evaporation under nitrogen using N-Evap machine-Reconstitution-Transfer into HPLC vials

HPLC analysis (reverse phase gradient HPLC Method-Injection into HPLC-PDA detector- C30 carotenoid column (3µm, 150X4.6 mm)-Mobile phase A: methanol/tert-butyl methyl ether/water

(85:12:3, v/v/v, with 1.5% ammonium acetate in the water)-Mobile phase B : methanol/tert-butyl methyl ether/water

(8:90:2, v/v/v, with 1% ammonium acetate in the water).

- Quantification-External standard curve

Growth of Total Viable Counts inOFSP puree with preservatives atRoom Temperature.

Growth of Total Viable Countsin OFSP puree with preservativeat Refrigeration Temperature.

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Storage period (Weeks)A B C D E

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The treatments have an effect on destroying bacteria growth in OFSPpuree with more effect observed at 4oC compared to room temperature

Growth of Yeast and Molds inOFSP puree with preservatives atRoom Temperature.

Growth of Yeast and Molds inOFSP puree with preservative atRefrigeration Temperature.

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Storage period (Weeks)A B C D E

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lStorage period (Weeks)

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The treatments have an effect on destroying Yeast and Molds in storedOFSP puree with more effect observed at 4oC compared to roomtemperature .

Ø High initial TVC 1.95x109 cfu/ml is attributed to poorhandling of puree during preparation.

Ø TVC ,Yeast and Molds were completely inhibited duringthe storage period.

Ø Expansion of packages with citric acid at roomtemperature and alcoholic odors.

Ø Potassium sorbate activity against bacteria but more onyeast and molds. (Saranraj and Geetha, 2012) great effecton molds in baked products.

Growth of Escherichia coli inOFSP puree with preservatives atRoom Temperature.

Growth of Escherichia coli inOFSP puree with preservative atRefrigeration Temperature.

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The treatments have an effect on reducing E.coli growth in storedOFSP puree with more effect observed at 4oC compared to roomtemperature .

Growth of Staphylococcusaureus in OFSP puree withpreservatives at RoomTemperature.

Growth of Staphylococcus aureus inOFSP puree with preservative atRefrigeration Temperature.

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Growth of Escherichia coli inOFSP puree with preservative atRefrigeration Temperature.

Growth of Staphylococcus aureus inOFSP puree with preservative atRefrigeration Temperature.

Growth of Staphylococcus aureus inOFSP puree with preservatives atRoom Temperature.

The treatments have an effect on reducing S.aureus growth in storedOFSP puree with more effect observed at 4oC compared to roomtemperature .

Ø Use of preservatives and citric acid led to significantreduction (p<0.05) in growth of both S.aureus and E.coliby 6 log cycles.

Ø Citric acid alone led to significant reduction by 5logcycles. (Seo et al, 2013) - 4 log reduction in chickenmeat, 2% citric acid –most effective in reduction ofS.aureus under refrigeration.

Ø The preservatives were more active against Gramnegative bacteria (E.coli).

Baseline β-carotene (g/100g)

End line(mg/100g)

% β-carotene loss

9.88 5.55 43.83

9.88 5.58 43.52

9.88 5.21 47.24

9.88 6.66 32.59

9.88 6.09 38.36

Baseline β-carotene

(mg/100g)

End line (mg/100g)

% β-carotene loss

9.88 6.24 36.84

9.88 5.37 45.65

9.88 6.58 33.4

9.88 6.11 38.16

9.88 6.7 32.19

OFSP puree with preservatives atRoom Temperature.

OFSP puree with preservativesat Refrigeration Temperature.

Even with the highest β-carotene loss (47.24%),there is β-carotenecontent of 5.21mg/100g of puree (RAE 434)-100% requirement forchildren under 10 years of age and half for adults.

Ø Sodium benzoate, potassium sorbate and citric acidcombinations are able to destroy pathogens and ensureextensive use of puree.

Ø Citric acid (pH) alone is not effective in inhibiting thegrowth of these pathogens.

Ø Preservative combinations with 4oC puree storageconditions is more effective in destroying pathogenscompared to ambient conditions of storage (T<25oC).

Ø The preservatives used had an effect in β-caroteneretention.

Ø High preservative concentrations (>0.2%) in pureeshould be studied to determine the effect on β-caroteneloss.

Ø CIP for providing the funding for this work and alearning platform through an internship.

Ø My supervisors Dr. Abong’ and Dr. Tawanda for theguidance and mentorship, keeping me going whentimes were tough, asking insightful questions, andoffering invaluable advice.

Ø Daniel and Derick with Laboratory assistance during theinternship.

Ø All CIP staff for the warmth and all kinds of supportduring my stay. I am thankful for being part of this team.