Efficacy of preservatives on microbial growth and beta carotene retension in ofsp
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Potassium sorbate, sodium benzoate and citric acid together with vacuum packing have extended puree shelf life by 3-6 months in our trials at ambient conditions (T<25C). However, the gap lies on the efficacy of the preservative combination in retarding or stopping the growth of harmful pathogens in the puree, and also their effects on β-carotene retention is unknown.
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Efficacy of preservatives on microbial growth and beta carotene retension in ofsp
- 1. Joyce Ndunge Musyoka MSc. Student (Food Safety and Quality) (University of Nairobi)
- 2. Ø Orange Fleshed Sweetpotato (OFSP) puree is an ingredient in food processing e.g. bakery application Ø Currently processors use freshly made puree or frozen puree because puree is perishable, seasonal and expensive to freeze, store and transport. Ø Proposed solution is development of a shelf-storable OFSP puree which does not require significant refrigeration ( 3-6 months).
- 3. Ø Potassium sorbate, sodium benzoate and citric acid together with vacuum packing have extended puree shelf life by 3-6 months in our trials at ambient conditions (T<25C). Ø However, the gap lies on the efficacy of the preservative combination in retarding or stopping the growth of harmful pathogens in the puree, and also their effects on β-carotene retention is unknown.
- 4. Ø Determine the effect of combination of potassium sorbate, sodium benzoate and citric acid i.e. mild acidification with vacuum package on the keeping quality of OFSP puree. Ø Determine the effect of combination of potassium sorbate, sodium benzoate and citric acid on the growth of the pathogens Staphylococcus aureus and Escherichia coli during storage of OFSP puree. Ø Determine the effect of combination of potassium sorbate, sodium benzoate and citric acid on β-carotene retention in stored OFSP puree.
- 5. Total Viable Counts and Yeast and Molds were analyzed at Time zero, 1 week, 2 weeks, 3 weeks, 5 weeks, 7 weeks and 10 weeks of storage. Room Temperature(T<25oC) Temperature 4oC
- 6. Puree was inoculated with 5.2x109 cfu/ml E.coli and 1.53x109cfu/ml S.aureus and analyzed for these pathogens at 1 week, 2 weeks, 3 weeks, 5 weeks, 7 weeks and 10 weeks of storage. Room Temperature(T<25oC) Temperature 4oC
- 7. Plating puree sample on Coliform agar for E.coli analysis Cfu of E.coli after incubation
- 8. Sample (OFSP) puree FANEL Extraction with methanol,THF - Evaporationunder nitrogenusing N-Evap machine -Reconstitution -Transfer into HPLC vials HPLC analysis (reverse phase gradient HPLC Method -Injectioninto HPLC -PDA detector - C30 carotenoidcolumn (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
- 9. Growth of Total Viable Counts in OFSP puree with preservatives at Room Temperature. Growth of Total Viable Counts in OFSP puree with preservative at Refrigeration Temperature. 0 2 4 6 8 10 0 1 2 3 5 7 10 LogCFU/ml Storage period (Weeks) A B C D E 0 2 4 6 8 10 0 1 2 3 5 7 10 LogCFU/ml Storage period (Weeks) A B C D E The treatments have an effect on destroying bacteria growth in OFSP puree with more effect observed at 4oC compared to room temperature
- 10. Growth of Yeast and Molds in OFSP puree with preservatives at Room Temperature. Growth of Yeast and Molds in OFSP puree with preservative at Refrigeration Temperature. 0 1 2 3 4 5 6 7 8 9 0 1 2 3 5 7 10 LogCFU/ml Storage period (Weeks) A B C D E 0 1 2 3 4 5 6 7 8 9 0 1 2 3 5 7 10 LogCFU/ml Storage period (Weeks) A B C D E The treatments have an effect on destroying Yeast and Molds in stored OFSP puree with more effect observed at 4oC compared to room temperature .
- 12. Ø High initial TVC 1.95x109 cfu/ml is attributed to poor handling of puree during preparation. Ø TVC ,Yeast and Molds were completely inhibited during the storage period. Ø Expansion of packages with citric acid at room temperature and alcoholic odors. Ø Potassium sorbate activity against bacteria but more on yeast and molds. (Saranraj and Geetha, 2012) great effect on molds in baked products.
- 13. Growth of Escherichia coli in OFSP puree with preservatives at Room Temperature. Growth of Escherichia coli in OFSP puree with preservative at Refrigeration Temperature. 0.00 2.00 4.00 6.00 8.00 10.00 12.00 0 1 2 3 5 7 10 LogCFU/ml Storage period (Weeks) A B C D E 0.00 2.00 4.00 6.00 8.00 10.00 12.00 0 1 2 3 5 7 10 LogCFU/ml Storage period (Weeks) A B C D E The treatments have an effect on reducing E.coli growth in stored OFSP puree with more effect observed at 4oC compared to room temperature .
- 14. Growth of Staphylococcus aureus in OFSP puree with preservatives at Room Temperature. Growth of Staphylococcus aureus in OFSP puree with preservative at RefrigerationTemperature. 0.00 2.00 4.00 6.00 8.00 10.00 12.00 0 1 2 3 5 7 10 LogCFU/ml Storage period (Weeks) A B C D E 0.00 2.00 4.00 6.00 8.00 10.00 0 1 2 3 5 7 10 LogCFU/ml Storage period (Weeks) A B C D E Growth of Escherichia coli in OFSP puree with preservative at Refrigeration Temperature. Growth of Staphylococcus aureus in OFSP puree with preservative at Refrigeration Temperature. Growth of Staphylococcus aureus in OFSP puree with preservatives at Room Temperature. The treatments have an effect on reducing S.aureus growth in stored OFSP puree with more effect observed at 4oC compared to room temperature .
- 15. Ø Use of preservatives and citric acid led to significant reduction (p<0.05) in growth of both S.aureus and E.coli by 6 log cycles. Ø Citric acid alone led to significant reduction by 5log cycles. (Seo et al, 2013) - 4 log reduction in chicken meat, 2% citric acid –most effective in reduction of S.aureus under refrigeration. Ø The preservatives were more active against Gram negative bacteria (E.coli).
- 16. 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 at Room Temperature. OFSP puree with preservatives at Refrigeration Temperature. Even with the highest β-carotene loss (47.24%),there is β-carotene content of 5.21mg/100g of puree (RAE 434)-100% requirement for children under 10 years of age and half for adults.
- 17. Ø Sodium benzoate, potassium sorbate and citric acid combinations are able to destroy pathogens and ensure extensive use of puree. Ø Citric acid (pH) alone is not effective in inhibiting the growth of these pathogens. Ø Preservative combinations with 4oC puree storage conditions is more effective in destroying pathogens compared to ambient conditions of storage (T<25oC).
- 18. Ø The preservatives used had an effect in β-carotene retention. Ø High preservative concentrations (>0.2%) in puree should be studied to determine the effect on β-carotene loss.
- 19. Ø CIP for providing the funding for this work and a learning platform through an internship. Ø My supervisors Dr. Abong’ and Dr. Tawanda for the guidance and mentorship, keeping me going when times were tough, asking insightful questions, and offering invaluable advice. Ø Daniel and Derick with Laboratory assistance during the internship. Ø All CIP staff for the warmth and all kinds of support during my stay. I am thankful for being part of this team.