Masters Degrees (Food Science)

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Browsing Masters Degrees (Food Science) by browse.metadata.advisor "Caleb, Oluwafemi James"

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    Effects of packaging and storage condition on functional properties and quality attributes of cassava flour (CVS. ‘TME 419’ AND ‘UMUCASS 36’)
    (Stellenbosch : Stellenbosch University, 2015., 2015-04) Uchechukwu-Agua, Amarachi Divine; Opara, Umezuruike Linus; Manley, Marena; Caleb, Oluwafemi James; Stellenbosch University. Faculty of Agrisciences. Dept. of Food Science.
    ENGLISH ABSTRACT: Cassava flour is recommended for substitution with wheat flour in composite flour for baking. The potential use of cassava flour in the food and pharmaceutical industries is attributed to its gluten-free nature and excellent functional properties. However, optimum packaging solution and storage conditions for cassava flour is critical in maintaining the quality attributes and shelf-life stability during storage. Therefore, this study focused on investigating the effects of package types (plastic buckets, low density polyethylene (LDPE) bags and brown paper bags) and storage conditions (cool condition (15 °C, 90% RH); ambient condition (23 °C, 60% RH); and higher condition (38 °C, 60% RH)) on the functional properties, quality attributes and shelf-life stability of cassava flour (cvs. ‘TME 419’ and ‘UMUCASS 36’) developed at the National Root Crops Research Institute, Umudike, Nigeria. Proximate composition, physicochemical attributes, functional properties, and microbial safety of flour were analysed every 4 weeks for 12 weeks storage duration. Flour stored under cool condition with paper bags became moist and sticky with appearance of mould growth before 4 weeks of storage. However, at the end of 12 weeks storage, a decline in moisture content of 11.00 ± 0.02 and 7.05 ± 0.01% flour of ‘TME 419’ was observed at ambient and higher conditions, respectively. Rate of moisture decline was similar in flour of ‘UMUCASS 36’. A slight decrease in protein content of flour was observed during the 12 weeks storage from 1.9 ± 0.07 to 1.30 ± 0.001% for cv. ‘TME 419’ and 3.0 ± 0.05 to 2.27 ± 0.001% for cv. ‘UMUCASS 36’; however, no significant difference was observed under ambient and higher conditions. Cassava flour packed in paper bags and stored under higher condition (38 °C, 60%) had the highest loss (50%) of carotenoid content from 1.84 ± 0.10% to 0.91 ± 0.08%, while a minimal loss (24%) of carotenoid was observed in flour packed in plastic buckets under ambient condition. The concentration of hydrogen cyanide (HCN) decreased across all treatments and was below the safe cyanide level of 50 µg/ mL for food products. After the 12 weeks of storage, flour packed in plastic buckets had the highest aerobic mesophilic bacterial counts (3.43 ± 0.04 log cfu/ g) followed by flour in LDPE bags (3.37 ± 0.03 log cfu/ g) and paper bags (3.35 ± 0.01 log cfu/ g). No significant difference was observed in the package types; however the counts observed were within the acceptable microbial limit Swelling power (SP), solubility and peak viscosity were used to characterise the changes in functional and pasting properties of cassava flour relevant in food industries. Flour packed in plastic buckets under ambient condition had the lowest swelling power (8.48 ± 0.55%) and peak viscosity (260 ± 0.51 RVU) compared to flour packed in LDPE and paper bags with (9.10 ± 0.13 and 9.32 ± 0.41%) SP and (263.67 ± 4.04 RVU and 302 ± 9.52 RVU) peak viscosity, respectively. The essential minerals (sodium, potassium, copper, and iron) were significantly higher in flour of ‘TME 419’ compared to ‘UMUCASS 36’. In summary, for the production of high grade foods such as bread where higher swelling power and viscosities are required, flour from ‘TME 419’ packed with paper bags under higher condition could be desirable. In addition, for infant formulation, flour from ‘UMUCASS 36’ packed in plastic buckets and stored under ambient condition which best maintained nutritional contents (protein and fat) and had the lowest peak viscosity would be more suitable. Flour from both cassava cultivars could be stored up to 12 weeks duration under ambient and hot tropical conditions using all package types evaluated. However, storage with paper bag under higher condition offers the chances of better shelf -life stability of cassava flour.
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    Modified atmosphere packaging and quality of fresh Cape hake (Merluccius capensis) fish fillets
    (Stellenbosch : Stellenbosch University, 2014-12) Oluwole, Adebanji Olasupo; Opara, U. L.; Manley, M.; Caleb, Oluwafemi James; Stellenbosch University. Faculty of AgriSicences. Dept. of Food Science.
    ENGLISH ABSTRACT: Fresh ready-to-cook fish fillets are prone to rapid loss of freshness and other quality attributes, as well as accelerated growth of spoilage micro-organisms under sub-optimal storage conditions. Cape hake (Merluccius capensis) is an important seafood in South Africa; however, rapid loss of quality and eventual spoilage is a problem limiting the economic potential. Thus, the aim of this study was to investigate the effects of active (40% CO2 + 30% O2 + 30% N2) and passive (0.039% CO2 + 20.95% O2 + 78% N2) modified atmosphere packaging (MAP) under different storage temperatures (0°C, 4°C, and 8°C) on the quality attributes of Cape hake (Merluccius capensis) fish fillets. This was achieved by investigating the effects of MAP (with or without absorbent pads) and storage temperature on quality attributes (microbial, physicochemical and sensory), changes in composition and concentration of volatile compounds (VOCs) and shelf life of Cape hake fillets. Modified atmosphere packaging, storage temperature and the use of absorbent pads had a significant (p < 0.05) impacts on physicochemical properties of Cape hake fillets during refrigerated storage. Highest storage temperature (8°C) led to accelerated deterioration of packaged Cape hake fillets. Generally, active MAP better maintained the quality attributes of Cape hake than passive MAP at 0°C and 4°C. Headspace gas composition of O2 and CO2 were significantly influenced by the storage time, temperature, MAP conditions and their interactions (p < 0.05). Irrespective of storage temperature, active-MA packaged fillets had lower pH values in comparison to fillets stored under passive-MAP. Drip loss was higher in active-MA fillets packaged without absorbent pad. Passive-MAP fillets did not show any drip loss. Absorbent pad was used to add value to MAP storage as MAP resulted in drip. The use of absorbent pad combined with low storage temperature maintained the firmness of hake fillets, across all temperatures. The interaction of MAP, absorbent pad and storage temperature had a significant effect on the aerobic mesophillic bacteria counts. Based on the aerobic mesophillic bacteria count fillets stored under active-MAP at 0°C (5.2 log cfu/g) was limited to day 12, while the fillet stored under passive-MAP at 0°C (log cfu/g) was limited to greater than day 3. Overall sensory acceptability of fillets decreased with increase in storage temperature across all treatments. Additionally, MAP had a significant (p < 0.05) impact on sensory attributes such as appearance and odour acceptability, with active-MA packaged fillets stored at 0°C having highest overall acceptability. A total of 16 volatiles were identified in Cape hake fillets, including 4 primary VOCs and 12 secondary VOCs. The VOCs associated with spoilage include tri-methylamine (TMA) (ammonia like), esters (sickeningly sweet) and sulphur group (putrid). MAP had a significant (p< 0.05) influence on volatile composition and concentration. Active-MA packaged fillets performed better during storage and had lower TMA value of 0.85% on day 12 in comparison with 7.22% under passive-MAP on day 6 at 0°C. The results obtained demonstrated that changes in volatile compounds were significantly (p< 0.05) influenced by storage duration, temperature and MAP. The development of high levels of VOCs and off-odour corresponded with high aerobic mesophillic bacteria count (≥ 5.5 log cfu/g). Based on these developments the storage life of Cape hake fillets packaged under active-MAP with absorbent pad and stored at 0°C was limited to 12 d, while the passive-MAP (control) fillets stored at 0°C was limited to 3 d. The use of active-MAP, in combination with absorbent pads and 0°C storage in addition to good hygienic practices, was effective in maintaining the postharvest quality of Cape hake fish fillets and led to higher shelf life.
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    Perforation-mediated modified atmosphere packaging (PM-MAP) and shelf-life of pomegranate fruit arils (cv. ACCO)
    (Stellenbosch : Stellenbosch University, 2014-12) Hussein, Zaharan; Opara, Umezuruike Linus; Marena, Manley; Caleb, Oluwafemi James; Stellenbosch University. Faculty of AgriSciences. Dept. of Food Science.
    ENGLISH ABSTRACT: Perforation-mediated modified atmosphere packaging (PM-MAP) offers the possibility of optimising polymeric films in order to compensate for barrier limitations of conventional modified atmosphere packaging (MAP). The aim of this study was to investigate the effects of PM-MAP and storage duration on the physico-chemical quality attributes, microbial quality, phytochemicals (anthocyanins, phenolics and ascorbic acid) and antioxidant activities of arils from fresh minimally processed pomegranate (cv. Acco). The effects of number of perforations (0, 3, 6 and 9; Ø = 0.8 mm) and storage temperature (5, 10 and 15 ºC) on water vapour transmission rate (WVTR, g/m2.day) of synthetic ‘Polylid’ and biodegradable (Nature flexTM) polymeric films were investigated. The results showed that non-perforated biodegradable film had higher WVTR at all storage temperatures, and irrespective of film type, increasing the number of perforations (from P-3 to P-9) had higher impact on WVTR than increasing storage temperature (from 5 to 15 ºC). Furthermore, this study investigated the effects of PM-MAP on the physico-chemical properties, phytochemicals components and antioxidant activities of fresh minimally processed arils. Arils (100 g) were packaged in polypropylene trays (10.6 x 15.1 cm2) and heat-sealed with a polymeric film POLYLID®. Perforations (0, 3, 6 and 9; Ø = 0.8 mm) were made on the top of the film and all samples were stored at 5 ± 1 ºC and 95 ± 2% relative humidity for 14 days. Samples were analysed at intervals of 3, 6, 9, 12 and 15 days. Microbial analysis included tests for Escherichia coli, aerobic mesophilic bacteria, yeast and moulds at days 0, 6, 10 and 14. The results showed that headspace gas composition was significantly influenced by the number of perforations, which helped balance the decrease in O2 with corresponding increase in CO2 levels, thus preventing anoxic conditions. Total soluble solids, titratable acidity and firmness of arils were slightly reduced by PM-MAP compared to clamshell trays. Colour attributes was generally maintained across all treatments and throughout the storage duration. The highest counts of aerobic mesophilic bacteria (5.5 log CFU/g), yeast and moulds (5.3 log CFU/g) were observed in P-0 and P-9 packages, respectively. Overall, P-3 and P-6 better maintained the physico-chemical properties and microbial quality of arils. Total phenolics and anthocyanin contents were higher in arils packaged in PM-MAP while ascorbic acid was slightly reduced. Antioxidant activities tested against FRAP and DPPH radical-scavenging activity increased across all types of MAP over storage duration. However, antioxidant activities were significantly higher in pomegranate arils packaged in PM-MAP due to O2-promoted biosynthesis of phenolics and anthocyanins which constitute the antioxidant properties. Overall, the results reported in this study showed that the use of PM-MAP in cold chain could be suitable for the preservation of physico-chemical quality, phytochemical contents and antioxidant properties of arils packaged in passive PM-MAP compared to clamshell and non-perforated packages during postharvest handling and storage. Perforating MAP films showed potential in preventing the incidence of in-package moisture condensation which is a common problem during postharvest handling and storage of fresh produce packaged inside non-perforated MAP. The results also showed the importance of keeping PM-MAP packs in closed refrigerated shelves to avoid cross contamination or ingress of foodborne pathogens.
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    Postharvest physiology and effects of modified atmosphere packaging and anti-browning treatment on quality of pomegranate arils and aril-sac (CV. Bhagwa)
    (Stellenbosch : Stellenbosch University, 2014-04) Aindongo, Wilhelmina Vulikeni; Opara, Umezuruike Linus; Manley, Marena; Caleb, Oluwafemi James; Stellenbosch University. Faculty of AgriSciences. Dept. of Food Science.
    ENGLISH ABSTRACT: Knowledge of postharvest quality attributes of minimally processed packaged fruit is essential in order to establish the optimum shelf life period. The aim of this study was to investigate the effects of Passive-modified atmosphere packaging (MAP) on the quality of minimally processed pomegranate (cv. Bhagwa) arils and aril-sacs. These began by understanding the physiological processes i.e. respiration and transpiration rates of the whole fruit, arils and aril-sacs. The respiration rates (RR) of whole fruit, aril-sacs and arils were studied at 5, 10, 15 and 22°C, and comparisons were made among these fruit fractions. A high RR was observed in aril-sacs compared to whole fruit and arils across all storage temperatures. A 74.5% decrease in RR was observed when storage temperature was reduced from 22°C to 5°C. A significant increase in RR occurred from day 3 of storage across all fruit fractions and storage temperatures. The transpiration rates (TR) of arils and aril-sacs were studied at storage conditions of 5, 10 and 15°C and 76, 86 and 96% relative humidity (RH), and was found to increase with increase in temperature and decrease in relative humidity, with lowest TR occurring in fruit fractions stored at 5°C and 96% RH showing lower TR. Arils had high TR compared to aril-sacs, and this may be related to high surface area to volume ratio of exposed arils. The effects of modified atmosphere packaging and application of anti-browning agents on quality of arils and aril-sacs stored at 5°C were studied. Compared to clamshell packaging, Passive-MAP using POLYLID® 107 polyethylene (PE) polymeric film showed greater positive effects in maintaining the quality and extends the shelf life of the arils and aril-sacs. Furthermore, the anti-browning agents used controlled browning on the cut-surfaces of the peel of the aril-sacs and reduced microbial growth in both arils and aril-sacs. When the effects of MAP and anti-browning were combined, aril-sacs stored better than arils. These treatments extended the shelf life of aril-sacs to 12 days while arils lasted up to 9 days. The water vapour transmission rate (WVTR) of pomegranate fruit membrane was evaluated at cold storage (5°C, 90% RH) and room condition (18.7°C, 70% RH). A high WVTR occurred in membranes stored at room condition, compared to those stored at cold storage. Further studies are warranted to improve our understanding of the biophysical properties of pomegranate membranes in relation to possible exchange of water vapour and gases between the aril-sacs. In summary, the use of MAP in combination with anti-browning agents showed a high potential in maintaining the quality of pomegranate arils and aril-sacs and consequently increase their shelf-life.