Browsing by Author "Chaula, Davis"
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Item Changes in fatty acids during storage of artisanal-processed freshwater sardines (Rastrineobola argentea)(WILEY, 2023) Chaula, Davis; Jacobsen, Charlotte; Laswai, Henry S.; Chove, Bernard Elias; Dalsgaard, Anders; Mdegela, Robinson; Hyldig, GretheFor ages, indigenous small fish species have been important in food and nutritional security of poor communities in low income countries. Freshwater fish, in particu- lar fatty fish species are attracting a great attention because they are good sources of health promoting long chain omega-3 fatty acids. Docosahexaenoic acid (DHA, C22:6n-3), Docosapentaenoic acid (DPA, C22:5n-3) and eicosapentaenoic acid (EPA, C20:5n-3) are the main omega-3 PUFAs known to confer health benefits in humans if consumed in required amounts. While nutritionally valued, omega-3 PUFAs in fish are susceptible to oxidative damage during processing, transportation and subsequent storage. Lake Victoria sardines (Rastrineobola argentea), are rich source of chemically unstable omega-3 fatty acids DHA, DPA and EPA. Traditionally, sardines are pre- served by sun drying, deep frying and smoking. Sardine products are transported, stored and marketed at ambient temperatures. Generally, uncontrolled and higher temperatures are known to increase vulnerability of polyunsaturated fatty acids to oxidation which in turn results into loss of nutritional and sensory qualities. This study investigated changes of fat acids in sun dried, deep fried and smoked sardines during storage. Lipolysis and the progressive hydroperoxides formation were monitored by free fatty acids (FFAs) and peroxide value (PV) respectively. None volatile secondary products of lipid oxidation were measured by thiobabituric acid reactive substances (TBARS). Fatty acids were analyzed by gas chromatography with a flameionization de- tector (GC-FID). Deep fried sardines maintained the lowest and apparently stable PV, TBARS and FFAs. Proportions of saturated fatty acids and polyunsaturated fatty acids decreased with time while that of monounsaturated fatty acids increased. Omega-3 fatty acids EPA, DPA and DHA decreased with increase in storage time. In 21 days of storage, DHA was oxidized beyond detectable levels in all sardine products. Gradual increase in FFAs in sun dried sardines was suggestive of lipid hydrolysis induced by enzymes.Item Effect of clove (Syzygium aromaticum) and seaweed (Kappaphycus alvarezii) water extracts pretreatment on lipid oxidation in sun‐dried sardines (Rastrineobola argentea) from Lake Victoria, Tanzania(Food Science & Nutrition published by Wiley Periodicals, Inc., 2019) Chaula, Davis; Laswai, Henry; Chove, Bernard; Dalsgaard, Anders; Mdegela, Robinson; Jacobsen, Charlotte; Hyldig, GretheSmall indigenous fish species play a significant role in food and nutritional security of poor communities in developing countries. Sardines (Rastrineobola argentea) are fish species of Lake Victoria known to be a good source of health‐promoting omega‐3 fatty acids. Open sun drying is a common and traditional sardine processing and preservation method. Sun‐dried products suffer from characteristic off‐flavor due to lipid oxidation which discourage product consumption and limit diversification. This study investigated the use of clove (Syzygium aromaticum) and seaweed (Kappaphycus alvarezii) water extracts as natural antioxidants to impede lipid oxidation in sun‐dried sardines. Lipid oxidation was assessed by peroxide value, volatile secondary oxida- tion products, and fatty acid profiles. The antioxidant capacity of extracts was evalu- ated by total phenolic content, 1, 1‐diphenyl‐2‐picrylhydrazyl (DPPH) radical scavenging, and iron (Fe 2+ ) chelating ability. Results showed that 5, 10, and 20 g/L clove extracts significantly reduced peroxidation in sun‐dried sardines by 38.7%, 54.6%, and 56%, respectively. Clove extracts resulted in higher retention of omega‐3 fatty acids and lower concentrations of secondary lipid oxidation products as op- posed to seaweed counterpart. This research has demonstrated feasibility of pre- treating whole, omega‐3‐rich small sardines with natural antioxidants to avert lipid oxidation during sun drying.Item Effect of final moisture content, cooling time and paddy variety on milling quality of rice (Oryza sativa, L.)(Pearl Research Journals, 2016) Furahisha, Kulwa; Chove, Lucy Mlipano; Chaula, DavisThe study was carried out to establish the effects of three factors -final moisture content (FMC), shade-cooling time (CT) and paddy variety on rice milling quality. Paddy was sun dried to final moisture contents ranging from 9.0 to 15.5% (on wet basis) and shade-cooled for 0, 6, 12, 18, and 24 h at ambient temperature (27.20 to 35.10 o C). Five paddy varieties, TXD 88, TXD 306, SUPA, IRRITA 1, and IRRITA 2 were studied. The milling tests were carried out using a laboratory rice mill. Latin square design with 5 replications (5x5 orders) was used. Physical properties and milling quality in terms of total rice yield (TRY), head rice yield (HRY) and whiteness index (WI) were analyzed. The physical properties differed significantly (P<0.05) among varieties. SUPA had good size, shape and chalkiness whereas TXD 88 had poor quality for all these parameters. IRRITA 1 and IRRITA 2 produced higher TRY compared to other tested varieties. TXD 88 had higher whiteness index but lower HRY compared to other tested varieties. Higher yields, which were significantly different for TRY and HRY (P<0.05) were obtained at moisture content between 9.0 to 12.5% for TRY, but between 10.5 to 14.0% for HRYItem Fatty acid profiles and lipid oxidation status of sun dried, deep fried, and smoked sardine (Rastrineobola argentea) from Lake Victoria, Tanzania(Taylor & Francis, 2019) Chaula, Davis; Laswai, Henry; Chove, Bernard; Dalsgaard, Anders; Mdegela, Robinson; Hyldig, GretheFreshwater fishes contain long chain omega-3 and omega-6 polyunsaturated fatty acids (PUFAs) of highest nutritional value. PUFAs in fish are susceptible to oxidative damage during processing and subsequent storage. Sardines (Rastrineobola argentea) are an important fish species of Lake Victoria, constitut- ing 72.3% of the total landings by weight on the Tanzanian side of the lake. Fatty acid profiles and lipid oxidation status of sun-dried, deep-fried, and smoked sardines were investigated. Lipid oxidation was assessed by peroxide value, thiobarbituric acid reactive substances (TBARS), and free fatty acids. Fatty acids were analyzed by gas chromatography with flame ionization detector. The three omega-3 PUFAs: docosahexaenoic acid (C22:6n-3), docosapentaenoic acid (C22:5n-3), and eicosapentaenoic acid (C20: 5n-3) contributed 57–60, 63, and 38% of PUFAs in sun-dried, smoked, and deep-fried sardines, respectively. Lipid oxidation reactions were more pronounced in sardines dried on sand and rocks, with TBARS values 97.87 and 84.18 μmolMDA/kg, respectively. The polyene index was significantly lower (p < 0.05) in deep-fried sardines, indicating lower retention of PUFAs in the product. Lake Victoria sardines are a rich source of omega-3 PUFAs. PUFAs in sun-dried sardines are prone to oxidative damage. Smoking resulted in relatively higher retention of omega-3 fatty acids in products.Item In situ pectin engineering as a tool to tailor the consistency and syneresis of carrot purée(Elsevier, 2012) Christiaens, Stefanie; Buggenhout, Sandy Van; Chaula, Davis; Moelants, Katlijn; David, Charlotte C.; Hofkens, Johan; Loey, Ann M. Van; Hendrickx, Marc E.To investigate whether in situ pectin engineering would be a helpful tool in tailoring the consistency and syneresis of vegetable purées, carrot was selected as a plant tissue in which the textural properties are largely influenced by pectin methylesterase-induced pectin changes. The effect of low-temperature and high-temperature blanching, as well as the effect of two types of mechanical disruption, blending and high-pressure homogenisation, on the flow properties of carrot purée was explored. The influence of these different purée preparation steps on pectin was examined via physicochemical analysis of fractionated walls and isolated polymers, and via anti-pectin antibodies entailing in situ and ex situ analyses. Purée prepared by blending non-pretreated carrots showed a rather high consistency and pronounced syneresis. Treatments that solubilise pectin, such as high-pressure homogenisation and, in particular, high-temperature blanching, limited syneresis phenomena. In contrast, when the intercellular adhesion in carrot tissue was strengthened via low-temperature blanching, the degree of syneresis increased. High-pressure homogenisation was useful to reduce the carrot tissue particle size and, consequently, resulted in a lower consistency carrot purée. Low-temperature blanching on the other hand increased the consistency of carrot purée as the higher level of intercellular adhesion presumably led to an increased resistance to particle disintegration upon blending or high-pressure homogenisationItem Natural antioxidants from clove for protecting omega-3 fatty acids in sardines (Rastrineobola argentea) during deep frying process.(Sokoine University of Agriculture, 2019-04-11) Chaula, Davis; Jacobsen, Charlotte; Laswai, Henry; Chove, Bernard; Dalsgaard, Anders; Mdegela, Robinson; Hyldig, GretheSardines (Rastrineobola argentea), popularly known as “dagaa” is one of the leading commercial fish species of Lake Victoria. The fatty fish species are attracting great attention because they are good source of omega-3 polyunsaturated fatty acids which are vital for a wide range of biological functions and are implicated in the prevention of numerous diseases. While nutritionally valued omega-3 fatty acids are highly susceptible to oxidation during fish processing due to their unsaturated nature. Oxidation reactions result in loss of omega-3 fatty acids and production of undesired off-flavours which discourage consumption and limit diversification of sardine products.Synthetic antioxidants may be used to prevent lipid oxidation but have been claimed to be carcinogenic at higher levels. The replacement of synthetic antioxidants with ones of natural origin is now in demand. In this study, natural antioxidants rich extracts from clove buds were applied on sardines in a bid to impede lipid oxidation during deep frying process. Lipid oxidation was assessed by peroxide value (PV), volatile compounds and fatty acid profiles using Gas chromatograph (GC-MS and GC-FID).The results showed that natural antioxidants from clove buds reduced peroxidation and protected highly unsaturated omega-3 fatty acids from oxidation during deep frying process. Total polyunsaturated fatty acids amounted 7.30 % in pre-treated deep fried sardines.Retention of omega-3 fatty acids was 0.70 % more in pre-treated than untreated fish. Significantly lower amounts of representative volatile compounds were produced in sardines pre-treated with clove extracts. The study demonstrated feasibility to pre-treat sardines with natural antioxidants for protecting omega-3 fatty acids against oxidation during deep frying.Item Protection against oxidation of Omega-3 Fatty Acids with natural antioxidants in clove (szygium aromaticum) water extracts during storage of sun dried sardines (Ratrineobola Argentea)(Fortune Journals, 2019) Chaula, Davis; Jacobsen, Charlotte; Laswai, Henry; Chove, Bernard; Dalsgaard, Anders; Mdegela, Robinson; Hyldig, GretheOmega-3 fatty acids are a family of polyunsaturated fatty acids (PUFAs) with beneficial health effects to humans if consumed in required amounts. Fatty fish species are known to be rich in marine-based omega-3 fatty acids, eicosapentaenoic acid (EPA, 20:5n-3), docosahexaenoic acid (DHA, C22:6n-3) and docosapentaenoic acid (DPA, C22:5n-3). Sardines (Rastrineobola argentea) from Lake Victoria are a good source of health promoting omega-3 fatty acids. Open sun drying is a common and traditional sardine processing and preservation method. Due to their chemical instability omega-3 fatty acids in sun dried sardines are prone to lipid oxidation during processing and subsequent storage. This study investigated the use of clove (Syzygium aromaticum) water extracts as natural antioxidants to protect omega-3 fatty acids against oxidative damage during storage of sun dried sardines. Lipid oxidation was assessed by peroxide value, volatile secondary oxidation products and fatty acid profiles. The antioxidant capacity of extracts was evaluated by total phenolic content, 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging and iron (Fe 2+ ) chelating ability. Clove extracts resulted into significantly higher retention of total PUFAs, DHA, EPA and DPA at the end of 30 days storage period and lower concentrations of secondary lipid oxidation products. This is an evidence of their enhanced oxidative stability in the real food system due to presence of natural clove antioxidants.Item Unravelling process-induced pectin changes in the tomato cell wall: An integrated approach(Elsevier ltd., 2011) Christiaens, Stefanie; Buggenhout, Sandy Van; Houben, Ken; Chaula, Davis; Loey, Ann M. Van; Hendrickx, Marc E.The activity of the pectin-modifying enzymes pectin-methylesterase (PME) and polygalacturonase (PG) in tomato fruit was tailored by processing. Tomatoes were either not pretreated, high-temperature blanched (inactivation of both PME and PG), or high-pressure pretreated (selective inactivation of PG). Subsequently, two types of mechanical disruption, blending or high-pressure homogenisation, were applied to create tomato tissue particle suspensions with varying degrees of tissue disintegration. Pro- cess-induced pectin changes and their role in cell–cell adhesion were investigated through in situ pectin visualisation using anti-pectin antibodies. Microscopic results were supported with a (limited) physico- chemical analysis of fractionated walls and isolated polymers. It was revealed that in intact tomato fruit pectin de-esterification is endogenously regulated by physical restriction of PME activity in the cell wall matrix. In disintegrated tomato tissue on the other hand, intensive de-esterification of pectin by the activity of PME occurred throughout the entire cell wall. PG was selectively inactivated (i.e. in high- pressure pretreated tomatoes), with de-esterification of pectin by PME, which resulted in a high level of Ca 2+ -cross-linked pectin and a strong intercellular adhesion. In non-pretreated tomato suspensions on the other hand, combined PME and PG activity presumably led to pectin depolymerisation and, hence, reduced intercellular adhesion. However, because of the high amount of Ca 2+ -cross-linked pectin in these samples, cell–cell adhesion was still stronger than in the high-temperature blanched tomatoes, in which the absence of PME activity during suspension preparation implied few Ca 2+ -cross-linked pectic polymers and extensive cell separation upon tissue disruption.