Browsing by Author "Ohene Afoakwa, E."
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Item Acidification and starch behaviour during co-fermentation of cassava (Manihot esculenta Crantz) and soybean (Glycine max Merr) into gari, an African fermented food(2010) Ohene Afoakwa, E.; Kongor, J.E.; Amponsah, G.; Adjonu, R.Changes in acidification and starch behaviour were investigated during co-fermentation of cassava and soybean into gari, an African fermented product. Non-volatile acidity, pH and starch content were evaluated using standard analytical methods. Starch breakdown and pasting characteristics were also analysed using a Brabender viscoamylograph. Fermentation caused significant variations in the pH, non-volatile acidity and starch concentration. The pH decreased with concomitant increases in non-volatile acidity during co-fermentation of the cassava dough. Soy fortification up to 20% caused only minimal effects on the pH, titratable acidity and starch content during the fermentation period. Starch content decreased from 69.8% to 60.4% within the 48 h fermentation time in the unfortified sample, with similar trends noted at all levels of fortification. Starch pasting characteristics showed varied trends in pasting temperature, peak viscosity, viscosity at 95_C and at 50_C-hold with increasing fermentation time and soybean concentration. Cassava could be co-fermented with soybean up to 20% concentration during gari processing without significant effect on its process and product quality characteristics.Item Application of response surface methodology for studying the quality characteristics of cowpea-fortified nixtamalized maize(Innovative Food Science and Emerging Technologies, 2003-03) Sefa-Dedeh, S.; Cornelius, B.; Sakyi-Dawson, E.; Ohene Afoakwa, E.Studies were conducted on the chemical and functional properties of fermented cowpea-fortified nixtamalized maize using response surface methodology. The central composite rotatable design for K = 3 was used to study the combined effect of lime concentration (0-1%), moisture content (55-65%) and cowpea level (0-30%) on pH, titratable acidity, water absorption, protein and viscosity of fermented nixtamalized maize. Regression models were developed to predict the variables. The presence of lime and cowpea influenced the pH, titratable acidity, water absorption, protein content and the cooked paste viscosity of the fermented cowpea-fortified maize. The presence of lime during fermentation generally decreased titratable acidity, water absorption and cooked paste viscosity while the addition of cowpea increased most of the studied indices. Cowpea fortification can therefore be used to increase the nutritive value of nixtamalized maize with acceptable product quality characteristics. © 2002 Elsevier Science Ltd. All rights reserved.Item Canning Technology – Principles, Applications and Recent Technological Advances.(Nova Science Publishers, Inc. (2007), 2007) Ohene Afoakwa, E.Item Characterization of melting properties in dark chocolates from varying particle size distribution and composition using differential scanning calorimetry.(2007) Ohene Afoakwa, E.; Alistair, P.; Fowler, M.; Vieira, J.Melting properties in dark chocolates processed from varying particle size distribution (PSD), fat and lecithin content were studied using differential scanning calorimetry (DSC). Compositional parameters were PSD (D90 (90% finer than this size) of 18, 25, 35 and 50 μm), fat (25%, 30% and 35%) and lecithin (0.3% and 0.5%) contents. Variations in PSD had no influence on crystallinity of products. Fat and lecithin content influenced the degree of crystallinity and melting properties (Tend, Tindex and DHmelt) of the products. Increasing fat content caused consistent increases in degree of crystallinity and crystal size distribution, thus effecting significant changes in Tend, Tindex and DHmelt of their derived products. Increasing lecithin content however reduced the crystal sizes in products. Particle size (PS) increases had limited effects on Tonset, Tpeak, and DHmelt independent of fat and lecithin content. Significant decreases in Tend and Tindex were noted with PS increases at all fat and lecithin contents. Similar increases in Tend and Tindex were noted with increases in fat content at all PS and lecithin levels. Contrary, increasing lecithin content in products resulted in significant decreases in Tend, Tindex and DHmelt. Thus, variations in fat and lecithin contents during dark chocolate manufacture influence the crystallinity of products, and with PSD, they all influence the melting index (duration) of their derived productsItem Chocolate Science and Technology(Wiley-Blackwell Publishers Inc. (2010). (Hardcover)., 2010) Ohene Afoakwa, E.Item Cocoa and chocolate consumption – Are there aphrodisiac and other benefits for human health?(2008) Ohene Afoakwa, E.Cocoa and chocolate have been acclaimed for several years for their possible medicinal and health benefits. It is only recently, however, that some of these claims have been more clearly identified and studied. Recent epidemiological and clinical studies, for example, have shown that dietary supplementation with flavonoid-rich cocoa and chocolate may exert a protective effect on low-density lipoprotein (LDL) oxidation, which has been associated with a reduced risk of developing atherosclerosis. Some of the identified benefits of flavonoid-rich cocoa and chocolate include antioxidant properties, reduced blood pressure via the induction of nitric-oxide (NO)-dependent vasodilation in men, improved endothelial function, increased insulin sensitivity, decreased platelet activation and function, as well as modulated immune function and inflammation. Furthermore, chocolate has been reported to release phenylethylamine and serotonin into the human system, producing some aphrodisiac and mood-lifting effects. Since these claims could have implications for the consumption levels of cocoa and chocolate products on the global market, understanding the critical factors involved and their potential benefits are currently thought to be of great importance to consumers.Item Cocoa Fermentation: Chocolate Flavor Quality(2010) Ohene Afoakwa, E.; Alistair, P.Chocolate aroma and flavor attributes not only originate in precursor compounds present in cocoa beans, but are generated during fermentation and drying and transformed into desirable odor notes in the manufacturing process. Complex biochemical modifications of bean constituents are further altered by thermal reactions in the roasting and conching steps and during alkalization leading to the development of the finished flavor character; however, the extent to which fermentation component influences chocolate flavor formation and the relationships contributing to final flavor quality are not clear. With increasing specialty niche products in chocolate confectionery area, greater understanding of factors contributing to variations in flavor character during cocoa fermentation has significant commercial implications.Item Comparison of rheological models for determining dark chocolate viscosity(2009) Ohene Afoakwa, E.; Alistair, P.; Fowler, M.; Vieira, J.Parameters in chocolate rheology, namely shear viscosity and yield stress, are important in manufacture and directly influenced by product particle size distribution (PSD) and composition. The Casson model was the standard confectionery industry strategy to quantify rheological properties of molten chocolate until in 2000, the International Confectionery Association recommended the use of interpolation data to describe viscosity. The two strategies are compared and correlated in defining rheological properties of molten dark chocolates prepared using different PSD, fat and lecithin content. Rheological parameters were determined using a shear rate-controlled rheometer and data examined using correlation, regression and principal component analyses to establish their inter-relationships. Correlation and regression analyses showed high correlation (r = 0.89–1.00) and regression coefficients (R2 = 0.84–1.00). The newer International Confectionery Association technique gave higher correlation and regression coefficients than the Casson model, but multivariate principal component analysis showed that the two models were highly related and either could effectively quantify dark chocolate viscosity parameters.Item Effects of particle size distribution and composition on rheological properties of dark chocolate(2007) Ohene Afoakwa, E.; Alistair, P.; Fowler, M.Control of chocolate viscosity is vital to its quality and production cost, and directly influenced by solids particle size distribution (PSD) and composition. Effects of PSD and composition on rheological properties of molten dark chocolate were investigated by varying PSD [D90 (90% finer than this size) of 18, 25, 35 and 50 lm], fat 25, 30 and 35% and lecithin (0.3 and 0.5%) using a shear rate-controlled rheometer. PSD, fat and lecithin content significantly affected all rheological parameters, with significant interaction among factors. Increasing particles size gave significant reductions in Casson plastic viscosity, Casson yield value, yield stress, apparent viscosity and thixotropy, with greatest effect with 25% fat and 0.3% lecithin, which reduced with increasing fat and lecithin contents. Statistical analysis revealed that fat exerts the greatest effect on the variability in all the rheological properties followed by PSD and lecithin. PSD, fat and lecithin could be manipulated to control dark chocolate rheology, influencing quality whilst reducing production cost.Item "Effects of Polymeric Coating and Anti-Fungal Treatment on the Shrinkage Characteristics of Pineapple Fruits During Storage"(International Journal of Fruit Science 3(10): 309-322, 2010) Ayernor, S.G.; Ohene Afoakwa, E.; Bartels, P.K.; Budu, A.S.The combined effect of polymeric coating and antifungal treatment on the shrinkage characteristics of pineapple fruits during postharvest storage were evaluated. A 2×2×10 factorial experiment was performed with polymeric coating (0 and 5%) antifungal treatment (0 and 0.1%) and storage time (0-10 days) as the factors. The shrinkage evolution, shell colour break and crown withering index were evaluated using standard analytical methods. Regression models were developed to predict the valuables and their effect on shrinkage indices. The results showed that the polymeric coating, antifungal treatment, and storage time significantly (p <0.05) influenced shrinkage evolution, shell colour break and crown withering index of the fruits and very high regression coefficients (87.2-99.3%) were noted among the indices. The 5% polymeric coating with fungicide at 0.01% significantly arrested the shrinkage evolution, shell colour break and crown withering index under both low (4oC and ambient (20oC) storage. Shrinkage characteristics of pineapple fruits can therefore be effectively minimized by 5% polymeric coating and 0.01% anti-fungal treatment during postharvest storage.Item Effects of tempering and fat crystallisation behaviour on microstructure, mechanical properties and appearance in dark chocolate systems(2008) Ohene Afoakwa, E.; Alistair, P.; Fowler, M.; Vieira, J.Fat crystallisation behaviours in dark chocolates from varying particle size distribution (PSD) (D90 of 18, 25, 35 and 50 lm) was studied, yielding products from different temper regimes (optimal temper, over-temper and under-temper), and their effects on mechanical properties and appearance evaluated. Microstructures of derived products were determined using stereoscopic binocular microscopy. Wide variations in mechanical properties and appearance were noted in products from different particle size and temper regimes. Particle size (PS) was inversely related with texture and colour, with the greatest effects noted in hardness, stickiness and lightness at all temper regimes. Over-tempering caused significant increases in product hardness, stickiness with reduced gloss and darkening of product surfaces. Under-tempering induced fat bloom in products with consequential quality defects on texture, colour and surface gloss. Micrographs revealed variations in surface and internal crystal network structure and inter-particle interactions among tempered, over-tempered and under-tempered (bloomed) samples. Under-tempering caused whitening of both surface and internal periphery of products with effects on texture and appearance. Thus, attainment of optimal temper regime during pre-crystallisation of dark chocolate was central to the desired texture and appearance as both over-tempering and under-tempering resulted in quality defects affecting mechanical properties and appearance of products.Item Encyclopedia of Biotechnology in Agriculture and Food(Taylor & Francis Publishing Inc. (2010)., 2010) Ohene Afoakwa, E.; Alistair, P.Item Factors influencing rheological and textural qualities in chocolate - a review(2007) Ohene Afoakwa, E.; Alistair, P.; Fowler, M.): Chocolate, a complex emulsion, is a luxury food that during consumption evokes a range of stimuli that activate pleasure centres of the human brain. Central to chocolate quality is an appropriate melting behaviour so that products are solid at ambient temperature and on ingestion melt to undergo dissolution in oral saliva, with a final assessment of texture after phase inversion. Particle size distribution and ingredient com- position play important roles in shaping its rheological behaviour and sensory perception but are poorly understood. With opportunities for improvements in quality possible through im- proved and more transparent supply chain management, plant breeding strategies and new product development, associated with fair trade and development of niche premium quality products, there is a need for greater understanding of variablesItem Fat bloom development and structure-appearance relationships during storage of under-tempered dark chocolates(2009) Ohene Afoakwa, E.; Alistair, P.; Fowler, M.; Vieira, J.Fat bloom development and associated changes in microstructure, texture, appearance and melting properties were studied. Dark chocolates varying in particle size (PS) (D90of 18, 25, 35 and 50 μm) were processed and pre-crystallised to under-temper regime. Bloom was induced by storing products under ambient conditions (18 ± 2 °C, RH 50%) and changes in texture, surface whiteness, gloss and melting properties evaluated on cooling and after every 24 h in storage until reaching asymptotic values. Micro- structure of products were characterised during blooming using stereoscopic binocular microscopy. Measurements on texture and surface whiteness showed initial rapid increases with consequential reductions in gloss within the first 96 h, followed by gradually decreasing gradient until reaching asymptotic levels. Storage influenced melting properties (Tonset, Tend, Tpeakand DHmelt) in products causing polymorphic transformation from βIV to βVI within 72 h. Micrographs showed similar surface crystalline network structure and inter-particle interactions among products from different PS after tempering, and bloom initiation occurred within 24 h in storage resulting in appearance of both liquid and unstable fat on the surface of products. The unstable fat then re-crystallised during storage into more stable polymorphs and crystal growth was promoted by Ostwald ripening (larger crystals growing at the expense of smaller ones), with the appearance of white crystalline structure which spread gradually throughout the chocolate mass after 96 h. Product containing the largest PS (50 μm) showed the fastest fat bloom rate, with the smallest PS (18 μm) the least, attributed mainly to hydrodynamic forces by capillary action. It was hypothesised that fat bloom development was initiated by capillarity, followed by growth of re-crystallised fat by diffusion across the entire chocolate mass until fully bloomed.Item Flavor Formation and Character in Cocoa and Chocolate: A Critical Review(2008) Ohene Afoakwa, E.; Alistair, P.; Fowler, M.; Ryan, A.Chocolate characters not only originate in flavor precursors present in cocoa beans, but are generated during post-harvest treatments and transformed into desirable odor notes in the manufacturing processes. Complex biochemical modifications of bean constituents are further altered by thermal reactions in roasting and conching and in alkalization. However, the extent to which the inherent bean constituents from the cocoa genotype, environmental factors, post-harvest treatment, and processing technologies influence chocolate flavor formation and relationships with final flavor quality, has not been clear. With increasing speciality niche products in chocolate confectionery, greater understanding of factors contributing to the variations in flavor character would have significant commercial implications.Item Food Engineering Research Developments(Nova Science Publishers, Inc. (2007). (Hardcover), 2007) Ohene Afoakwa, E.Item Food Engineering Trends((In Press) Nova Science Publishers Inc. (2010)., 2010) Ohene Afoakwa, E.; Alistair, P.Item Influence of tempering and fat crystallization behaviours on microstructural and melting properties in dark chocolate systems(2008) Ohene Afoakwa, E.; Alistair, P.; Fowler, M.; Vieira, J.Particle size distribution (PSD) and temper influences on dark chocolate fat crystallization were studied using differential scanning calorimetry (DSC) and microscopy to establish relationships with their melt- ing properties and microstructure. Variations in PSD had no influence on crystallinity of products at all temper regimes. Particle size (PS) increases had limited effects on Tonset, Tpeak, and DHmelt independent of temper regime but significant decreases in Tend and Tindex were noted. Contrary, varying temper regime influenced the crystallinity and melting properties (Tend, Tindex and DHmelt) of products. Under-tempered chocolate showed widened crystal size distribution (CSD) with significant changes in Tend, Tindex and DHmelt of products. Over-tempering caused moderate increases in CSD and melting properties, with significant effect on Tend, Tindex and DHmelt but no changes were noted in Tonset, Tpeak of products. Fat–sugar melting profiles showed similar levels in all products independent of temper regime, suggesting fat and sugar components are present in similar amounts in under-, over- and optimally-tempered products. Micrographs revealed clear crystalline network structure and well defined inter-crystal networks among tempered and over-tempered samples. Under-tempered products showed re-arrangement and re-crystallization of unstable fat crystals to smaller numbers of larger agglomerates with formation of solid bridges between the crystalline network structures. Attainment of optimal temper regime during pre- crystallization of dark chocolate is necessary for the achievement of premium quality products and avoidance of defects in structure and melting character.Item Matrix effects on flavour volatiles release in dark chocolates varying in particle size distribution and fat content using GC–mass spectrometry and GC–olfactometry(2009) Ohene Afoakwa, E.; Alistair, P.; Fowler, M.; Ryan, A.Influences of matrix particle size distribution (PSD) (18, 25, 35 and 50 μm) and fat content (25%, 30% and 35%) on flavour release of dark chocolate volatiles were quantified by static headspace gas chromatography using GC–MS. Sixty-eight (68) flavour compounds were identified, comprising alcohols, aldehydes, esters, ketones, furans, pyrans, pyrazines, pyridines, pyroles, phenols, pyrones and thiozoles. From GC–olfactometry, 2-methylpropanal, 2-methylbutanal and 3-methylbutanal had chocolate notes. With cocoa/roasted/nutty notes were trimethyl-, tetramethyl-, 2,3-dimethyl-, 2,5-dimethyl-, 3(or 2),5- dimethyl-2(or 3)-ethyl- and 3,5(or 6)-diethyl-2-methylpyrazine and furfuralpyrrole. Compounds with fruity/floral notes included 3,7-dimethyl-1,6-octadien-3-ol and 5-ethenyltetrahydro-R,R,5-trimethyl- cis-2-furanmethanol. Caramel-like, sweet and honey notes were conferred by 2-phenylethanol, phenyl- acetaldehyde, 2-phenylethylacetate, 2,3,5-trimethyl-6-ethylpyrazine, 2-carboxaldehyde-1H-pyrrole, furancarboxaldehyde, furfuryl alcohol and 2,5-dimethyl-4-hydroxy-3(2H)furanone. There were direct relationships of fat content with 3-methylbutanal and branched pyrazines but inverse ones with 2-phen- ylethanol, furfuryl alcohol, methylpyrazine, phenylacetaldehyde, 2, 3, 5-trimethyl-6-ethylpyrazine and 2- carboxaldehyde-1-H-pyrrole. Particle size influenced higher alcohol, aldehyde, ester, ketone and pyrazine concentrations at all fat contents. A multivariate product space suggested flavour effects of the interacting factors.Item : Melamine Contamination of Infant Formula in China: The Causes, Food Safety Issues and Public Health Implications(2008) Ohene Afoakwa, E.Melamine - an industrial chemical - was recently found in infant formula in China but it has since spiralled to other food categories that use milk powder as an ingredient, such as chocolate, biscuits and eggs. As of September 21, 2008, a total of 52,857 cases of nephrolithiasis (and, in some instances, renal failure) had been reported in China linked to consumption of this contaminated powdered formula. There have been approximately 13,000 hospitalizations, and at least 4 deaths confirmed to date. The vast majority of illnesses involved children under the age of 3 years (82% < 2 years; 17% 2-3 years; 0.8% > 3 years; and no cases involved adults). The results of an investigation conducted in China indicated that Chinese-produced powdered infant formula was linked to these illnesses; no cases were associated with liquid infant formula. An investigation of powdered formulas was conducted nationally by China's General Administration of Quality Supervision, Inspection and Quarantine (AQSIQ) and revealed contaminant ion of powdered formulas produced by 22 companies. Test results conducted in China on samples of the powdered infant formula showed that they contained a wide range of concentrations (0.1 ppm to greater than 2,500 ppm melamine powder. In addition, other countries have reported detection of melamine in other product categories, such as confections and beverages. Generally, there are available analytical methods that can reliably detect a level of 1 ppm melamine in some food matrices.