Contents
01.12.2018.
Professional paper
Consumer awareness of the use of food labels in Lagos state, Nigeria
The increase in relative level of education and the growing middle-class income earners in Nigeria have made packaged food items attractive to consumers. These foods provide handy, nutritious and convenient food for consumers; however, they also come with public health concerns. From a policy perspective, food labelling can gauge consumers’ response to the safety conditions of packaged food. However, understanding consumers’ awareness and the use of food label information has attracted little research attention in many developing countries in sub-Saharan Africa. In this study, we investigate consumers’ awareness of the use of food safety labels in Lagos state, Nigeria. We used primary data collected using pretested structured questionnaire from 220 food shoppers who bought pre-packaged foods. A two-stage sampling technique was used to select the respondents. Consumers’ awareness and use of food safety information was revealed using descriptive statistics; Ordinal Regression Analysis was used to examine the socioeconomic factors determining the frequency of reading food safety labels. The study therefore recommends that there should be continuous awareness campaigns on the importance of food labels in ensuring safety and food producers should make sure their food labels are legible.
Samuel T. Danilola, Olubunmi A. Omotesho, Jubril Animashaun
01.12.2018.
Professional paper
Study of the self-stabilization ability of Tzatziki (a traditional Greek ready-to-eat deli salad)
Traditional Greek yogurt-based salad Tzatziki is one of the most popular ready-to-eat deli salads in Greece. The objective of this study was to estimate the microbial stability of Tzatziki, with and without chemical preservatives, using a rapid method. Determination of the microbial count was carried out using the bioluminescence method (ATP) and traditional microbiological analysis, plate-counting method (CFU) in various batches of the final product of Tzatziki. The results showed that the Tzatziki salad without preservatives initially gave higher relative light units (RLU) values (79,532) than the same salad with preservatives (43,198) because the potassium sorbate and the sodium benzoate, used in recipe, appeared to suspend the action of microorganisms. After incubation in two different substrates, MacConkey and Sabouraud, the Tzatziki salad without preservatives gave higher RLU values (9,488 and 16,176, respectively) than the salad with preservatives (12,780 and 12,005, respectively). In the two selective substrates, differences appeared between the two methods of microbial count (RLU and CFU). While RLU values were roughly at the same level, the CFU values presented significant differences (p < 0.05). It was also shown that there was a strong correlation (R2 = 0.93-0.95) between bacterial counts estimated by traditional CFU and ATP methods. As expected, the dominant microbial population in Tzatziki was Lactobacillus spp., originated from yogurt. Coliforms and yeasts were not able to survive in this environment. Generally, according to the results, Greek traditional Tzatziki salad was a microbial stable product and the bioluminescence method could be a rapid method to determine its microbial state.
Stavros Lalas, Vassilis Athanasiadis, Ioanna Karageorgou, Eleni Bozinou, Vassilis G. Dourtoglou
01.12.2018.
Professional paper
Stability of vitamin C in broccoli at different storage conditions
In this study, the retention of vitamin C in fresh broccoli stored at different temperatures (i.e. chiller, room, cooking, and roasting or baking; 5-120°C) was investigated. The thermal stability of vitamin C in broccoli was analysed at 5, 20, 45, 60, 70, 80, 110, and 120°C. The vitamin C content was measured by the indophenol titration method. Vitamin C was affected negatively at all stored temperatures. The degradation of vitamin C was modelled by first-order reaction kinetics and the reaction rate constants were observed as 9.03×10-8 and 5.65×10-3 s-1 when stored at 5°C and 120°C, respectively. The activation energy was estimated as 74.2 kJ/mol within the temperature range used in this study. The lowest decay of vitamin C was observed during the chilling condition. The data on retention of vitamin C in broccoli could be used to determine their stability, when stored as raw, and when heated at different temperatures.
Nasser Al-Habsi, Sithara Suresh, Amani Al-Yhmedi, Marwa Al-Shoryani, Mostafa I. Waly, Mohammad Shafiur Rahman
01.12.2018.
Professional paper
Optimization conditions of UV-C radiation combined with ultrasound-assisted extraction of cherry tomato (Lycopersicon esculentum) lycopene extract
The aim of this work was to study the effect of UV-C radiation on ultrasound assisted extraction (UAE) of cherry tomato bioactive compounds. Cherry tomatoes were exposed to two UV-C radiation doses (0.5 and 1.0 J cm-²) and stored at 20 ± 0.5 °C for 7 days. Next, they were lyophilized, and the bioactive compounds were extracted by UAE at 20 KHz. To evaluate the effectiveness of the extraction process of the bioactive compounds, a CCRD (central composite rotational design) was used together with RSM (response surface methodology), for extraction times from 4 to 12 minutes and concentrations (g of lyophilized product / L of ethanol) of 1:10, 1:20 and 1:30. The extracts obtained from the irradiated tomatoes presented 5.8 times more lycopene content than the controls and higher antioxidant activity was obtained for 4 and 8 min, in the concentrations 1:10 and 1:20 (m v-1). Trough numerical model optimization, optimal extraction conditions were obtained. The results demonstrated that by previously irradiating tomatoes with UV-C, the UAE yielded considerably higher amounts of lycopene and other bioactives.
Alexandre R. Lima, Nathana L. Cristofoli, Josamaique G. Veneral, Alcilene R. M. Fritz, Margarida C. Vieira
01.12.2018.
Professional paper
Use of response surface methodology (RSM) for composite blends of low grade broken rice fractions and full-fat soybean flour by a twin-screw extrusion cooking process
In this study, seventeen (17) composite blends of broken rice fractions and full-fat soybean, formulated using response surface methodology and central composite design within a range of barrel temperatures (100-140 °C), initial feed moisture content (15-25%) and soybean composition (8-24%), were extruded with a twin-screw extruder and the expansion and color indices were optimized. The results indicated a significant (p<0.05) effect of extrusion conditions on the responses. Fitted predictive models had coefficients of 88.9%, 95.7%, 97.3%, 95.4% and 95.2%, respectively, for expansion index, bulk density, lightness, redness and yellowness. The p-value and lack-of-fit tests of the models could well explain the observed variability and therefore could be used to establish production setting for the twin-screw extruder. The optimum extrusion conditions were found to be 130 °C (barrel temperature), 20% (feed moisture level) and 23% feed soybean composition and optimum responses in terms of bulk density, expansion index, lightness, redness and yellowness chroma indices were 0.21 g cm-3, 128.9%, 17.1, 3.13 and 24.5 respectively. This indicates that optimum conditions can be established in twin-screw extrusion cooking of broken rice fractions and full-fat soybean composite blends that can result in product of low bulk and maximum expansion with a satisfactory light yellow product color that can be used to produce products that valorize broken rice and reduce qualitative postharvest loss.
Nahemiah Danbaba, Iro Nkama, Mamudu Halidu Badau
01.12.2018.
Professional paper
Moisture sorption isotherm and thermal characteristics of freeze-dried tuna
Water activity is considered an important factor in assessing the stability of food. Understanding the relationship between water activity and equilibrium moisture content (moisture sorption isotherm) benefits food processing in terms of modeling of drying and estimation of shelf life. In addition, glass transition helps to quantify molecular mobility which helps in determining the stability of food. The aim of this study was to determine the moisture sorption isotherm and thermal characteristics of freeze-dried tuna. These characteristics will help in determining the monolayer moisture and glassy state of the product, at which food is considered most stable. Moisture sorption isotherm at 20°C and thermal characteristics (over a wide temperature range i.e. from -90 to 250 °C) of freeze-dried tuna flesh were measured. Isotherm data were modeled by BET (Brunauer-Emmett-Teller) and GAB (Guggenheim-Anderson–De Boer) models. The GAB and BET monolayer water values were determined as 0.052 and 0.089 g g-1 dry-solids (dry-basis), respectively. In the case of samples at moisture contents above 0.10 g g-1 (wet basis), DSC (Differential Scanning Calorimetry) thermograms showed two-step state changes (i.e. two glass transitions), one exothermic peak (i.e. molecular ordering) and another endothermic peak (i.e. solids-melting). However, the sample at moisture content of 0.046 g g-1 showed three-step state changes (i.e. three glass transitions). The multiple glass transition could be explained by the natural heterogeneity of tuna flesh and inhomogeneity due to molecular incompatibility of the different compositions. The moisture content did not affect the first glass transition temperature nor the exothermic peak (p>0.05), whereas the third glass transition temperature decreased (i.e. plasticized) with increasing moisture content (p<0.05). The solids-melting peak temperature decreased, and enthalpy increased with decreasing moisture content (p<0.05).
Mohammad Shafiur Rahman, Mohammed Khalfan Al-Khusaibi, Kutaila Abbas AL-Farsi, Ismail Mohamed Al-Bulushi, Aisha Abushelaibi, Nasser Al-Habsi
18.04.2019.
Original scientific paper
Moisture sorption isotherm and thermal characteristics of freeze-dried tuna
Water activity is considered an important factor in assessing the stability of food. Understanding the relationship between water activity and equilibrium moisture content (moisture sorption isotherm) benefits food processing in terms of modeling of drying and estimation of shelf life. In addition, glass transition helps to quantify molecular mobility which helps in determining the stability of food. The aim of this study was to determine the moisture sorption isotherm and thermal characteristics of freezedried tuna. These characteristics will help in determining the monolayer moisture and glassy state of the product, at which food is considered most stable. Moisture sorption isotherm at 20 oC and thermal characteristics (over a wide temperature range i.e. from -90 to 250 oC) of freeze-dried tuna flesh were measured. Isotherm data were modeled by BET (Brunauer-Emmett-Teller) and GAB (GuggenheimAnderson–De Boer) models. The GAB and BET monolayer water values were determined as 0.052 and 0.089 g g−1 dry-solids (dry-basis), respectively. In the case of samples at moisture contents above 0.10 g g−1 (wet basis), DSC (Differential Scanning Calorimetry) thermograms showed two-step state changes (i.e. two glass transitions), one exothermic peak (i.e. molecular ordering) and another endothermic peak (i.e. solids-melting). However, the sample at moisture content of 0.046 g g−1 showed three-step state changes (i.e. three glass transitions). The multiple glass transition could be explained by the natural heterogeneity of tuna flesh and inhomogeneity due to molecular incompatibility of the different compositions. The moisture content did not affect the first glass transition temperature nor the exothermic peak (p>0.05), whereas the third glass transition temperature decreased (i.e. plasticized) with increasing moisture content (p<0.05). The solids-melting peak temperature decreased, and enthalpy increased with decreasing moisture content (p<0.05).
Mohammad Shafiur Rahman, Mohammed Al-Khusaibi, Kutaila Abbas AL-Farsi, Ismail Mohamed Al-Bulushi, Aisha Abushelaibi, Nasser Al-Habsi
18.04.2019.
Original scientific paper
Nutritional and antioxidant potential of rice flour enriched with kersting’s groundnut (Kerstingiella geocarpa) and lemon pomace
This study was designed to enhance the nutritional quality, antioxidant properties and product utilization potentials of locally produced ‘Igbemo’ rice flour by adding Kersting’s groundnut and lemon pomace. Kersting’s groundnut is an underutilized legume while lemon pomace is a byproduct of lemon utilization; both meant to enhance the protein quality, antioxidant potential and fibre contents of the composite flour. The dependent variables were minerals composition, amino acid profile, antioxidants and antinutrients properties, in-vitro protein digestibility and in-vitro carbohydrate digestibility. The result showed that blends with higher lemon pomace of 10.00 g had the best calcium, iron, potassium and magnesium contents and antioxidant contents, while blends with highest Kersting’s groundnut (20.00 g) had the best zinc content. The anti-nutrients in the blends were generally low and safe for consumption.
Olugbenga Awolu, Magoh A. Osigwe
01.12.2018.
Professional paper
Moisture sorption isotherm and thermodynamic properties of jamun (Syzygium cumini L.) powder made from jamun pulp and seed
The present work aimed to: i) find the suitable proportion, based on sensory evaluation, of microwave-convective hot air dried jamun (Syzygium cumini L.) pulp and seed kernel powder to be mixed for the preparation of jamun powder (JP); ii) generate and model the moisture sorption isotherm (MSI) of JP; and iii) estimate net isosteric heat of sorption (qst), spreading pressure (φ), net integral enthalpy (Qin), and net integral entropy (Sin). To formulate JP, the proportion (w/w, db) comprising 2% kernel and 98% pulp powder was the most desirable. The Peleg model was the best fit to MSI of JP. The qst decreased following linear relationship from 11.02 kJ. mol-1 at 5% equilibrium moisture content (EMC) to 0.27 kJ. mol-1 at 30% EMC. The φ increased with increase in water activity and decreased with increase in temperature from 25 ºC to 35 ºC, and the values of φ at 45 ºC were even higher than at 25 ºC. Net integral enthalpy (Qin) initially decreased till 6% moisture content in JP and displayed an increasing trend with further increase in moisture content. On the contrary, Sin, kept on decreasing continually with increasing moisture content. The moisture zone of 7-11% was considered safe for storage for storage of JP within the temperature range of 45-25 ºC.
Indira Dey Paul, Madhusweta Das
01.12.2018.
Professional paper
Potentials of African nutmeg (Monodora myristica) as a flavourant in cookie production
African nutmeg, a possible local substitute for a commercial food flavourant, remains largely underutilized in Nigeria. Its application potential in cookie production was investigated in this study. African nutmeg (Monodora myristica) seed flour (ANM) was produced using standard method. The flour was substituted for vanilla flavour (VFL) in ratio of 0, 1, 2, 3, and 3.5 g and functional properties of the flour blends (water absorption capacity (WAC), oil absorption capacity (OAC), and bulk density) were determined, using standard methods. Cookies were developed and characterized chemically, physically (colour) and organoleptically using the AOAC method, a colourimeter and sensorypanellistsrespectively. Data were analysed using ANOVA at p<0.05. Replacement of vanilla with African nutmeg had no significant effect on bulk density (0.62g/cm3 – 0.68 g/cm3), but significantly affected WAC (133-142%) and OAC (147-156%) of flour blends. Crude protein (9.44-15.49%), crude fat (3.17-6.50%), total ash (2-2.73%) and crude fibre (0.12-0.23%) contents of the cookie increased, whilst metabolizable energy (385.33-367kcal) decreased. There were reductions in pH (6.83-6.53) and TSS (5.80-1.20). Brown index of the snack increased with addition of nutmeg. Antioxidant indicators (flavonoids, DPPH and phenol) varied among cookie samples. Antinutrients, saponin, tannin and oxalate, were within tolerable limits. All cookie samples were judged acceptable by the panellists, with SLZ being the most acceptable. An acceptable and nutritious snack was produced at 100% replacement. M. myristica seed could serve as substitute for vanilla in the production of cookies and other related snacks.
Kazeem K. Olatoye, Omololo O. Fapojuwo, Joshu A. Olorunshola, Julianah O. Ayorinde
