Contents
18.04.2017.
Original scientific paper
Effect of pretreatments and processing conditions on anti-nutritional factors in climbing bean flours
It is difficult for many Rwandans to utilize climbing bean seeds (Phaseolus vulgaris L.) mainly because of longer cooking time (2 hours) and the high consumption of basic fuel. Climbing beans also contain anti-nutritional factors such tannins, phytates, trypsin inhibitors and phytohemagglutinins that limit nutrient absorption. One way to solve this problem is to utilize the flour of climbing beans made from different treatments and processing methods. In this study, climbing beans were pre-treated by soaking them in water for 24 hours, soaking in 2% sodium bicarbonate solution and steam blanching for 10 minutes. After that, pre-treated climbing beans were processed into flours by processing methods such as roasting, cooking and germination where anti-nutritional factors were reduced. The pretreatments did not significantly (p>0.05) affect phytates in climbing bean flours but processing conditions significantly (p<0.05) reduced it. Pretreatments and processing conditions significantly (p<0.05) reduced tannin content. The pretreatments followed by different processing conditions significantly (p<0.05) decreased trypsin inhibitors content. The great significant decrease in phytohemagglutinins content was observed in pretreatment followed by different processing methods. All pretreatments and processing conditions effectively decreased anti-nutritional factors at low level. However, pretreatments or untreated followed by germination and roasting were found to be the most and the least effective respectively. Making flour from germinated climbing bean seeds is a good option for sustainable food processing as it reduces anti-nutritional factors. It is an inexpensive method in terms of time, energy and fuel for Rwandan households, restaurants and industries where climbing bean seeds are integral part of daily meal.
Emmanuel Mugabo, Emmanuel Ohene Afoakwa, George Annor, Bernard RWUBATSE
18.04.2017.
Original scientific paper
Extrusion cooking technology: Principal mechanism and effect on direct expanded snacks – An overview
The snack industry is one of the fastest growing food sectors and is an important contributor within the global convenience food market. Nowadays snacks and convenience foods are also consumed regularly in India. Properly designed convenience foods can make an important contribution to nutrition in societies where social changes are altering traditional patterns of food preparation. Extrusion cooking as a popular means of preparing snack foods based on cereals and plant protein foodstuff has elicited considerable interest and attention over the past 30 years. Several studies on the extrusion of cereals and pulses, using various proportions, have been conducted because blends of cereals and pulses produce protein enriched products. Special importance is placed on the physicochemical and chemical modifications of protein, starch and dietary fibre. Extruded products can be categorized for a particular application based on their functional properties such as water absorption and water solubility index, expansion ratio, bulk density and viscosity of the dough. Therefore, the literature was reviewed for effect of extrusion processing on product parameters, and nutritional and anti-nutritional properties of extruded products.
AJITA TIWARI, Jha S. K.
18.04.2017.
Original scientific paper
Vacuum-assisted microwave drying characteristics of green bell pepper
Chopped green bell pepper pieces were blanched (95 °C, 5 min) and chemically pretreated (1% potassium metabisulphite solution, 25 min at room temperature) before drying in hot air dryer (HAD) at various temperature ranges (60 – 80 °C). Three vacuum levels (200, 400, 600 mm Hg) and microwave power levels (100, 200, 300 W) were also used to dry green bell pepper samples in a vacuum-assisted microwave (VAM) (2.45 GHz, 0.8 kW) dryer. VAM drying methods offered a maximum reduction by four to five times in drying time as compared to that in HAD. The logarithmic model was found to have the best fit based on high R2 and small values of reduced χ 2 and RMSE. VAM method has higher values for effective moisture diffusivity (Deff ) and lower values for activation energy (Ea), in comparison to the HAD method.
Vivek Kumar, Shanker L. Shrivastava
01.12.2016.
Professional paper
Evaluation of physical, milling and cooking properties of four new rice (Oryza sativa L.) varieties in Nigeria
This comparative study investigated some physical, milling and cooking properties of four new rice varieties (FARO 44, FARO 52, FARO 60 and FARO 61) in Nigeria. The varieties were processed into white rice and their properties analyzed separately using standard procedures. Results showed that paddy length, paddy-length-to-width-ratio, equivalent diameter, sphericity, grain volume, aspect ratio, thousand paddy grain weight, milled rice length, milled rice width, milled rice length to width ratio, milling recovery, head milled rice, broken milled rice, L*, a*, b*, elongation ratio, cooked-rice-length-to-breadth-ratio, water uptake ratio and cooking time were significantly different (p<0.05) for all the varieties. Milling recovery was found to vary from 65.3 to 68.33%; with FARO 60 having the highest head milled rice. It was observed that FARO 44 had the longest cooking time, elongation ratio and cooked rice length/breadth ratio while FARO 61 was found to have the highest water uptake ratio. There was significant positive correlation (r = 0.824) between percentage head milled rice and milling recovery while negative correlation existed between cooking time and L* (r= - 0.711). This information could be exploited by rice processors in the post-harvest processing of the varieties.
Mayowa S. Sanusi, Rahman Akinoso, Nahemiah Danbaba
01.12.2016.
Professional paper
Drying characteristics of zucchini and empirical modeling of its drying process
The aim of the study was to dry zucchini (Cucurbita pepo) by two different methods (convective hot-air (CHD) and microwave-assisted drying (MWD)). The effect of air temperature (60, 70 and 80°C), microwave (MW) power (180, 360, 540 W) and sample thickness (5 and 10 mm) on some drying characteristics of zucchini were investigated. Thirteen mathematical models available in the literature were fitted to the experimental moisture ratio data. The coefficients of the models were determined by non-linear regression analysis. It was determined that the model that fits the moisture ratio data the best varies at different drying conditions. Increasing drying temperature and MW power and reducing sample thickness improved the drying rate and drying time. Drying in microwave has reduced the drying time by 52-64% for zucchini. It was found that the effective moisture diffusivities increased with increasing temperature and MW power. MWD samples had better rehydration ratios compared to ones dried only in tray drier for 5 mm thickness.
Naciye Kutlu, Asli Isci
01.12.2016.
Professional paper
Impact of selected polyphenolics on the structural properties of model lipid membranes – a review
This review is a presentation of data gathered on the interactions of several polyphenolics (i.e., phenolic acids, stilbenes, flavonoids) with lipid bilayers of different lipid compositions. These polyphenolics have been investigated through a combination of fluorescence spectroscopy, electron paramagnetic resonance spectroscopy, and differential scanning calorimetry, to detect changes in membrane fluidity. Among the investigated phenolic acids, the least polar phenolic acid, p-coumaric acid, has the greatest effect on lipid membrane structure. It appears to have a greater ability to cross membranes by passive transport than more polar phenolic acids. On the other hand, among the flavonoids that have been studied, the anthocyanins cyanidin 3-glucoside and its aglycone are inactive. All of the flavonols tested, except for epigallocatechin-3-gallate, promote small decreases in membrane fluidity. Computer simulation of electron paramagnetic resonance spectra for flavonoids indicated two or three regions in the phosphatidylcholine/ phosphatidylserine (2.4:1) membrane with different fluidity characteristics. The effects of the different flavonoids are correlated to their structural characteristics, whereby even the difference in one -OH group can be important, as can the number of H-bonds they form. The role of membrane composition and flavonoid structure in these interactions with lipid membranes are of great importance for bioavailability of these compounds and for their biological effects in an organism
Nataša P. Ulrih, Ajda Ota, Veronika Abram
01.12.2016.
Professional paper
Effect of Grewia venusta FRESEN mucilage on the proximate composition, physical and sensory properties of bread produced from wheat and cassava composite flours
Wheat and cassava composite breads are generally associated with volume and textural defects in contrast with the traditional wheat based variants. Efforts to mitigate this challenge through use of synthetic additives have been unsuccessful owing to safety concerns. The objective of this study was to explore Grewia venusta mucilage as a potential natural additive in wheat-cassava composite bread production. Sweet cassava flour was used to replace wheat flour at 100: 0 (control), 90:10, 80:20 and 70:30% ratios in bread making. Aqueous extract of G. venusta stem bark was oven dried (50±3 oC), milled and added at 0, 1.0 and 2.0% (w/w) to the flour mixtures. These, along with other conventional inputs were mixed, and used to produce bread. Proximate compositions, physical and sensory properties of the bread loaves were evaluated. Cassava flour inclusion resulted in significant (P≤0.05) decrease in the protein content of the control from 18.1% to 12.1% (90:10%), 11.5% (80:20%) and 9.9% (70:30%). Addition of mucilage marginally increased the protein and dietary fibre contents of the loaves. Loaves containing 1-2% mucilage were more regular in shape with smoother crust than those without mucilage. Cassava flour addition at 10%, 20% and 30% decreased loaf height from 6.0 cm to 5.8 cm, 5.7 cm and 5.5 cm, as well as loaf volume from 815.5 cm3 to 783.1 cm3, 776.8 cm3 and 744.5 cm3, respectively. Mucilage inclusion resulted in increased heights and volumes of the loaves and reduced weights of loaf fragments upon slicing. The mucilage significantly improved the texture of the bread loaves.
Arubi P. Alobo, Gibson L. Arueya
01.12.2016.
Professional paper
Microbial quality and shelf life prediction of vacuum-packaged ready to eat beef rounds containing gum arabic
Research has shown that gum arabic from Acacia senegal var. kerensis can be used in beef rounds, at a level of 2.5% of the formulated product weight, as a binder and texture modifier. However, the effect of gum arabic addition on the microbial quality and shelf life of the resulting meat product has not yet been reported. Thus, the objective of this work was to study the microbial quality of beef rounds containing 2.5% gum arabic and to study shelf life based on the growth parameters of Total Viable Counts (TVC) and Lactic Acid Bacteria (LAB). Beef round samples were injected at 30% with curing brines containing gum arabic and cooked through boiling. The growth kinetics of LAB and TVC were studied for vacuum packaged sliced beef round samples stored at 7 oC and 15 oC for a period of 21 days. Baranyi and modified Gompertz models were used to fit the LAB and TVC data obtained using DMFit. Results of microbial analysis indicated that coliforms, yeasts and molds as well as pathogenic bacteria; Salmonella, Escherichia coli, and Staphylococcus aureus, were below detection limit. In addition, TVC and LAB were found to be 1.87 ± 1.09 and 1.25 ± 0.75 Log 10 CFU g-1, respectively. The results of accuracy analysis showed that both the Baranyi and modified Gompertz models were adequate in representing the bacterial growth in beef rounds injected with curing brines containing gum arabic. The predicted shelf life was found to be between 84.3 – 88.1 h and 158.0 – 173.1 h at 15 oC and 7 oC, respectively.
Johnson K. Mwove, Symon M. Mahungu, Lilian A. Gogo, Ben N. Chikamai, Mary Omwamba
01.12.2016.
Professional paper
Rheological properties of traditional balsamic vinegar: New insights and markers for objective and perceived quality
The molecular structure of Traditional Balsamic Vinegar (TBV) undergoes shear-induced and time-dependent jamming transitions due to the high solute concentration and self-assembling phenomena of high molecular size melanoidins with very-long relaxation times (12 years at least or more than 25). The purpose of this work was to perform a descriptive and quantitativeevaluation of relationships between rheological properties, vinegar composition, and perceptual assessment of sensory properties according to the official sensory procedure. With this aim, vinegars having quality traits matching legal requirements for the PDO designation were analyzed for their reducing sugars (glucose and fructose), volatile acidity, fixed acidity, pH, Brix degree, and density as well as for their flow behaviour and dynamic viscosity over a wide range of shear rates. Results showed that flow behaviour of TBV was affected by jamming properties over wide-scale ranges of shear rate producing flow instability below a shear rate of 60s-1. Homogeneous, continuous flow was found at medium-high shear rates with thickening and/or thinning traits. A common onset for the structure scaling was mathematically estimated to occur close to when the density was 1.32 gmL-1. Comparative analysis of rheological, compositional and sensory properties suggested that the colloidal jamming of the vinegar melanoidins dominated the total olfactive and gustative stimuli, and determined the classification of the vinegars that had a higher dynamic viscosity but more homogeneous flow as being of the highest commercial quality category. A robust statistical model was proposed encoding for the top-down decision-making process for quality assignment according to the official sensory procedure, using composition and flow properties as predictor variables.
Pasquale M. Falcone, Elisa Sabatinelli, Federico Lemmetti, Paolo Giudici
01.12.2016.
Professional paper
Effect of tuna skin gelatin-based coating enriched with seaweed extracts on the quality of tuna fillets during storage at 4 °C
Nowadays, consumers demand high quality food products with an extended shelf-life without chemical additives. Edible coatings (EC) containing natural compounds are a promising preservation technology for raw seafood without compromising fresh-like appeal and nutritional content.The aim of this work was to evaluate the effect of Thunnus obesus skin gelatin-based EC containing Codium spp. or Fucus vesiculosus extracts on raw tuna preservation. Three gelatin-based EC (gelatin (5 %) + glycerol (25 %); gelatin (5 %) + Codium spp. (1 %) + glycerol (25 %); gelatin (5 %) + Fucus vesiculosus (1 %) + glycerol (25 %)) were applied directly on the surface of tuna fillets. Functional properties of gelatin and gelatin-based EC containing seaweed extracts were also studied. The gelatin was extracted by an acid-swelling process in the presence/absence of pepsin, followed by subsequent heating/refrigeration, after a pre-treatment with NaOH. The type of acid, temperature and concentration of NaOH greatly influence the process yield. The higher extraction yield was achieved using acetic acid in the presence of pepsin by subsequent refrigeration, especially when skins were previously treated with NaOH (0.2 M). Tuna quality was assessed over 12 days of storage at 4 ± 1 °C in terms of chemical and microbial indices. Results showed that tuna skin gelatin-based EC avoids tuna deterioration. Microbial growth, assessed by total viable counts, and total volatile basic nitrogen were maintained below the maximum limits recommended, contrarily to the control. Additionally, the use of EC increased the stability of red colour during storage.
Milene Vala, Ana Augusto, André Horta, Susana Mendes, Maria M. Gil