Contents
01.12.2013.
Professional paper
Determination of the antioxidant capacity, total phenolic and flavonoid contents of seeds from three commercial varieties of culinary dates
Date seeds are a major waste product of the date industry that could offer potentially valuable material for the production of useful food ingredients. The aim of the present study was to investigate the seeds of three date varieties of the UK market (Deglet Nour, Khouat Allig, and Zahidi) for their proximate composition, total phenolic (TPC), total flavonoid (TFC) contents and total antioxidant capacity (TAC) with a view to their eventual industrial application. Carbohydrates were present in the highest concentrations varying between 74.13 and 76.54 g 100 g-1 of date seed powder (DSP) on dry weight (DW) basis, followed in descending order by fats (7.64-8.84 g 100 g-1) and proteins (4.35-5.51 g 100 g-1). Potassium was found in high amounts with values ranging between 280.55 and 293.13 mg 100 g-1. The majority of the total phenolic content (2058-2984 mg GAE 100 g-1) was assumed to be composed of flavonoids (1271-1932 mg CAE 100 g-1). These families of dietary phenolics may be the major ones responsible for the high antioxidant capacity reported in date seeds, which varied from 12540 and 27699 µmol TE 100 g-1. These results suggest that date seeds can be considered a potential raw material for natural, active ingredients for food applications as well as an unexplored source of novel nutraceuticals and dietary supplements.
Suresh Krishnamoorthy, Jacopo Mistrello, Sameera Dewundara Sirisena, Abdollah Ghavami, Richard James Marshall
01.12.2013.
Professional paper
Peer-teaching in the food chemistry laboratory: student-produced experiments, peer and audio feedback, and integration of employability skills
This paper describes the author’s experience over the last several years of implementing an alternative Food Chemistry laboratory practical model for a group of third-year BSc Nutraceuticals students. The initial main objectives were to prepare students for the more independent final-year research project; to incorporate innovative approaches to feedback; and to integrate key employability skills into the curriculum. These were achieved through building the skills required to ultimately allow students working in groups to research, design and run a laboratory for their class. The first year of the project involved innovative approaches to feedback, including weekly feedback sessions, report checklists and audio feedback podcasts. Student evaluation after one year suggested the case group felt more prepared for final-year research projects and work placement owing to the redesign of the laboratory assessment. This, together with general positive feedback across several indicators, was proof of concept, and was a foundation for an improved model. The improvements related to the organisation and management of the project, but the same pedagogical approach has been retained. The second year saw the introduction of a more rigorous and easier to manage peer evaluation though use of the online Comprehensive Assessment for Team-Member Effectiveness (CATME) tool. The most recent revision has included a Project Wiki hosted on Blackboard to facilitate the organisation, communication, assessment and feedback of student-generated resources.More recently, the final-year students who had participated in the peer-teaching Food Chemistry labs when in third year have been evaluated. This evaluation took place following their research projects, and suggests that the peer-teaching model better prepared them for these activities, compared to traditional laboratories.
Julie Lisa Dunne
01.12.2012.
Professional paper
Mechanical properties of rough and dehulled rice during drying
This work aimed to determine the mechanical properties of rough and dehulled rice grains, for different moisture contents, by obtaining their rupture force, deformation, maximum compression force and proportional deformity modulus under a compression test. Rice grains, with moisture content varying from 0.12 to 0.30 (d.b.), were subject to an uniaxial compression in order to analyze these properties. On reducting moisture content the rupture force increased from 37.2 to 70.6 N for dehulled rice and 48.0 to 79.5 N for rough rice. The average compression force varied from 131 to 171 N for dehulled rice and 203 to 283 N for rough rice. The value range of proportional deformity modulus was from 5.5 x 109 to 7.4 x 109 Pa for dehulled rice and 9.5 x 109 to 12.3 x 109 Pa for rough rice. Rough rice presented more resistance to compression compared to dehulled rice.
Osvaldo Resende, Paulo César Corrêa, Gabriel Henrique Horta de Oliveira, André Luis Duarte Goneli, Carmen Jarén
01.12.2012.
Professional paper
Viability of the microencapsulation of a casein hydrolysate in lipid microparticles of cupuacu butter and stearic acid
Solid lipid microparticles produced with a mixture of cupuacu butter and stearic acid were used to microencapsulate a commercial casein hydrolysate (Hyprol 8052). The composition of the lipid matrix used for the production of the lipid microparticles was chosen according to data on the wide angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC) of bulk lipid mixtures, which indicated that the presence of 10 % cupuacu butter was sufficient to significantly change the crystalline arrangement of pure stearic acid. Preliminary tests indicated that a minimum proportion of 4 % of surfactant (polysorbate 80) was necessary to produce empty spherical lipid particles with average diameters below 10 mm. The lipid microparticles were produced using 20 % cupuacu butter and 80 % stearic acid and then stabilized with 4 % of polysorbate 80, exhibiting an encapsulation efficiency of approximately 74 % of the casein hydrolysate. The melting temperature of the casein hydrolysate-loaded lipid microparticles was detected at 65.2 °C, demonstrating that the particles were solid at room temperature as expected and indicating that the incorporation of peptides had not affected their thermal behavior. After 25 days of storage, however, there was a release of approximately 30 % of the initial amount of encapsulated casein hydrolysate. This release was not thought to have been caused by the liberation of encapsulated casein hydrolysate. Instead, it was attributed to the possible desorption of the adsorbed peptides present on the surface of the lipid microparticles.
Samantha Cristina Pinho, Janaina Costa Da Silva
01.12.2012.
Professional paper
Physical properties of honeys produced in the Northeast of Brazil
The aim of this work was to study the rheological, thermal and some other physical-chemical properties of selected honeys produced in the Northeast of Brazil. Two samples were produced by native “Jandaira” bees (Melipona subnitida) and ten other samples by Africanized bees (Apis mellifera). The samples were analyzed for pH, water activity (aW), soluble solids and water content. Viscosity flow curves were obtained using a rheometer (25ºC, 0-100s-1). Thermal analyses were performed on a differential scanning calorimeter, with heating rate of 10ºC/min (-100 to 100ºC). The water content and the pH of the honey samples varied from 17.2 to 27.9% and from 3.2 to 4.2, respectively, and, the aW of the samples varied from 0.57 to 0.74. Two samples were out of specification with respect to water content, according to Brazilian laws. In relation to rheology, all honey samples showed Newtonian behaviour with no thixotropy or dilatancy. The viscosity varied as an exponential function of the water content. The highest viscosity was obtained for the sample with lower values of water content and aW. Thermograms showed a glass transition (Tg) occurring between -52.4 and -42.6ºC, in the samples produced by Apis mellifera and -67.6 and -57.0ºC for the other samples. A linear relationship was obtained between Tg and water content. In conclusion, the honey viscosity depended on the water content of the product. The higher the water value and therefore the greater the aw, the lower viscosity and Tg of the samples.
Patricia Argemira Costa, Izabel Cristina Freitas Moraes, Ana Mônica Q.B. Bittante, Paulo José do Amaral Sobral, Catarina A. Gomide, Celso C. Carrer
01.12.2012.
Professional paper
Optimization of the Extraction of Antioxidants and Caffeine from Maté (Ilex paraguariensis) Leaves by Response Surface Methodology
Optimal conditions for the industrial extraction of total polyphenols from maté (Ilex paraguariensis) were determined using response surface methodology, with two independent variables: ethanol percentage of the extraction solution and liquid to solid ratio. Response variables were total polyphenol content, antioxidant capacity, concentration of total polyphenols and caffeine content. The optimal conditions found were a liquid to solid ratio from 8 - 9 w w-1 and ethanol percentage of the extraction solution from 30 -50 % w w-1. Under these conditions the main predicted values corresponding to leaf extracts were 40 μg chlorogenic acid equivalents mL-1 of original extract, 13 g chlorogenic acid equivalents per 100 g dry matter for total polyphenol content, 22 g Trolox equivalents and 15.5 g ascorbic acid equivalents per 100 g dry matter for antioxidant capacity. The total polyphenol content of twig extracts was 36% lower than that in the leaf extracts.
Vanessa Graciela Hartwig, Miguel Eduardo Schmalko, Stella Maris Alzamora, Luis Alberto Brumovsky
01.12.2012.
Professional paper
Effect of Biopreservatives on Storage Life of Papaya (Carica papaya L.)
In this experiment the effect on post-harvest preservation of papaya (Carica papaya L.) fruit coated with either Aloe gel (AG; 100%) or papaya leaf extract with Aloe gel (PLEAG; 1:1) was studied. To evaluate the role of coating on ripening behavior and quality of papaya the uncoated and coated fruits were stored and ripened at room temperature (25 °C-29 °C) and 82-84% relative humidity. Physico-chemical properties were analyzed at 4 day intervals during the storage period. The incidence of disease attack was also visually observed. The overall results showed the superiority of AG and PLEAG coating in lengthening the shelf-life of papaya fruit compared to controls which showed significant decay from 6th day onward and complete decay within 12 days of storage. The AG and PLEAG coated fruits maintained their shelf life for 12 days and decayed at 16th day. The coated fruits also maintained their color, flavor and firmness up to 12 days of storage. An increase in ascorbic acid content (120.2 mg/100 g) was also found in coated fruits in contrast to the control (59 mg/100 g). Only 27% disease incidence was observed in AG and 13% in PLEAG coated fruits as compared to control (100%) during the storage period. The results of this study show that both AG and PLEAG coatings have excellent potential to be used on fresh produce to maintain quality and extend shelf-life.
Fatema H. Brishti, Jawadul Misir, Ayesha Sarker
01.12.2012.
Professional paper
Effect of drying techniques on the retention of antioxidant activities of Saskatoon berries
The main objective of this research was to compare the retention of antioxidant activity and total anthocyanin content of Saskatoon berries dried by freeze drying, microwave-vacuum drying, thin layer hot air drying and vacuum drying. Antioxidant activity of berry samples was determined by DPPH radical scavenging and ABTS radical scavenging, and the pH differential method was used to determine total anthocyanin content of the berry samples. The results showed that the freeze dried Saskatoon berries exhibited the highest retention of anthocyanin and antioxidant activity among the dried samples, followed by microwave-vacuum dried berries, thin layer hot air dried berries and vacuum dried berries. There were significant differences between the berry samples at P<0.05. DPPH radical scavenging and ABTS radical scavenging were correlated linearly with an R2 value of 0.99 at P<0.05 showing their effectiveness for the determination of the antioxidant activity of the Saskatoon berries. However, the DPPH radical scavenging assay was more effective than the ABTS radical scavenging assay. The results also showed that antioxidant activity of the berries was highly correlated with the total anthocyanin content of the fruit. The reduction of anthocyanin in dried berry samples was linearly correlated with the reduction of DPPH radical scavenging with an R2 value of 0.97 at P<0.05 and, also, linearly correlated with the reduction of ABTS radical scavenging with an R2 value of 0.88 at P<0.05.
Pranabendu Mitra, Venkatesh Meda, Rick Green
01.12.2012.
Professional paper
Effect of structural modifications on the drying kinetics of foods: changes in volume, surface area and product shape
Macro and micro-structural changes take place during food dehydration. Macro-structural changes encompass modifications in shape, area and volume. Studies of such changes are important because dehydration kinetics (essential for calculating industrial dryers) may be highly influenced by changes in food shape and dimensions. The overall changes in volume, surface area (“shrinkage”) and shape (Heywood factor, with provides a close description of food shape) were determined experimentally, and the results were correlated with simple expressions. Hence, although dehydration kinetics can be modeled with simplified overall shrinkage expressions, the possibility of selecting a suitable geometry and predicting the characteristics dimensions will provide higher accuracy. An additional unresolved problem is the lack of a general model that predicts macro-structural changes for various foods and diverse geometries. In this work, based on experimental data of sweet and sour cherries, and rose hip fruits, a simplified general model to predict changes in volume and surface area are proposed. To estimate how the changes in characteristic dimensions affect the kinetic studies, experimental drying curves for the three fruits by means of a diffusional model considered the following variants for the characteristic dimensions: (i) The radius of the fresh food, assumed constant; (ii) The radius of the partially dehydrated product; (iii) The radius predicted by the correlation for structural changes, especially volume, obtained in this work and generalized for the three fruits, and (iv) to demonstrate the need to study the macro-structural changes for all dehydrated foods, also be present the case of a restructured food.
Antonio De Michelis, Carlos A. Márquez, Alejandra Mabellini, Elizabeth Ohaco, Sergio A. Giner
01.12.2012.
Professional paper
Effects of modified atmosphere, associated with masterpack transport packaging, and refrigerated storage time on the quality characteristics of pork loin cuts
The objective of this research was to study the effects of modified atmosphere, associated with masterpack transport packaging, and refrigerated storage time on the quality characteristics of pork loin cuts. Cuts of pork loin were packaged in trays, covered with poly(vinyl chloride) film. The trays were placed in a masterpack (MP), containing three gas compositions: A) 75% O2 : 25% CO2, B) 50% O2 : 50% CO2 or C) 100% CO2, and stored at 2 °C. Samples were taken after 1, 8, 15, and 22 days of storage, and evaluated for numerous shelf life traits. The development of Psychrotrophic aerobic bacteria and Pseudomonas spp. was found from the 15th day of storage. There was a significant treatment effect for some of the considered parameters, such as pH (P < 0.05) and color [L* (P < 0.07), a* (P < 0.07) and b* (P < 0.01)]. There was a significant interaction (P < 0.01) for the TBARS values. It can be concluded, from the microbiological point of view, that the use of modified atmospheres containing 25% to 100% CO2 promotes the conservation of meat for up to 15 days of storage under refrigeration. From the point of view of color, atmospheres containing 75% O2 : 25% CO2 and 50% O2 : 50% CO2 ensure the color of packaged pork meat when stored at 2 °C for up to 15 days. From the point of view of lipid oxidation, packages with 100% CO2 are recommended for storage periods of more than 15 days, whereas those with 75% O2 : 25% CO2 are recommended for storage periods of up to 8 days.
Alessandra F. Rosa, Mirele D. Poleti, Julio C.C. Balieiro, Marcelo C. César, Paulo J.A. Sobral
