Kehinde A. Taiwo

Use of pulsed electric field pre-treatment to improve dehydration characteristics of plant based foods

Abstract Conventional dehydration of fruits and vegetables affects their physical and biochemical status leading to shrinkage, change of colour, texture and taste. Alteration of the physical properties of foods with minimal influence on the quality could be a means of reducing drying time, minimising quality degradation and saving energy. Increasing consumer markets for minimally processed fruits and vegetables have prompted researchers to study combined methods as preservation techniques. Pulsed electric field is one of the more promising non- thermal processing method inducing membrane permeabilisation within a very short time (μs to ms range) leaving the product matrix largely unchanged while positively affecting mass transfer in subsequent processing of foods. Rapid and accurate on-line determination of the state of cell membrane systems is important in optimising various processes (i.e. minimizing cell damage in minimal processes, monitoring disruption for mass transfer purposes and inducing biosynthetic stress/wound reactions/responses). This paper reviews recent work on the use of pulsed electric fields as an upstream process in dehydration and rehydration of plant based foods. An effective and simple method for quantifying extent of membrane permeabilization is also discussed and suggestions for future work are highlighted.

Comparison of pretreatment methods on water and solid diffusion kinetics of osmotically dehydrated mangos

Abstract This study compared mass transfer during osmotic dehydration (OD), as well as some quality indices, of untreated mango samples to those pretreated by applying high intensity electric field pulses (HELPs), high pressure (HP) or supercritical carbon dioxide having the same initial cell disintegration index ( Z p ) in the range 0.50–0.58. HELP and HP pretreated samples had a higher water loss (WL) and higher solid gain (Sg) than the untreated samples. Applying supercritical carbon dioxide did not improve water loss but facilitated higher sugar gain (8–42%) than in the other pretreated samples. HP and supercritical carbon dioxide pretreatments increased the red intensity ( a values) of the mangos. The breaking force of HELP and HP pretreated samples increased with OD time.

Comparative evaluation of the effects of pulsed electric field and freezing on cell membrane permeabilisation and mass transfer during dehydration of red bell peppers

Abstract The extent of cell membrane permeabilisation due to high intensity electric field pulses (HELP) varying number of pulses (1–50) using electric field of 2 kV/cm, 400 μs pulse duration and freezing on mass transfer and vitamin C content during osmotic (50° Brix sucrose at 40 °C) and convective air (60 °C, 1 m/s for 5 h) dehydration of red bell peppers was studied. Total pore area due to HELP increased with number of pulses while freezing resulted in total pore area of almost 6 times as greater as the highest value from the HELP process. Higher water loss was observed for all HELP treated than for prefrozen samples while slow freezing provided samples with the highest solids uptake. The correlation coefficient (R2) of linear regression between water loss and solids gain estimated from either total solids or soluble solids measurement ranged from 0.954 to 0.998 suggesting the possibility of using the soluble solids method in evaluating mass transfer kinetics during osmotic dehydration process. Drying rate during convective air-drying was more enhanced by HELP than by freezing. Electrical conductivity of the osmotic solution increased with the degree of permeabilisation to a given medium value after which no further increase in the release of the intracellular ions was observed. Minimal vitamin C depletion was observed immediately after HELP treatment. The order of magnitude of vitamin C retention was untreated>frozen>HELP pretreated samples with 1 pulse>5 pulses>50 pulses>10 pulses>20 pulses after osmotic dehydration. The reduction in vitamin C content of HELP treated samples after convective drying ranged from approximately 11 to 24% while freezing resulted in approximately 24% decrease compared to the untreated samples.

The potential of cowpea as human food in Nigeria

Abstract Nigeria is a major producer of cowpea but the various methods of storing and preserving the crop locally are grossly inadequate. However, with the development of higher yielding varieties the need to consider other means of preserving cowpea has become urgent. This paper examines some of the factors influencing the production, preservation and utilisation of cowpea within Nigeria. The paper discusses the processing of cowpea as an alternative form of preservation. The utilisation of cowpea in the production of bean flour and as a canned product in tomato sauce are discussed with their relative economic advantages. The production of cowpea flour with good functional and reconstitutional properties has a potentially large market as it can be readily incorporated in various recipes. The production of commercially sterile cowpea in tomato sauce as a local substitute to imported baked beans will not only save the country some foreign exchange earnings, but will also lead to industrial growth, thereby generating employment for the populace.

Utilization Potentials of Cassava in Nigeria: The Domestic and Industrial Products

Cassava (Manihot esculenta) is an important food crop in the tropics—a major carbohydrate staple consumed in various forms by humans. Furthermore, its usage as a source of ethanol for fuel, energy in animal feed, and starch for industry is increasing. Given that cassava represents a valuable subsistence and cash crop in many countries, its domestic and industrial potential needs to be fully exploited. Processing of cassava reduces the moisture content and converts it into a more durable and stable product. Women traditionally process cassava, although it could be processed at the small, medium, or industrial scale. This article discusses the major Nigerian domestic products as well as the potential industrial products of cassava that are yet to be produced locally and the machines used in their production. Although improved technology is one of the keys to increasing the productivity of micro-enterprises and generating broad-based, sustainable economic growth, the extent to which a given technology is acceptable to a given culture may depend on a number of considerations beyond the mechanical efficiency of the device. These topics are discussed and recommendations are suggested to encourage the establishment of more cassava based industries.

The effects of soaking and cooking time on the cooking properties of two cowpea varieties

The effects of soaking and cooking time on water absorption capacity, cookability, percent split, and texture of two varieties of cowpea, IITA-2246 and IFE-BPC, were investigated. Soaking prior to cooking had an effect only on the cookability, while the amount of water absorbed and the penetration depth (a measure of texture) of a penetrometer head in the seeds increased with cooking time. The properties were found to differ notably for the two varieties with IITA-2246 having a softer texture than IFE-BPC. Splitting in cooked beans increased with cooking time with maximum of 92% split in IITA-2246 and 63% split for IFE-BPC. Higher temperature soaking reduced the cooking time of both varieties.

Regression relationships for the soaking and cooking properties of two cowpea varieties

Abstract Water absorption and penetration depth (a measure of texture) of two cowpea varieties as influenced by varying soaking time (0.15–6 h) and soaking temperature (28–75 °C) were determined. The effects of different soaking treatments prior to cooking and cooking time on percent split, drained weight and the penetration depth of the cooked cowpeas were also investigated. The aim of the study is to establish mathematical relations between the product characteristics by regression statistics. Water absorption correlated positively with soaking time but the goodness of fit was temperature and variety dependent. Poor correlation coefficients were obtained when the penetration depth of the seeds was expressed as a sole (linear) function of soaking time or amount of water absorbed. However, equations involving both variables described the penetration depth of soaked cowpeas better. Cooking time correlated very well with drained weight (0.883 ≤ r ≤ 0.979), percent split (0.797 ≤ r ≤ 0.962) and penetration depth of cooked seeds (0.895 ≤ r ≤ 0.982). Equations involving drained weight and cooking time as variables were developed to predict the penetration depth of cooked cowpeas. The degree of fit increased with the inclusion of the product or higher order terms (0.841 ≤ r ≤ 0.996).

Technological assessment of palm oil production in Osun and Ondo states of Nigeria

Abstract The potential economic returns from the oil palm are high if processed with efficient technologies. This study was undertaken to evaluate the technologies in use for the production of palm oil from a gender perspective. A survey was conducted in Osun and Ondo States of Nigeria using a structured questionnaire and the participatory learning approach. A total of 28 palm fruit processing centres were surveyed. The various technologies available in the field for each unit operation were evaluated using certain criteria. Palm oil production is dominated by female processors and male assistance is sought in operating the machines and in carrying out strenuous tasks. Only two of the unit operations (digestion and extraction) have been partially mechanised while the other processes (quartering, stripping, sterilising, and clarifying) are performed manually. None of the machine operators interviewed had any formal training in machine operation and maintenance but they perform these tasks after learning by observation. The result of this study indicates an urgent need for establishing a training program both for machine operators and the maintenance personnel. There is no organised drainage system in the palm oil processing centres except at the industrial mills. Waste water is disposed of in surrounding bushes. The traditional technologies exposed the processors to the vagaries of the weather and other operational hazards. The technology profile proposed for the various unit operations is that of modest but accessible changes that work within the existing system and could be adopted by large numbers of women.

Thermal properties of ground and hydrated cowpea

Abstract The effects of temperature (50–80 °C) and moisture content 9.1–41.2% (wet basis) on the specific heat of ground and hydrated cowpea were investigated using the method of mixtures. For most of the samples, the specific heat was highest either at 60 °C or 28.6% moisture content. Further increase beyond these levels resulted in a decrease in the specific heat. Density was determined at room temperature. An initial decrease was observed in density of the samples as moisture level increased from 9.1%, but above 23.1% moisture content, the density increased with higher moisture levels. Thermal conductivity was determined by the line probe method. The thermal conductivity of ground and hydrated cowpea was dependent on moisture content and bulk density but independent of temperature.

A STUDY ON THE NIGERIAN FOOD INDUSTRY AND THE IMPACT OF TECHNOLOGICAL CHANGES ON THE SMALL-SCALE FOOD ENTERPRISES

Industrial processing of foods assists the nation to maintain a steady supply of food products. This study assessed some factors influencing the growth of the Nigerian food industry with the view to identify some technological changes within the small-scale food enterprises and their impact in the last ten years. Information on the Nigerian food industry was compiled from a secondary source while a survey of small-scale food enterprises was conducted in SouthWest Nigeria using a structured questionnaire and interviews. Results showed that the number of food manufacturing companies (FMCs) increased over the years with the largest number of FMCs established in the 1980s. The range of products produced is still small, with several FMCs producing similar products. More than 50% of the FMCs in the country are located in the SouthWest, with Lagos State as the major host. About 91% of the FMCs are listed as private and 7.3% are publicly quoted. Indigenous entrepreneurs wholly own 56.9% of the FMCs. Percent local sourcing is high in the FMCs. Areas of technological changes include expanded capacity utilization, expansion of production lines and expanded market shares, which arose as a result of the active involvement of management in the production process, acquisition of new packaging systems, and participation of the work force in process improvement. The study identified the need to standardize locally fabricated equipment to facilitate ready production of spare parts. Recommendations were made on how to increase the financial base of the small-scale enterprises.