Conrad O. Perera

DESORPTION ISOTHERM AND HEAT PUMP DRYING KINETICS OF PEAS

Abstract Moisture desorption isotherms and thin layer drying kinetices of peas in a laboratory pilot heat pump dryer were measured and modeled. A mesh bottom tray was used and air flow was parallel to the two faces of the thin layer. Air drying temperature, and relative humidity were varied from 25 to 65 °C and 0.20 to 0.60, respectively. The air velocity was 1.5ms−1. A two component exponential model was used to represent the heat pump drying curves. The model parameters were correlated with the temperature and relative humidity. The two component model and correlations for the parameters developed can be used to predict the moisture content of peas during heat pump air drying.

Properties of Bread Dough with Added Fiber Polysaccharides and Phenolic Antioxidants: A Review

During breadmaking, different ingredients are used to ensure the development of a continuous protein network that is essential for bread quality. Interests in incorporating bioactive ingredients such as dietary fiber (DF) and phenolic antioxidants into popular foods such as bread have grown rapidly, due to the increased consumer health awareness. The added bioactive ingredients may or may not promote the protein cross-links. Appropriate cross-links among wheat proteins, fiber polysaccharides, and phenolic antioxidants could be the most critical factor for bread dough enhanced with DF and phenolic antioxidants. Such cross-links may influence the structure and properties of a bread system during baking. This article presents a brief overview of our current knowledge of the fate of the key components (wheat proteins, fibers, and phenolic antioxidants) and how they might interact during bread dough development and baking.

Selected Quality Attributes of Dried Foods

Abstract: Major quality parameters associated with dried food products are the color, visual appeal, shape of product, flavor, microbial load, retention of nutrients, porosity bulk density, texture, rehydration properties, water activity and chemical stability, preservatives, and freedom from pests, insects and other contaminants, as well as freedom from taints and off-odors. These parameters need to comply with the specifications of customers and regulations of different importing countries and often can adversely affect the acceptability of dried products. Therefore, quality of dried food products depends on many factors, such as raw materials, processing environment, packaging, microbial stability, use of additives, and temperature of storage. This review highlights selected quality attributes of dried food products and discusses ways of optimizing them.

State diagram of apple slices : glass transition and freezing curves

Abstract The state diagram of apple flesh was developed by measuring and modeling its freezing points and glass transition temperatures. The freezing curve and glass transition lines were developed using Clausias–Clapeyron and Gordon–Taylor models, respectively. The state diagram of apple pieces developed in this work can be used in determining the stability during frozen storage and in dried conditions as well as in designing drying and freezing processes.

Heat pump dehumidifier drying of food

Although heat pumps have been used extensively in industry for many years, their use for drying, especially foods, has been limited. This article reviews the potential of heat pump dehumidifier (HPD) dryers for use in food drying. HPD dryers offer several advantages over conventional hot-air dryers for the drying of food products, including higher energy efficiency, better product quality, and the ability to operate independently of outside ambient weather conditions. In addition, this technology is environmentally friendly in that gases and fumes are not given off into the atmosphere. The condensate can be recovered and disposed of in an appropriate manner, and there is also the potential to recover valuable volatiles from the condensate.

Functional Properties of Carotenoids in Human Health

Carotenoids are compounds of great dietery importance. Recent interest in carotenoids has been stimulated by epidemiological studies that strongly suggest that consumption of carotenoid-rich foods reduces the incidence of several diseases such as cancers, cardiovascular diseases, age-related macular degeneration, cataracts, diseases related to low immune function, and other degenerative diseases. Health benefits of carotenoids are derived from the fruits and vegetables in the diet, particularly from cooked products containing oil, or from supplements of their extracts, such as tomato sauce, dried tomatoes, or those suspended in oil. This article provides a brief overview of the chemistry of carotenoids—their absorption, transport, bioavailability, metabolism, and their action as antioxidants, and in the prevention of a number of common diseases.

Drying of Guava and Papaya: Impact of Different Drying Methods

Heat pump dryers (HPD) are known as high-energy-efficiency devices with low economic cost. As it is usually a closed system, the drying media can be substituted by inert gases. In this study, the effect of nitrogen and carbon dioxide on guava and papaya were investigated. Both drying kinetics and quality of these dried fruits resulting from the two methods were compared with normal air HPD, vacuum dryer, and freeze dryer. When using CO2, the effective diffusivity during the drying process was 44% higher in guava and 16.34% higher in papaya. There was less browning, faster rehydration, and more vitamin C retention in the final products. All these reveal the great potential of modified atmosphere heat pump dryer in the food drying industry.

Density, shrinkage and porosity of calamari mantle meat during air drying in a cabinet dryer as a function of water content

Abstract The particle density of calamari mantle meat powder decreased with increasing water content and apparent density gave a peak at low water content, then decreased with increasing water content. The shrinkage and porosity were derived from the experimental density data and were correlated empirically. The empirical models were used to predict the density data. An attempt was made to apply the theoretical model proposed by Rahman (1991, Ph.D. Thesis, University of New South Wales, Australia) based on conservation of mass and volume, and modified to include excess volume and air pore formation. The uncertainty in the true density measurement, which is a common difficulty in this area, has made it impossible to predict accurately the excess volume, thus limiting Rahmans model.

Comparison of the Retention of 6-Gingerol in Drying of Ginger Under Modified Atmosphere Heat Pump Drying and other Drying Methods

A heat pump dryer using normal air, nitrogen, and carbon dioxide was selected to dry sliced West Indian ginger (Zingiber officinale Roscoe) rhizome (3 mm in thickness). The drying characteristics were compared with each other and inert gas heat pump drying showed an improved effective diffusivity. Quantities of the main pungent principle (6-gingerol) of ginger, extracted from these dried samples, were determined by high-pressure liquid chromatography (HPLC). The evaluation included dried samples obtained by heat pump, modified atmosphere heat pump, freeze drying, and vacuum drying. Retention of 6-gingerol increased in the order of normal air drying, freeze drying, nitrogen drying, carbon dioxide drying, and vacuum drying. From this point of view, inert gas also showed a better retention of flavor compared to most other types of drying.

Evaluation of gallic acid loaded zein sub-micron electrospun fibre mats as novel active packaging materials

The applicability of gallic acid loaded zein (Ze-GA) electrospun fibre mats towards potential active food packaging material was evaluated. The surface chemistry of the electrospun fibre mats was determined using X-ray photon spectroscopy (XPS). The electrospun fibre mats showed low water activity and whitish colour. Thermogravimetric analysis (TGA) and Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy revealed the stability of the fibre mats over time. The Ze-GA fibre mats displayed similar rapid release profiles, with Ze-GA 20% exhibiting the fastest release rate in water as compared to the others. Gallic acid diffuses from the electrospun fibres in a Fickian diffusion manner and the data obtained exhibited a better fit to Higuchi model. L929 fibroblast cells were cultured on the electrospun fibres to demonstrate the absence of cytotoxicity. Overall, the Ze-GA fibre mats demonstrated antibacterial activity and properties consistent with those considered desirable for active packaging material in the food industry.