Evaluation of molecular weight of Chitosan in thin-layer and spouted bed drying

Chitosan is chitin in deacetylated form and is the main constituent of crustacean exoskeletons. Commercially, chitosan is dried in tray driers, and during the operation, polymerization may occur as the chitosan is composed of carbohydrates. The aim of this work was to analyze chitosan in spouted bed and thin-layer drying, considering viscosity average molecular weight of the chitosan samples in the process. Results showed that spouted bed-dried chitosan presented a molecular weight value similar (160 kDa) to that of the raw one (150 kDa). However, when dried on tray dryers, the molecular weight was 300 kDa, indicating that molecule polymerization occurred.

Optimisation of Spirulina platensis convective drying: evaluation of phycocyanin loss and lipid oxidation

The aim of the study was the optimisation of Spirulina platensis drying on convective hot air through the response surface methodology. The responses were thiobarbituric acid (TBA) and phycocyanin loss percentage values in final product. Experiments were carried out in perforated tray drier with parallel air flow, and the wet samples thickness and drying air temperatures were in range of 3–7 mm and 50–70 °C, respectively. The statistical analysis showed significant effect (P < 0.05) for air temperature and samples thickness. In the best drying condition, 55 °C and 3.7 mm, presented the phycocyanin loss percentage and the TBA values of approximately 37% and 1.5 mgMDA kg−1, respectively. In this drying condition, the fatty acids composition of the microalgae Spirulina did not show significance difference (P > 0.05) in relation to fresh biomass. The lipid profile of dried product presented high percentage of polyunsaturated fatty acids (34.4%), especially the gamma-linolenic acid (20.6%).

Optimization of osmotic dehydration of papaya followed by air-drying

FERNANDES, Fabiano A. N. et al. Optimization of Osmotic Dehydration of Papaya of followed by air-drying. Food Research Internation, v. 39, p. 492-498, 2006.

Different aspects to consider during kiln drying of Vochysia guatemalensis Donn Sm. Wood (Cebo/Mayo)

Vochysia guatemalensis Donn Sm. wood is currently provided from plantations in several regions of Costa Rica. This wood presents several problems during the drying process such as high variability in the moisture content and high incidence of later defects. The objective of this study was to investigate the causes of this variation and defect developments. It was considered climate condition or precedence, grain pattern, drying schedule, boards position in relation to height and distance from to pith and heartwood presence.  The main factors affecting the moisture variability and drying defects were found to be: high initial moisture content variability in different parts of the tree, climate condition, and improper drying programs. Besides, there are recommendations to consider before starting the drying process. Thus a better wood quality in relation to moisture content variability and the presence of defects can be obtained after drying process.

Evaluation of thermo-physical properties and drying kinetics of carrots in a convective hot air drying system

This paper presents an experimental study on the evolution of carrot properties along convective drying by hot air at different temperatures (50ºC, 60ºC and 70ºC). The thermo-physical properties calculated were: specific heat, thermal conductivity, diffusivity, enthalpy, heat and mass transfer coefficients. Furthermore, the data of drying kinetics were treated and adjusted according to the three empirical models: Page, Henderson & Pabis and Logarithmic. The sorption isotherms were also determined and fitted using the GAB model. The results showed that, generally, the thermo-physical properties presented a decline during the drying process, and the decrease was faster for the temperature of 70ºC. It was possible to verify that the Page model presented the best prediction ability for the representation of kinetics of the drying process. The GAB model used to fit the sorption isotherms showed a good prediction capacity and, at a given water activity, despite some variations, the amount of water sorbed increased with the decrease of drying temperature.

Effect of pre-treatments and post-treatments on drying products

Freeze drying technology can give good quality attributes of vegetables and fruits in terms of color, nutrition, volume, rehydration kinetics, stability during storage, among others, when compared with solely air dried ones. However, published scientific works showed that treatments applied before and after air dehydration are effective in food attributes, improving its quality. Therefore, the hypothesis of the present thesis was focus in a vast research of scientific work that showed the possibility to apply a pre-treatment and a post-treatment to food products combined with conventional air drying aiming being close, or even better, to the quality that a freeze dried product can give. Such attributes are the enzymatic inactivation, stability during storage, drying and rehydration kinetics, color, nutrition, volume and texture/structure. With regard to pre-treatments, the ones studied along the present work were: water blanching, steam blanching, ultrasound, freezing, high pressure and osmotic dehydration. High electric pulsed field was also studied but the food attributes were not explained on detailed. Basically, water and steam blanching showed to be adequate to inactivate enzymes in order to prevent enzymatic browning and preserve the product quality during long storage periods. With regard to ultrasound pre-treatment the published results pointed that ultrasound is an effective pre-treatment to reduce further drying times, improve rehydration kinetics and color retention. On the other hand, studies showed that ultrasound allow sugars losses and, in some cases, can lead to cell disruption. For freezing pre-treatment an overall conclusion was difficult to draw for some food attributes, since, each fruit or vegetable is unique and freezing comprises a lot of variables. However, for the studied cases, freezing showed to be a pre-treatment able to enhance rehydration kinetics and color attributes. High pressure pre-treatment showed to inactivate enzymes improving storage stability of food and showed to have a positive performance in terms of rehydration. For other attributes, when high pressure technology was applied, the literature showed divergent results according with the crops used. Finally, osmotic dehydration has been widely used in food processing to incorporate a desired salt or sugar present in aqueous solution into the cellular structure of food matrix (improvement of nutrition attribute). Moreover, osmotic dehydration lead to shorter drying times and the impregnation of solutes during osmose allow cellular strengthens of food. In case of post-treatments, puffing and a new technology denominated as instant controlled pressure drop (DIC) were reported in the literature as treatments able to improve diverse Abstract Effect of Pre-treatments and Post-treatments on Drying Products x food attributes. Basically, both technologies are similar where the product is submitted to a high pressure step and the process can make use of different heating mediums such as CO2, steam, air and N2. However, there exist a significant difference related with the final stage of both which can comprise the quality of the final product. On the other hand, puffing and DIC are used to expand cellular tissues improving the volume of food samples, helping in rehydration kinetics as posterior procedure, among others. The effectiveness of such pre and/or post-treatments is dependent on the state of the vegetables and fruits used which are also dependent of its cellular structure, variety, origin, state (fresh, ripe, raw), harvesting conditions, etc. In conclusion, as it was seen in the open literature, the application of pre-treatments and post-treatments coupled with a conventional air dehydration aim to give dehydrated food products with similar quality of freeze dried ones. Along the present Master thesis the experimental data was removed due to confidential reasons of the company Unilever R&D Vlaardingen

Application of survival analysis to determine the persimmon cv. 'Rama-forte' sensory shelf-life.

2014

Effect of drying on the physical, chemical and sensorial properties of kiwi

Kiwi fruit is a highly nutritional fruit due to the high level of vitamin C and its strong antioxidant capacity due to a wide number of phytonutrients including carotenoids, lutein, phenolics, flavonoids and chlorophyll [1]. Drying consists of a complex process in which simultaneous heat and mass transfer occur. Several alterations occur during the drying of foods at many levels (physical, chemical, nutritional or sensorial) which are influenced by a number of factors, including processing conditions [2]. Temperature is particularly important because of the effects it produces at the chemical and also at the physical level, particularly colour and texture [3]. In the present work were evaluated the changes in sliced kiwi when exposed to air drying at different temperatures (50, 60, 70, 80 ºC), namely in terms of some chemical properties like ascorbic acid or phenolic compounds, physical characteristics like colour and texture and also at the sensorial level. All experiments followed standard established procedures and several replicates were done to assess each property. The results obtained indicated that moisture was reduced with drying by 74 to 87%, depending on the temperature. Also ascorbic acid decreased with drying, being 7% for 50 ºC and increasing up to 28% for the highest temperature (80 ºC). The phenolic compounds and antioxidant activity were also very much affected by the drying temperature. The water activity of the dried samples varied from 0.658 to 0.753, being compatible with a good preservation. Regarding colour, the total colour difference between the dried samples and the fresh sample was found to vary in the range 9.45 – 17.17. The textural parameters were also much affected by drying, namely hardness which decreased by 45 to 72 %, and all other parameters increased: cohesiveness (approximately doubled), springiness (increased 2 to 3 times) and chewiness which increased up to 2.5 times that off the fresh sample. Adhesiveness, which was observed for the fresh samples (-4.02 N.s) disappeared in all the dried samples. The sensorial analysis made to the dried samples allowed establishing the sensorial profiles as shown in Figure 1.

Experimental and modeling studies of forced convection storage and drying systems for sweet potatoes

Sweet potato is an important strategic agricultural crop grown in many countries around the world. The roots and aerial vine components of the crop are used for both human consumption and, to some extent as a cheap source of animal feed. In spite of its economic value and growing contribution to health and nutrition, harvested sweet potato roots and aerial vine components has limited shelf-life and is easily susceptible to post-harvest losses. Although post-harvest losses of both sweet potato roots and aerial vine components is significant, there is no information available that will support the design and development of appropriate storage and preservation systems. In this context, the present study was initiated to improve scientific knowledge about sweet potato post-harvest handling. Additionally, the study also seeks to develop a PV ventilated mud storehouse for storage of sweet potato roots under tropical conditions. In study one, airflow resistance of sweet potato aerial vine components was investigated. The influence of different operating parameters such as airflow rate, moisture content and bulk depth at different levels on airflow resistance was analyzed. All the operating parameters were observed to have significant (P < 0.01) effect on airflow resistance. Prediction models were developed and were found to adequately describe the experimental pressure drop data. In study two, the resistance of airflow through unwashed and clean sweet potato roots was investigated. The effect of sweet potato roots shape factor, surface roughness, orientation to airflow, and presence of soil fraction on airflow resistance was also assessed. The pressure drop through unwashed and clean sweet potato roots was observed to increase with higher airflow, bed depth, root grade composition, and presence of soil fraction. The physical properties of the roots were incorporated into a modified Ergun model and compared with a modified Shedd’s model. The modified Ergun model provided the best fit to the experimental data when compared with the modified Shedd’s model. In study three, the effect of sweet potato root size (medium and large), different air velocity and temperature on the cooling/or heating rate and time of individual sweet potato roots were investigated. Also, a simulation model which is based on the fundamental solution of the transient equations was proposed for estimating the cooling and heating time at the centre of sweet potato roots. The results showed that increasing air velocity during cooling and heating significantly (P < 0.05) affects the cooling and heating times. Furthermore, the cooling and heating times were significantly different (P < 0.05) among medium and large size sweet potato roots. Comparison of the simulation results with experimental data confirmed that the transient simulation model can be used to accurately estimate the cooling and heating times of whole sweet potato roots under forced convection conditions. In study four, the performance of charcoal evaporative cooling pad configurations for integration into sweet potato roots storage systems was investigated. The experiments were carried out at different levels of air velocity, water flow rates, and three pad configurations: single layer pad (SLP), double layers pad (DLP) and triple layers pad (TLP) made out of small and large size charcoal particles. The results showed that higher air velocity has tremendous effect on pressure drop. Increasing the water flow rate above the range tested had no practical benefits in terms of cooling. It was observed that DLP and TLD configurations with larger wet surface area for both types of pads provided high cooling efficiencies. In study five, CFD technique in the ANSYS Fluent software was used to simulate airflow distribution in a low-cost mud storehouse. By theoretically investigating different geometries of air inlet, plenum chamber, and outlet as well as its placement using ANSYS Fluent software, an acceptable geometry with uniform air distribution was selected and constructed. Experimental measurements validated the selected design. In study six, the performance of the developed PV ventilated system was investigated. Field measurements showed satisfactory results of the directly coupled PV ventilated system. Furthermore, the option of integrating a low-cost evaporative cooling system into the mud storage structure was also investigated. The results showed a reduction of ambient temperature inside the mud storehouse while relative humidity was enhanced. The ability of the developed storage system to provide and maintain airflow, temperature and relative humidity which are the key parameters for shelf-life extension of sweet potato roots highlight its ability to reduce post-harvest losses at the farmer level, particularly under tropical climate conditions.

Changes in enzymatic activity, accumulation of proteins and softening of persimmon (Diospyros kaki Thunb.) flesh as a function of pre-cooling acclimatization.

One of the major causes of ?Fuyu? persimmon loss after cold storage (CS) is the breakdown of its flesh, which results in the production of a translucent fruit (a water-soaked fruit). It is believed that the cause of this disturbance is linked to disorganization of the cytoskelet and endomembrane system, which changes the synthesis and transport of proteins and metabolites, resulting in incomplete ripening. To test this hypothesis, ?Fuyu? persimmon was subjected to three different postharvest treatments (T): Control ? harvested and kept at 23±3 ◦C and relative humidity (RH) of 85±5% (room temperature, RT) for 12 days, T1 ? harvested and kept under cold storage (CS) (1±1 ◦C and RH of 85±5%) for 30 days followed by RT storage for 2 days, T2 ? kept under RT for 2 days (acclimatization) followed by CS for 30 days. Control and T2 resulted in fruit with decreased flesh firmness (FF), and increased soluble solids (SS) and ascorbic acid (AA) contents. In these fruit the activity of endo-1,4-ß-glucanase (endo-1,4-ß-gluc), pectin methylesterase (PME), polygalacturonase (PG) and ß-galactosidase (ß-gal) increased. T1 resulted in translucent fruit with decreased FF, without any enzymatic activity changes, probably due to the physical disruption of the cytoskeleton. Further, there was an increased content of proteins corresponding to expansins in fruit kept under Control and T2 conditions, which suggests that these conditions do contribute to the synthesis and/or transport of proteins involved in the process of solubilization of the cell wall. In these fruit, there was also a major accumulation of gene transcripts corresponding to heat shock proteins (HSPs) of organelles related to endomembrane, which suggests participation of these genes in the prevention of damage caused by cold conditions. These data proved the hypotheses that acclimatization contributes to the expression of HSPs, and synthesis and transportat of proteins involved in the solubilization of the cell wall. The expression of these genes results in the normal ripening of the persimmon, as confirmed by the evolution of ethylene production.

Mealybugs (Hemiptera: Pseudococcidae) associated with persimmon Diospyros kaki L. (Ebenaceae) in Southern Brazil.

Temperate fruit production is an important economic activity in Southern Brazil. In this region, persimmon Diospyros kaki L. (Ebenaceae) is grown in small farms for domestic consumption and internal market. Mealybugs are o*en found in at least 50% of the orchards causing damages on fruits due to the honeydew secretion. However, there is a lack of informatin about species composition damaging orchards in Southern Brazil. In this work, we present a survey of mealybugs associated with persimmon trees in the Serra Gaúcha Region, Rio Grande do Sul, Brazil.

Drying of rye (Lolium miltiflorum l.) in fixed bed with parallel air flow.

This work aimed to study the drying of ryegrass seeds (Lolium multiflorum L.) in fixed bed dryer with parallel air flow.

Increasing the Physical Quality of Instant Yogurt by Spray Drying with Instant Additive

This research was carried out to compare the effects of soy lecithin and yolk as instant additive, to know the effects of instant additive level and their interaction on physical quality of instant yogurt (rehydration rate, solubility and viscosity).  The data were analyzed by statistical analysis based on Completely Randomized Block Design (CRBD) with factorial pattern (2x3) using one control treatment (without instant additive), if the result were significant, then continued by Duncan’s New Multiple Range test (DMRT).  The first factor was variety of instant additive (soy lecithin, yolk), whereas the second factor was concentration of instant additive (0.5, 1.0 and 1.5% v/v).  The result of this research showed that variety of instant additive has no significant effect on viscosity, but it has significant effect  (P<0.05) on rehydration rate and solubility.  The second factor has significant effect (P<0.05) on solubility, but has no significantly effect on rehydration rate and viscosity.  Interaction of them only occurred on solubility of instant yogurt.  The result of DMRT showed that the increasing physical quality of instant yogurt occurred on the 0.5% concentration. It was compared with control treatment.  Increasing concentration has no effect on rehydration rate, solubility or viscosity, except on solubility.  The solubility decreased at level of instant additive 1.5%.  The conclusions of this research were soy lecithin and yolk had different ability to increase solubility and rehydration rate but gave similar effect on viscosity.  Application of soy lecithin or yolk as instant additive up to 0.5% would increase physical quality of instant yogurt (rehydration rate, viscosity and solubility).  As compare to soy lecithin, yolk has better performance in increasing and making stable solubility of instant yogurt. (Animal Production 6(1): 1-8 (2004) Key Words:  Instant Yogurt, Soy Lecithin, Yolk, Physical Quality

Polyurethane (PU) scaffolds prepared by solvent casting/particulate leaching (SCPL) combined with centrifugation

This article reports an enhanced solvent casting/particulate (salt) leaching (SCPL) method developed for preparing three-dimensional porous polyurethane (PU) scaffolds for cardiac tissue engineering. The solvent for the preparation of the PU scaffolds was a mixture of dimethylformamide (DFM) and tetrahydrofuran (THF). The enhanced method involved the combination of a conventional SCPL method and a step of centrifugation, with the centrifugation being employed to improve the pore uniformity and the pore interconnectivity of scaffolds. Highly porous three-dimensional scaffolds with a well interconnected porous structure could be achieved at the polymer solution concentration of up to 20% by air or vacuum drying to remove the solvent. When the salt particle sizes of 212-295, 295-425, or 425-531 µm and a 15% w/v polymer solution concentration were used, the porosity of the scaffolds was between 83-92% and the compression moduli of the scaffolds were between 13 kPa and 28 kPa. Type I collagen acidic solution was introduced into the pores of a PU scaffold to coat the collagen onto the pore walls throughout the whole PU scaffold. The human aortic endothelial cells (HAECs) cultured in the collagen-coated PU scaffold for 2 weeks were observed by scanning electron microscopy (SEM). It was shown that the enhanced SCPL method and the collagen coating resulted in a spatially uniform distribution of cells throughout the collagen-coated PU scaffold.