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Moisture adsorption and desorption isotherms of gelatin extracted from whitefish skin powder (FSGP) at different temperatures across a wide range of water activity were determined along with their thermodynamic properties. Nine mathematical models were utilized for fitting the experimental data and simulating the adsorption and desorption behavior. The thermodynamic properties were determined and fitted to the experimental data. The results showed that Peleg and GAB models were the best fit for FSGP. The energies involved in the adsorption and desorption process of FSGP indicated a stronger dependence on equilibrium moisture content (Xe). When Xe decreased, there was a consistent trend of increasing thermodynamic properties. Both the moisture adsorption and desorption behaviors of FSGP were, therefore, non-spontaneous processes. Linear correlations between the changes in enthalpy and entropy for adsorption and desorption were observed, indicating the presence of enthalpy–entropy compensation for FSGP. For preserving FSGP quality, it should be stored with Xw ≤ 8 (gw/gdm, d.b.) at temperatures below 53 °C and an RH of 50% to avoid it becoming rubbery. These findings are crucial for providing insight into the optimal drying and storage conditions. [ABSTRACT FROM AUTHOR]

Huge quantities of agricultural waste are available annually in Saudi Arabia, which are not well exploited, leading to large environmental pollution and health problems. The use of different proportions of tomato waste compost (TWC) mixed with commercial peat-moss as a natural, economical, cheap and environmentally friendly fertilizer for fertilizing vegetables is very important, therefore, this study is concerned with investigating and evaluating the dry matter content (DM) and the accumulated heavy metal contents (HMs) in the root and leaf seedlings tissues of cucumber and summer squash plants as a result of using this fertilizer. Five ratios of mixtures (vermiculite: peat moss: TWC by weight) used in the experiment, and the TWC in the mixture represents 0, 5, 10, 15 and 20% (by wieght). The results indicated that, the DM contents in the root and leaf tissues were relatively close between cucumber and summer squash seedlings. However, they were higher in the root than in leaf tissues, particularly under 20% TWC. A TWC application ratio of 20% reduced concentrations of the most HMs in the two vegetable species seedlings due to high EC and pH levels. The amounts of HMs in vegetable species were not high, which proves the that transfer of HMs from the TWC substrate to the seedlings is determined chiefly by metal bioavailability and by a vegetable species. DM, mineral and nutritional quality of vegetable seedlings showed that substrates containing 5% and 10% TWC appeared to be the most suitable growing medium for economic vegetable seedlings; and it is recommended for use in the nursery production. Implications: The idea of this research revolves around the use of different proportions of tomato waste compost in fertilizing cucumber and summer squash seedlings and investigate the effect of this compost on dry matter (DM) and heavy metal (HMs) contents in the root and leaf tissues of the seedlings, and fruit quality of cucumber and summer squash plants. [ABSTRACT FROM AUTHOR]

Peat-moss (Sphagnum spp.), is currently an expensive material and a nonrenewable resource with variable properties. Therefore, its use should be gradually reduced. Hence, there are numerous attempts aiming to reduce the use of peat-moss as a bulk substrate and to search for high-quality, locally available and low-cost alternatives to peat-moss. Therefore, the main objective of this research is to investigate the effect of partial replacing of peat-moss with tomato waste compost (TWC) on plant growth, productivity, fruit quality, and morphological features of two types of economic cucurbits species under greenhouse conditions. The plants were planted into pots containing different proportions of TWC (0%, 5%, 10%, 15%, 20% and 30%) with peat-moss, sand and clay as growing substrates. The results indicated that the plant height and the leaves number of both plants were significantly influenced by different substrate treatments. TWC ratios of 15% and 20% increased the amount of cucumber and summer squash fruit yield more than the commercial peat media but they had insignificant differences. Also, they were significantly improved fruit quality characteristics, particularly total soluble solid (TSS) and titratable acidity (TA) of crop fruits more than commercial peat-moss treatment. Implications: Because of the high price of peat-moss and that it is a non-renewable material, farmers resorted to using other alternatives, including green residue compost. Thus, the aim of this work is to reduce the use of peat-moss by replacing it with the use of lokw percentages of TWC. When tomato plant residues return to the soil by converting them into compost, this is a valuable agricultural practice to improve soil fertility and increase the organic matter of the soil as well as increase the source of nitrogen (N) that supports the growth of beneficial microorganisms. [ABSTRACT FROM AUTHOR]

The efficiency of the composting process for tomato residues and chicken manure was estimated after monitoring of the rotary composting system. Physicochemical parameters and Compost Quality Index were evaluated. The tomato residues (leaves, stems, and some green and damaged fruits) were collected, cut into small pieces, moistened approximately (60–65%), and mixed with 20% chicken manure then distributed into three rotary drum bioreactors. The obtained results showed that, the temperature above 50°C was maintained for more than two days. Carbon: nitrogen (C:N) ratio was reduced from 30:1 to 19.13:1. The pH value ranged between 7 and 8.80 during the composting process, while the electrical conductivity (EC) ranged between 2.67 to 4.53 dS/m. Both compost quality parameters (Dewar and germination index) and (Solvita-CO2 and Solvita-NH3) indicated that, the final compost is stable and mature. Implications: The idea of this research revolves around assessing the maturity and stability of the compost resulting from mixing tomato residues with chicken manure, using a rotary drum bioreactor which is characterized by reducing the time of the active phase to several hours or days instead of weeks or months. Several tests related to the maturity and stability of mixture have been used to judge its quality. Also, many parameters related to this topic were monitored and discussed with many previous researches to determine the importance of benefiting from mixing the different wastes together and obtaining a good fertilizer ready for application as an agricultural substrate or a soil conditioner. [ABSTRACT FROM AUTHOR]

Plant residues consist of biodegradable organic materials and minerals that are well suited for compost production. The main prerequisite for compost to be safely applied into the soil is a high degree of stability and maturity, and the physical manifestation of this includes high stable organic matter content, and a lack of phytotoxic compounds. Tomato plant residues enriched with 20% chicken manure were composted in three rotary drum bioreactors to produce tomato waste compost (TWC) as a final product. Several physio-chemical stability and maturity parameters were assessed for the TWC. In addition, CIELAB color space parameters were used to ensure the stability and maturity of TWC as an alternative, fast, and low-cost technique for evaluating stability and maturity indices of compost. The results indicated stabilization of organic matter transformations during the composting process to create TWC. During active and curing phases of composting, results of the color parameters were in accordance with the measured physio-chemical maturity parameters; and the changes in TWC colors during active and curing phases of composting indicated that the final compost product was stable, mature, and that color analysis provided a low-cost alternative analytical approach for assessing the suitability of compost as a soil conditioner. [ABSTRACT FROM AUTHOR]

Energy produced from plant residue composting has stimulated great interest in heat recovery and utilization. Composting is an exothermic process often controlled through temperature measurements. However, energy analysis of the overall composting system, especially the rotary bioreactors, is generally not well known and very limited. This study presents detailed energy analysis in a laboratory-scale, batch-operated, rotary bioreactor used for composting tomato plant residues. The bioreactor was considered as a thermodynamic system operating under unsteady state conditions. The composting process was described, the input generated and lost energy terms as well as the relative importance of each term were quantitatively evaluated, and the composting phases were clearly identified. Results showed that the compost temperature peaked at 72 h of operation reaching 66.7 °C with a heat generation rate of 9.3 W·kg-1 of organic matter. During the composting process, the accumulated heat generation was 1.9 MJ·kg-1 of organic matter; only 4% of this heat was gained by the composting material, and 96% was lost outside the bioreactor. Contributions of thermal radiation, aeration, cylindrical, and side-walls surfaces of the reactor on the total heat loss were 1%, 2%, 69%, and 28%, respectively. The information obtained is applicable in the design, management, and control of composting operations and in improvement of bioreactor effectiveness and productivity. [ABSTRACT FROM AUTHOR]

Moisture sorption isotherms ( MSI) are required to optimize handling, drying, processing and storage of food products. MSI are obtained by solving nonlinear equations iteratively, which is normally a difficult process. A generic approach was successfully used for collective prediction of MSI for 12 cereals and five legumes simultaneously, by taking advantage of the superior computational capabilities of artificial neural networks ( ANNs). A total of 779 observations were collected from literature and used in training and validation of ANNs. The ANNs model used product type (grains or legumes), sorption state (adsorption or desorption), temperature and equilibrium moisture content as inputs to predict equilibrium relative humidity. A one- and two-hidden-layer ANNs were implemented. The overall prediction results obtained from ANNs were found to compare well with those reported for conventional analytical MSI models. The average prediction results obtained from the two-hidden-layer ANN for mean square error, deviation modulus and R2 were 0.009, 4.47% and 0.984, respectively. The results for each product compared well with those obtained from analytical MSI models. Four important issues that are commonly raised when implementing ANNs in prediction of MSIs were explained. These included preventing network over-fitting, minimizing the time and effort needed for ANN architecture optimization, validating reproducibility of the results and validating the network capability to predict new observations. Unlike conventional MSI models, ANNs used the same network to predict MSIs for several products simultaneously. The principle can be easily expanded to predict MSI for other larger sets of various products, which can save time and effort. Practical Applications Determination of moisture sorption isotherms ( MSI) is required for optimization of grain drying, processing, handling and storage operations. They can be also used to evaluate theoretical drying energy requirements and optimum storage conditions for a specific food product. In addition, they are used in food engineering calculations related to equipment design, shelf life evaluation and stability during storage operations. Determination of MSI for food products involves the use of conventional nonlinear MSI models, which requires an iterative solution methodology. The results are also specific to the food product investigated. Artificial neural networks were therefore proposed in this study as an alternative method for the collective prediction of MSI for some cereal grains and legumes. The method proposed in the study was accurate and reliable. In addition, it can be extended to larger varieties of food materials. [ABSTRACT FROM AUTHOR]

Huge quantities of palm tree residues are available annually in Saudi Arabia; they are often disposed of by burning, leading to large environmental pollution and health problems. Enclosed composting may be a successful method for utilizing these residues. Effective composting in a rotary bioreactor depends on the composting materials and the frequencies of the rotation–aeration process. Here, we attempted to determine the optimal method for composting these residues in a bioreactor. Four identical pilot-scale bioreactors (D1–D4) were used. The respective aeration–rotation frequencies were continuous (D1), and 20 min per 1 h (D2), 2 h (D3), and 3 h (D4); the rotation speed of the bioreactors was 3 rpm. Three periods were analyzed; their names and their respective lengths for D1, D2, D3, and D4 were as follows: the lag period was 10 h for each, the mesophilic periods were 13, 14, 89, and 231 h, and the thermophilic periods were 0, 55, 71, and 17 h. The peak compost temperatures (Tc, max) for D1, D2, and D3 were 65.2, 57.2, and 46.9 °C, and were achieved at 36, 71, and 108 h of operation, respectively. In D1, Tc quickly declined after reaching Tc, max due to limited microbial activity at Tc > 60 °C. In D2, a Tc of 50–57.2 °C was maintained for 61 h, and the highest organic matter degradation (OMD) of 0.30 was achieved. During the composting period, the carbon to nitrogen (C/N) ratio and moisture contents (MC) remained in the optimal ranges for microorganisms and did not affect the composting process. The results indicated that combined aeration–rotation for 20 min every hour (D2) gave the best results for composting palm tree residues, it ensured the hygiene safety of the end product, and it also consumed less power for aeration and rotation than D1. [ABSTRACT FROM AUTHOR]

Rotary drum composters are used to produce high-quality, pathogen-free compost without weed seeds. Insulation is usually applied to small-scale composters to warm up the composted materials and enhance metabolic reactions to produce stable and mature compost within a short time. However, the relationship between the composter size and the heat loss rate is still unclear. In this study, the relationship between the composter size (designated as the ratio of surface area to volume, As/V) and heat loss was analyzed and identified. To show the effect of insulation on the composting performance, two identical rotary drum bioreactors (each of As/V = 9) were used to compost tomato plant residues, one insulated and the other kept without insulation. Results showed that insulation increased the overall resistance against heat loss from the bioreactor from 0.37 (m2 °C W−1) to 1.12 (m2 °C W−1), quickly increasing the compost temperature, and a temperature of 55–67 °C could be achieved and remained for three days. Therefore, mature, stable, well-aged, and high-quality compost was obtained. In the non-insulated bioreactor, the compost temperature did not exceed 37 °C; this caused a decline of microbial activity and the composting process temperature was only in the mesophilic range, leading to a high risk of the existence of weed seeds and pathogens in the final immature compost. Insulation is necessary for laboratory-scale and small pilot-scale bioreactors (As/V ≥ 6), because heat loss is high as As/V is high, whereas it is not necessary for commercial full-scale bioreactors (As/V ≤ 4), because heat loss is minor as As/V is low. For larger pilot-scale bioreactors (As/V: 4–6), insulation cost must be considered when comparing the impact of energy saving on the composting process. [ABSTRACT FROM AUTHOR]