Yield and tuber quality performance of eight European potato (Solanum tuberosum) cultivars in a short-day temperate climate

The potato cultivar base is quite wide in South Africa as new genotypes often are adopted from European countries. However, the performance of many cultivars is not well-understood, and this is compounded by agro-climates and changes in the climate. The aim of this study was to evaluate the yield and potato quality performance of seven recently introduced European cultivars (Panamera, Electra, Savanna, Navigator, Melanto, Sifra and Innovator) against Mondial (a well-established cultivar in the country) to inform cultivar selection decisions in the potato industry. The experiment was conducted in Pietermaritzburg, under temperate agro-climatic conditions in a randomised complete block design. Results showed significant (P≤0.05) differences among cultivars, with Innovator having the highest dry matter content (20%) and specific gravity (1.063). Electra and Navigator had the highest and lowest yields (54 and 21 t/ha), respectively. All cultivars had a low occurrence of internal defects (≤ 10%) and produced high marketable yield (≥ 80%). These results suggest five out of the eight cultivars to be economical for production in the region. Only Navigator, Panamera and Savanna did not exceed the 35 t/ha yields currently achieved in the country

Electrical properties of maize kernels contaminated with aflatoxin

The purpose of this study was to investigate the effect of aflatoxin contamination on the dielectric constant of maize kernels. A factorial experiment comprising of three levels of moisture content (13.3, 15.3, and 16.4%), three frequencies (25, 50, and 100 kHz), and nine levels of aflatoxin contamination (0, 1.5, 2.6, 10, 50, 100, 150, 172, and 230 μg/kg) was used. The maize kernels were poured into a custom-built sample holder comprising a shielded parallel plate capacitor. An ISO-TECH LCR-821 meter was used to measure the capacitance, from which the dielectric constant was computed. The results indicated that moisture content and frequency significantly (p ≤ 0.05) affected the dielectric constant. The dielectric constant increased with increase in moisture content and decreased with increasing frequency. However, aflatoxin contamination level had no significant (p > 0.05) effect on the dielectric constant of maize kernels. The coefficient of determination (R2) of dielectric constant and aflatoxin contamination levels was low (R2 = 0.2687), indicating a poor correlation between the aflatoxin levels and the dielectric constant of maize kernels. Based on the findings, the dielectric constant is unsuitable for predicting the level of aflatoxin contamination in maize kernels within the 20 – 200 kHz frequency range

Evaluation of the Effects of Different Packaging Materials on the Quality Attributes of the Tomato Fruit

Post-harvest loss continues to be a significant problem in the food industry. Different packaging materials, designed to reduce fruit damage, are anticipated for various applications in the supply chain. Recently, stamped paper (SP) and expandable polystyrene (EPS) trays have been introduced as tomato retail packaging. Although the combination of paper trays and clear plastic are still not 100% biodegradable packaging, they are promising alternatives to the heavy utilisation of petrochemical-based polymers. This study investigated the effects of different packaging materials and storage conditions on the ‘Nema-Netta’ tomatoes’ quality attributes. The treatments consisted of a stamped paper (SP) + polyvinyl chloride (PVC), expandable polystyrene (EPS) + polyvinyl chloride (PVC), stamped paper (SP)+ flow wrap, expandable polystyrene (EPS) + flow wrap, polypropylene (PP), and unpackaged tomatoes stored at cold and ambient conditions. Firmness, physiological weight loss (PWL), pH value, titratable acidity (TA) and total sugars were evaluated at seven-day intervals, over 28 days. Temperature and relative humidity at cold storage ranged between 8–12 °C, 78–80% RH and 22–26 °C, 68–72% RH at ambient storage conditions. The packaging and storage conditions significantly affected the PWL, firmness, pH, TA and total sugars. Samples in the EPS Tray combined with the PVC wrap at cold storage maintained the quality of the tomatoes better than the other packaging. The combination of packaging and cold storage created an ideal environment for maintaining the quality of tomatoes. The relative differences between EPS Tray + PVC (non-biodegradable) and SP Tray + PVC (biodegradable) were less than 5% in multiple tests

Evaluation of the Effects of Different Packaging Materials on the Quality Attributes of the Tomato Fruit

Post-harvest loss continues to be a significant problem in the food industry. Different packaging materials, designed to reduce fruit damage, are anticipated for various applications in the supply chain. Recently, stamped paper (SP) and expandable polystyrene (EPS) trays have been introduced as tomato retail packaging. Although the combination of paper trays and clear plastic are still not 100% biodegradable packaging, they are promising alternatives to the heavy utilisation of petrochemical-based polymers. This study investigated the effects of different packaging materials and storage conditions on the ‘Nema-Netta’ tomatoes’ quality attributes. The treatments consisted of a stamped paper (SP) + polyvinyl chloride (PVC), expandable polystyrene (EPS) + polyvinyl chloride (PVC), stamped paper (SP)+ flow wrap, expandable polystyrene (EPS) + flow wrap, polypropylene (PP), and unpackaged tomatoes stored at cold and ambient conditions. Firmness, physiological weight loss (PWL), pH value, titratable acidity (TA) and total sugars were evaluated at seven-day intervals, over 28 days. Temperature and relative humidity at cold storage ranged between 8–12 °C, 78–80% RH and 22–26 °C, 68–72% RH at ambient storage conditions. The packaging and storage conditions significantly affected the PWL, firmness, pH, TA and total sugars. Samples in the EPS Tray combined with the PVC wrap at cold storage maintained the quality of the tomatoes better than the other packaging. The combination of packaging and cold storage created an ideal environment for maintaining the quality of tomatoes. The relative differences between EPS Tray + PVC (non-biodegradable) and SP Tray + PVC (biodegradable) were less than 5% in multiple tests

Effect of Modified Atmosphere Packaging on Microbiological, Physiological and Chemical Qualities of Stored Carrot.

Optimum packaging film for carrots should lead to low condensation, but preventing moisture loss, and maintain optimum gas composition during the storage period. In this study, carrots were packaged in polypropylene (PP) and low density polyethylene (LDPE) films and stored at 0¼C and ambient temperature (15-25¼C). After 7 days of 0¼C storage headspace O2, CO2 and N2 concentrations were 11.85%, 13.38%, and 6.69% for PP films and 3.39%, 3.24% and 4.77% for LDPE films. On the other hand, after 7 days of ambient temperature storage O2, CO2 and N2 concentrations were 6.78%, 28.31%, and 16.15% for PP films and 6.41%, 5.19% and 5.28% for LDPE films. The higher the CO2 content of the headspace the more the sucrose content decreased while the glucose and fructose content changed slower. A general decrease of the sugars (sucrose, glucose and fructose) was observed for all samples packaged in PP. The free sugars in carrots were observed to decrease at a slower rate for packaging in LDPE. Based on these results, it was concluded that LDPE film allowed lower respiration rates and is preferred to the PP material. The number of total aerobic microorganisms was higher in packages stored under ambient conditions than in those stored at 0ºC temperature. The lowest counts were observed in the least permeable packaging film (PP) up to day 14. The total number of populations of coliform was higher with PP and LDPE films stored under ambient conditions as compared to those stored at OºC. Packaging films with relatively higher permeability to O2 and CO2 are preferred for maintaining normal respiration of carrots without the occurrence of secondary decomposition during storage. Modified atmosphere packaging combined with low temperature storage of carrots (about 1¼C) reduces both biological and biochemical activities resulting in improved keeping quality. The Journal of Food Technology in Africa Volume 6 No.4, 2001, pp. 138-143 KEY WORDS: Modified atmosphere packaging, polypropylene, low density polyethylen

Modelling effects of pre-storage treatments, maturity stage, low-cost storage technology environment and storage period on the quality of tomato fruit

The aim of this study was to develop a model for prediction of the quality of tomato during storage. Two storage conditions (evaporatively cooled and ambient), four disinfection treatments (tap, anolyte, hot and chlorinated water) and three maturity stages (green, pink and red) were employed in this experiment. Using multivariate analysis, the principal components (PC) (PC1, PC2) were analysed. The PC1 and PC2 contributed 47.9% and 26.0% of total variation, respectively. Maturity stages and the disinfection treatments had significant (p < 0.05) influence on PC1 and PC2. Non-linear fractional and polynomial models were fitted to the experimental data to screen the best models. Hue angle, firmness, titratable acidity (TA) and total soluble solid:TA demonstrated non-linear relationship with days of storage. TA, hue angle and firmness of tomatoes fitted well to the models developed. The models are recommended for use by tomato farmers to predict changes in the quality parameters

An overview of biogas production : fundamentals, applications and future research

Due to the increase in population, both developed and developing countries are facing mainly issues surrounding the future energy security and a better use of natural resources. Such present and future energy problems can be solved by the use of renewable energy sources. Among several renewable energy sources is a sustainable means of anaerobic digestion for production of gases. In the past, anaerobic digestion as a source of biogas was used mainly for degradation of waste materials or toxic compounds. However, recently, there has been great interest in producing biogas from energy crops. This paper presents an overview of state-of-the-art and future viewpoints related to the anaerobic digestion process for biogas production

Effect of infield handling conditions and time to pre-cooling on the shelf-life and quality of tomatoes

<div><p>Abstract This study investigates the effects of post-harvest handling practices prior to storage on the quality of tomatoes in South African supply chains. Pink mature tomatoes were harvested in the morning and afternoon, transported from two farms located 40 km apart to two central pack houses located near each of the farms in Limpopo, South Africa. The samples were transported using bins (468 kg capacity) and lugs (20 kg capacity). After harvesting, the samples were either immediately transported to the pack house and precooled within two hours, or left in the field and transported to the pack house to be pre-cooled after six hours, to simulate delays during transportation. On arrival at the pack houses, the fruit was sampled from the bottom 0.15 m of each lug or bin, precooled using forced air and washed. After precooling, the samples were stored either under ambient conditions or refrigerated storage (15±2 °C). The tomato colour, firmness, weight loss, marketability and pH were monitored over a 24-day storage period. The rate of change of the fruit hue angle was significantly (p ≤ 0.05) higher for samples handled using bins as compared to those handled using lugs. Handling conditions had no significant (p > 0.05) effect on the rate of loss of fruit flesh firmness. The bottom layer of fruit stored in bins showed 30% mechanical damage as compared to 2% in lugs. Harvesting in the morning and pre-cooling within two hours improved fruit marketability and weight-loss by up to 200 kg/ton and 75 kg/ton, respectively, as compared to harvesting in the afternoon and pre-cooling after six hours. As the best practices for industry, the study recommends minimizing the time to pre-cooling, harvesting in the morning and using lugs to handle the fresh tomatoes.</p></div