The base colour of fruit as an indicator of optimum harvest date for two apple cultivars (Malus domestica Borkh.)
The CIE L* a* b* colour system is used to evaluate food colours. Its advantage is that the base skin colour in apples can be measured on the same fruit before and on the optimum harvest date. The aim of the research conducted between 2002 and 2006 was to evaluate a quick and non-destructive method of determining the optimum harvest date of apples intended for long storage based on the changes observed in the base skin colour. Another important research aspect was to compare this method with other methods or indicators used to determine the harvest date. The colour measurement was conducted on two apple cultivars, Šampion and Royal Gala, with the aim of, amongst other factors, establishing a standard for each that could be used in practice in fruit production. From amongst the evaluated colour indicators L*, a*, b*, Hueab angle and chroma, changes in the base colour were best illustrated by the a* coordinate value and Hueab angle value. Based on the evaluation of the quality of fruits after storage, it can be stated that the fruits had the best quality when the a* coordinate during harvest ranged between -7 and -8 for ‘Šampion' and between -3 and -5 for ‘Royal Gala’. The Hueab angle assumed a value between 100 and 101 for ‘Šampion' and between 96 and 99 for ‘Royal Gala’ during the optimum harvest date. Therefore, the a* coordinate and the Hueab angle can be used to indicate harvest maturity.
The measurement of ethylene concentration in the apple core is considered a good method of determining OHD, but requires high accuracy and expensive equipment. The measurement of ethylene production seems to be a technologically easier method. During research conducted in the years 2003-2008, measurements of ethylene production were evaluated as a method for determining the harvest maturity of ‘Jonagored’ apples intended for storage. Measurements were carried out every 4-5 days starting a few weeks before the estimated harvest date. Apples were picked on four dates and after five months the loss of mass, firmness, TSS and TA was measured, the incidence of physiological disorders and fungal diseases was assessed and sensory tests were conducted to evaluate storability. Based on this evaluation it was determined which of those dates was OHD. After a period of low ethylene production, the production accelerated rapidly to reach an average level between 10.0 and 12.5 ppm kg-1 hr-1 on the OHD. Later, ethylene production rose still more sharply and quickly reached several dozens of ppm kg-1 hr-1. The accuracy of the new method was compared with other methods used to determine the maturity stage. The results obtained through the measurement of ethylene production showed the least deviation from the six-year average and only the results obtained using the Streif index method, which may be unreliable for some cultivars according to the literature, had a comparable margin of error.
Research was carried out during the 1999-2007 growing and storage season using ‘Ligol’ apples from trees grafted on M.26, and fertilised in accordance with recommendations for commercial orchards. The approximate optimum harvest date was determined mainly on the basis of starch index measurements and Streif index calculations, evaluated 7-8 times every 4-5 days each year. In addition to samples collected to determine OHD each year, there were four harvests of fruit intended for storage. The apples were stored in a cold storage room at 1-2°C and RH of around 90% for about five months. Following a storage period lasting the same number of days for each harvest, the quality of fruits was examined and the correlation between the concentration of minerals in apples and all fungal diseases and physiological disorders was calculated. In years with high precipitation in the period preceding the harvest, the share of fruits affected by fungal diseases and physiological disorders after storage depended more on weather conditions prevailing in the growing season than on the harvest date. The incidence of bitter pit increased with the number of days preceding OHD. Other recorded losses were caused by internal breakdown and superficial scald, but they were small and did not seem significant for ‘Ligol’ apples. Each characteristic mineral concentration in the fruit at harvest (N, P, K, Ca and Mg) was correlated with the incidence of physiological disorders and/or fungal diseases. The incidence of bitter pit and lenticel blotch pit and the sum of physiological disorders increased along with the increase in nitrogen concentration. The feature that best predicted the storability of ‘Ligol’ was the K/Ca ratio.
Wheat kernel is made up of structures of different apparent viscosities with varied ability to withstand stress and dissipate strain energy. Its complex mechanical behaviour determines technological susceptibility and is important for wheat quality assessment. The aim of the study was the examination of the Peleg and Normand model to characterize the overall stress relaxation behaviour of wheat kernel at varying loading conditions. The relaxation experiments were made with a help of a universal machine Zwick Z020 in compression at four distinct initial load levels, i.e., 20, 30, 40, and 50 N. The measurements were made for intact wheat kernels at seven levels of moisture content. Relaxation characteristics were approximated with the help of Peleg and Normand formula. An interactive influence of the load level and moisture on Peleg and Normand constants have been confirmed. The initial loading level had none or only slight effect on the model coefficients (Y(t), k1 and k2). The parameters of the Peleg and Normand model decreased with the increase of water content in kernels. For moist kernels, a higher amount of absorbed compression energy was relaxed, since less energy was necessary to keep the deformation at a constant level.
Ryszard Kulig, Grzegorz Łysiak, Zbigniew Krzysiak, Monika Wójcik and Renata Różyło
This paper presents the results of pea straw compaction efficiency tests. The compliance of the tested material to pressure agglomeration was assessed depending on the compaction pressure used (45-113 MPa). The compaction was carried out using a Zwick testing machine, type Z020/TN2S, and a closed die pressing unit. It was found that, along with the pressure increase, the material density in the chamber increased (from 1.255 to 1.76 g∙cm−3), as well as the agglomerate's density (from 0.739 to 1.05 g∙cm−3) and the product's mechanical resistance (from 0.31 to 0.69 MPa). Increasing the compaction pressure in the analyzed range increased the unit value of compaction work, from 17.16 to 34.27 J·g−1.
Grzegorz P. Łysiak, Robert Kurlus and Anna Michalska
The aim of this research was the evaluation of whether the application of 5-ALA, which has potential as a plant growth stimulating agent with indirect anti-stress activity, can limit the damage caused by low temperatures in winter. The research was conducted on frost-sensitive apple cultivars for three years in an orchard and in a laboratory. During the vegetative seasons of each year, the trees of three apple cultivars (‘Golden Delicious’, ‘Gala’ and ‘Šampion’) were subject to 5-ALA foliar application. Three times during each winter following the field application, apple shoots were taken to the laboratory and frozen at −20°C, −25°C and −30°C. After incubation, the damage to the sensitive parts of the shoots was evaluated. The application had a positive effect on the frost resistance of all cultivars, most often at the end of dormancy, which is especially noteworthy because frost damage occurs most frequently during this period. Positive effects of the application were found in most of the experiment combinations of cultivar, year, freezing date and shoot part. Additionally, the positive influence of 5-ALA application on frost resistance was found to increase with each year of the research.