POST-HARVEST TECHNOLOGY Mechanical Properties of Potatoes from Organic Farming

Marianna Németh, Karl-Hans Kromer, Bonn
A fter rice, wheat, and maize, the potato is the most important kind of basic food worldwide and the most significant starchcontaining tuber crop [1]. From the viewpoint of nutritional physiology, it belongs to the ideal kinds of basic food which are part of a nutritious diet [2]. Worldwide, potatoes are grown on a cultivated area of approximately 18.8 million ha in 150 out of 200 countries. In the past years, production has remained stable [3]. An increasing degree of mechanization leads to
more » ... ization leads to growing mechanical load on the potato tubers, which results in an increasing danger of damage to the tubers, the consequences of which are secondary infection as well as mass-and quality losses [4]. For this reason, potato varieties of high firmness are also being sought in organic farming. In all areas of potato production and -processing, high product quality is required. In order to supply the consumer with high-quality food potatoes, it is necessary to maintain freshness and quality for a long time after the harvest. Hence, storage technology is one of the most important branches of both agriculture and the food industry. Efficient quality management needs suitable quality parameters for both fresh and stored potatoes. The environmental performance of the cultivation technique is a suitable quality criterion. As compared with conventional products, organic farming products are often considered to be of higher quality, and their cultivation is promoted by agricultural policy. For this reason, a group of DFG researchers was intended to develop optimization strategies in organic farming. The following report contains selected results of the determination of mechanical potato properties. For various purposes, the mechanical properties of agricultural products are measured using standardized methods [5, 6, 7]. The variety of different methods and techniques, such as pressure-, compression-, penetrometer-, shear-, and stress tests, are suitable for the description, characterization, and determination of texture, firmness, crispness and, hence, quality. The collective term of mechanical properties comprises all those properties which are connected with behaviour under the effect of forces. Like all agricultural materials, the potato tuber from organic farming is a complex biological system with great variability. The composition, the dry matter content, and the tissue structure of these materials vary during growth, maturation, and storage. These influencing factors were given for the agricultural engineering trials and kept constant to the largest possible extent by the group of agronomical researchers [8]. Significant cultivation factors for high yields and high potato quality are the choice of varieties and organic fertilizing (Norg). Since primarily the effect of mineral fertilizers on potato firmness and, hence, -quality has been examined in the past decades, recent studies on the explicit effect of organic fertilizing are virtually not available [9, 10]. Working Hypotheses The planning of the experiments was based on working hypotheses of the group of researchers. The demands of the consumers with regard to food quality are growing. The environmental compatibility of a cultivation technique is considered an additional quality criterion. Firmness and texture of agricultural products are suitable criteria for the evaluation of their quality. Pendulum-, penetrometer-, and plate tests are used to assess potato tubers on the basis of their mechanical properties. This study was intended to clarify to what extent these techniques of firmness measurement are also suitable for potatoes from organic farming. Trials were carried out over three years to prove the influence of the variety, organic fertilizer application, and storage duration on the firmness properties of the potato tuber. Summarized contribution to LANDTECHNIK. You will find the long version under Keywords Mechanical properties; penetrometer-, pendulum-, plate test; quality of potatoes; organic farming Literature Literature references can be called up under LT 04209 on the internet Fig. 1: Energy uptake of pendulum versus variety and fertilising levelstorage time 120 days (pendulum test 1998)