Degradation tests are one of the oldest approaches to quantifying storage ability without spending some months for a storage period. Samaras (1978) refers to publications around 1940. The product is cut into portions (slices) or grated and incubated with replicates for 10-11 days at 20°C. The dry matter loss, carbon dioxide development or visual modifications (changed color, growth of microbes) during incubation are taken as characteristics of the sample. The method of Samaras (1978) has been used in other studies with minor modifications: incubation at 30°C (Abele, 1987), just two days at 28°C (Wistinghausen, 1979) or five days at 22°C (Wistinghausen, 1984). The authors mentioned so far used vegetables in the test; other studies also used cereals (Samaras, 1981; Spiess, 1978). This test sometimes is called self-degradation which is not really an appropriate term. Not only inherent enzymes of the product are involved in the samples' decomposition but also the epiphytic, non-specific microflora.
 
Darkening of extract. This test is carried out mainly with potatoes and in a method tracing back to Pettersson (1970). Grated crude tubers are squeezed out, the juice is diluted with water (1:10), filtered and stored in the dark at 6°C. The extinction of the extract is determined at 530 nm at the beginning and during the next three to four days. The results are corrected for a standardized dry matter content of the tubers. The E48 value (extinction after 48 hours) is determined by a regression calculation. Modifications are published by Abele (1987): centrifugation of the extract (20 min at 6000 rpm), then dilution 1:19, measuring at 400 nm.
 
Electrical conductivity of extract. Details of this test, also applied to potato extract, have been received from Pettersson (Nordisk Forskningsring Järna, Sweden) by personal communication many years ago. The extract is stored in the dark at 20°C for daily readings of electrical conductivity over a period of at least six days. The final result is CD / C0 * 100 where C0 is the conductivity at the beginning and CD is the difference between the highest reading and C0.
 
References:

 
Pettersson, B.D. 1970. Verkan av växtplats, gödsling och tillväxtreglerande substanser på matpotatisens kvalitetsegenskaper. Nordisk forskningsring Meddelande Nr. 23
 
Samaras, F. 1981. Die epiphytische Mikroflora in Beziehung zu einigen biochemischen Merkmalen und zu einigen Kriterien der Verderbnisanfälligkeit ausgewählter Nahrungspflanzen, insbesondere Getreide. PhD Thesis Univ. Giessen; Publikation "Lebendige Erde", Darmstadt, Deutschland.
 
Samaras, I. 1978. Nachernteverhalten unterschiedlich gedüngter Gemüsearten mit besonderer Berücksichtigung physiologischer und mikrobiologischer Parameter. PhD Thesis Univ. Giessen; Publikation "Lebendige Erde", Darmstadt, Deutschland.
 
Spiess, H. 1978. Konventionelle und biologisch-dynamische Verfahren zur Steigerung der Bodenfruchtbarkeit. PhD Thesis Univ. Giessen; Publikation "Lebendige Erde", Darmstadt, Deutschland.
 
Wistinghausen, E.v. 1979. Was ist Qualität? Wie entsteht sie und wie ist sie nachzuweisen? Verlag Lebendige Erde, Darmstadt, Deutschland.
 
Wistinghausen, E.v. 1984. Düngung und biologisch-dynamische Präparate. Verlag Lebendige Erde, Darmstadt, Deutschland.