Rodica Caprita


RESEARCH ON SOME CHEMICAL ANALYSIS METHODS FOR EVALUATING THE SOYBEAN MEAL QUALITY

Rodica Caprita, A. Caprita

Abstract
Heat treatment of soybeans can reduce the activity of trypsin inhibitors and thereby improve the digestibility of protein. Overheating, however, may destroy or reduce the availability of certain heat sensitive amino acids and reduce the nutritional value of soy protein. The objective of our study was to compare three different chemical analysis methods for evaluating the soybean meal quality, and to establish the most suitable for evaluating over processing. Commercial SBM and raw soybean (granulation 200μ) were heated in a forced air oven at 120 ŗC for varying periods: 5, 10, 15, 20, 25, and 30 minutes. The urease index (UI), the KOH protein solubility and the Protein Dispersibility Index (PDI) were determined. Protein was determined by the burette method. We observed that the UI is useful to determine if the soybean meal has been heated enough to reduce the antinutritional factors, but it is not very useful for determining if soybean meal has been over-processed. A UI value of zero does not necessarily indicate over processing of SMB. KOH protein solubility is not a sensitive index for monitoring under processing of soybean meal. The KOH protein solubility changed very little up to first 10 minutes of heating and then decreased to a solubility of 65.20%. The PDI is the best method of evaluating these soybean ingredients for both under heating and over heating. PDI decreased incrementally from 78% to 20% for the heating times from 0 to 30 minutes. PDI is also the simplest measurement procedure of those that were evaluated.

Key words: urease index, protein solubility, soybean meal, protein digestibility

CERCETARI ASUPRA UNOR METODE DE ANALIZE CHIMICE PENTRU EVALUAREA CALITATII FAINII DE SOIA

Rodica Caprita, A. Caprita

Rezumat
Tratamentul termic al boabelor de soia reduce activitatea inhibitorilor tripsinei si astfel īmbunatateste digestibilitatea proteinei. Īncalzirea excesiva poate sa distruga sau sa reduca biodisponibilitatea unor aminoacizi termolabili si astfel sa reduca valoarea nutritiva a proteinei din soia. Cercetarile s-au efectuat pe soia toastata si soia netratata termic (granulatie 200 μ), care au fost īncalzite īntr-o etuva cu circulatie fortata a aerului, la temperatura de 120ŗC, perioade diferite de timp: 5, 10, 15, 20, 25 si 30 minute. S-au determinat indicele de ureaza (UI), solubilitatea proteinei īn KOH si indicele de dispersabilitate a proteinei (PDI). Proteina s-a determinat prin metoda biuret. Cercetarile au evidentiat ca indicele de ureaza este util pentru a determina daca faina de soia a fost tratata termic suficient pentru a reduce factorii antinutritionali, dar nu este util pentru determinarea supraprocesarii. Acest test nu este relevant pentru evidentierea īncalzirii excesive, deoarece indicele de ureaza zero nu indica neaparat supraprocesarea fainii de soia. Solubilitatea proteinei īn KOH nu reprezinta un indice precis pentru monitorizarea subprocesarii fainii de soia. Solubilitatea proteinei īn KOH s-a modificat foarte putin īn decursul primelor 10 minute de tratament termic iar apoi a scazut la solubilitatea de 65,20%. PDI este metoda cea mai buna de evaluare a fainii de soia atāt pentru subprocesare cāt si pentru supraprocesare. PDI a scazut progresiv de la 78% la 20% īn perioada de īncalzire de la 0 la 30 minute. PDI este de asemenea si cel mai simplu procedeu de determinare dintre cele studiate.

Cuvinte cheie: indice ureazic, solubilitatea proteinei, faina de soia, digestibilitatea proteinei