Nitrati v zelenjavi in spremembe v vsebnosti po skladiščenju in procesiranju

doktorska disertacija

Alenka Hmelak Gorenjak (Author), Janja Kristl (Mentor), Branko Kramberger (Thesis defence commission member), Martina Bavec (Thesis defence commission member), Tomaž Langerholc (Co-mentor)

Abstract

Namen disertacije je bil določitev realnih izhodišč za oceno vnosa nitratov s svežo, skladiščeno in procesirano zelenjavo in postavitev smernic za njegovo zmanjšanje. V ta namen smo validirali metodi za določanje nitratov s tekočinsko kromatografijo: EN 12014-4 in metodo po Chengu in Tsangu ter ju primerjali s standardno spektrofotometrično metodo EN 12014-7. Z validiranimi metodami smo določili vsebnost nitratov v vzorcih solate (Lactuca sativa L.), regrata (Taraxacum officinale agg. F.H. Wigg), špinače (Spinacia oleracea L.), belega zelja (Brassica oleracea var. capitata L. convar. capitata (L.) Alef. var. capitata L. fo. alba DC.), rdeče pese (Beta vulgaris L. subsp. vulgaris var. conditiva Alef., syn. B. vulgaris L. var. cruenta Wittm.) in krompirja (Solanum tuberosum L.). V raziskavo smo zajeli vzorce zelenjave različne pridelave, v različnih letnih časih, različnega izvora in sort. Vsebnost nitratov smo določili v v zorcih surove, skladiščene in procesirane zelenjave. Postopke obdelave zelenjave smo izvedli z 11 različnimi tehnikami v veliki kuhinji pod kontroliranimi pogoji in v velikih kisarnah zelja. Zaključke disertacije smo podali na osnovi analize 1043 podatkov o vsebnosti nitratov, nitritov (določeni po Griessu) in vitamina C (določen s tekočinsko kromatografijo s PDA detekcijo). Vsebnosti nitratov v vseh analiziranih vzorcih so znašale od 14 do 7513 mg/kg sveže snovi. Najvišje vsebnosti nitratov smo določili v rdeči pesi (2816 mg/kg), sledijo špinača (1682 mg/kg), solata (1529 mg/kg), belo zelje (374 mg/kg), regrat (195 mg/kg) in krompir z najnižjo določeno vsebnostjo nitratov (143 mg/kg). Shranjevanje ni imelo značilnega vpliva na vsebnost nitratov in nitritov v solati. Razmerje vsebnosti vitamin C/nitrat se je med skladiščenjem krompirja značilno znižalo za 48 %. Za oceno vnosa nitratov v človeški organizem je potrebno upoštevati vpliv tehnik obdelave na znižanje ali zvišanje vsebnosti nitratov glede na svežo zelenjavo. Po kuhanju upoštevamo 53 % znižanje vsebnosti nitratov za špinačo, 24 % znižanje za fermentirano zelje in 10 % za neolupljeno rdečo peso. Blanširanje špinače vpliva na 36 % znižanje vsebnosti nitratov, sotiranje na 25 % povišanje. Pripravljen pire iz kuhane špinače vsebuje 60 % manj nitratov kot sveža špinača, pire iz dušene špinače 30 % manj. Med fermentacijo zelja se vsebnost nitratov ni značilno spremenila. Na vnos nitratov v človeški organizem imata glavni vpliv vrsta zaužite zelenjave in način priprave.

Keywords

nitrati;solata;Lactuca sativa;špinača;Spinacia oleracea;belo zelje;Brassica oleracea var. capitata fo. alba;rdeča pesa;Beta vulgaris subsp. vulgaris var. conditiva;krompir;Solanum tuberosum;skladiščenje;procesiranje;

Data

Language:	Slovenian
Year of publishing:	2015
Typology:	2.08 - Doctoral Dissertation
Organization:	UM FKBV - Faculty of Agriculture
Publisher:	[A. Hmelak Gorenjak]
UDC:	635:546.173:641.51:612.3(043.3)
COBISS:	3860524
Views:	2956
Downloads:	426
Average score:	0 (0 votes)
Metadata:

Other data

Secondary language:	English
Secondary title:	Nitrates in vegetables and changes of their contents due to storage and processing
Secondary abstract:	The aim of the thesis was to set realistic guidelines for assessing the intake of nitrates in fresh, stored and processed vegetables, and to provide guidelines for its reduction. For this purpose, we validated two methods for determining nitrate content with liquid chromatography: EN 12014 -4 and the method by Cheng and Tsang, and compared them with a standard spectrophotometric method EN 12014-7. Using the validated methods we determined nitrate levels in samples of lettuce (Lactuca sativa L.), dandelion (Taraxacum officinale agg. F.H. Wigg), spinach (Spinacia oleracea L.), white cabbage (Brassica oleracea var. capitata L. convar. capitata (L.) Alef. var. capitata L. fo. alba DC.), beetroot (Beta vulgaris L. subsp. vulgaris var. conditiva Alef., syn. B. vulgaris L. var. cruenta Wittm.) and potato (Solanum tuberosum L.). The research included samples of vegetables grown in different seasons, by different means of production, and of various origins and varieties. The vegetables were processed using 11 different techniques in a large kitchen under controlled conditions and in large cabbage factories. The conclusion of the thesis is based on the analysis of 1043 estimates of nitrate, nitrite (determined by Griess) and vitamin C (determined by liquid chromatography with PDA detection) levels. In the whole sample, nitrate levels ranged from 14 to 7513 mg/kg fresh weight. The highest nitrate levels were determined in beetroot (2816 mg/kg), spinach (1682 mg/kg), lettuce (1529 mg/kg), white cabbage (374 mg/kg), dandelion (195 mg/kg), and potato (143 mg/kg). Storage did not have a significant effect on nitrate and nitrite levels in lettuce. In samples of potato, nitrate levels did not significantly change during storage, however, the ratio vitamin C/nitrate decreased by 48 %. Cooking is the most effective method for reducing nitrate levels in spinach (by 53 %), in fermented white cabbage (by 22 %), and in roots of beetroot (by 10 %). In samples of spinach, cooking and blanching significantly decreased nitrate content (by 36 %), whereas sautéing significantly increased it (by 25 %). Pureed cooked spinach had significantly lower nitrate levels than pureed sautéed spinach. Fermenting cabbage did not significantly affect nitrate content. Varieties of ingested vegetables and type of preparation both have a major impact on the intake of nitrates.
Secondary keywords:	nitrates;lettuce;spinach;white cabbage;potato;beetroot;storage;processing;
URN:	URN:SI:UM:
Type (COBISS):	Doctoral dissertation
Thesis comment:	Univ. v Mariboru, Fak. za kmetijstvo in biosistemske vede
Pages:	XVII, 162, [16] f.
ID:	8731112