Eur Food Res Technol (2006) 223: 387–393 DOI 10.1007/s00217-005-0216-6 ORIGINAL PAPER Ays ¸eg¨ ul Kırca · Oktay Yemis ¸ · Mehmet ¨ Ozkan Chlorophyll and colour changes in grapevine leaves preserved by passive modification Received: 5 September 2005 / Revised: 22 November 2005 / Accepted: 1 December 2005 / Published online: 13 January 2006 C  Springer-Verlag 2005 Abstract Grapevine leaves are used to prepare the dish called as “dolma,” i.e., a Turkish term for stuffed veg- etable. Our study was undertaken to monitor the desir- able colour changes from bright-green to olive-yellow in grapevine leaves stored under modified atmosphere (pas- sive modification). We also determined whether micro- bial growth occurred after a prolonged storage (9 mo) at 20 ◦ C. For this purpose, grapevine leaves from two com- mon varieties grown in Turkey were placed in hermetically- sealed glass jars and stored at 20 ◦ C for 9 mo. Since the colour is the most important quality criteria for grapevine leaves, the changes in chlorophyll-a and chlorophyll- b, and colour variables were monitored during storage. Chlorophyll-a and -b were identified and quantified by HPLC. Chlorophyll-b was more stable than chlorophyll-a in both varieties studied. Compared to varieties, chloro- phylls in Narince variety were less stable than those in Sul- tani variety. Since consumers expect olive-yellow colour in grapevine leaves, Narince variety is more suitable for this technique. Excellent correlation was found between −a ∗ /b ∗ colour variable and chlorophyll-a concentration (r=0.9829–0.9832). Mesophilic bacteria were found to be low level (3.2×10 1 cfu/g), whereas yeast and molds, lactic acid bacteria and Enterobacteriaceae were below the low- est detection limit (<10 cfu/g) in the leaves stored at 20 ◦ C for 9 mo. The results suggest that passive modification is very effective to achieve the desirable colour transforma- A. Kırca Department of Food Engineering, Faculty of Engineering and Architecture, C ¸ anakkale Onsekiz Mart University, Terzio˘ glu Campus, 17020 C ¸ anakkale, Turkey O. Yemis ¸ · M. ¨ Ozkan () Department of Food Engineering, Faculty of Engineering, Ankara University, Diskapi Campus, Diskapi, 06110 Ankara, Turkey e-mail: ozkanm@eng.ankara.edu.tr Tel.: +(90)-312-596-1146 Fax: +(90)-312-317-8711 tion of grapevine leaves in a very short period of time (2–6 days) depending on the variety. Moreover, this simple tech- nique gives rise to a product with good microbial quality. Keywords Grapevine leaves . Chlorophyll-a . Chlorophyll-b . −a ∗ /b ∗ . Microbial quality Introduction Colour is a very important quality attribute of both raw and processed fruits and vegetables. During food process- ing, structural characteristics of natural pigments are often modified; as a result, the colour of the final product is altered [1]. Therefore, numerous studies have been conducted to show the degradation mechanisms of naturally occurring pigments in foods. Among the natural pigments, chloro- phylls are the most widely distributed pigment in nature. The major chlorophylls in foods are chlorophyll-a (chl-a) and chlorophyll-b (chl-b), and chl-a is usually present in foods at a concentration 2–3 times higher than chl-b. The chlorophyll molecule is sensitive to heat, oxygen, light and acid degradation due to its long chain of conju- gated carbon–carbon double bonds [2]. Although chloro- phylls can be modified in many ways, the most common modification during food processing occurs through pheo- phytinization, i.e., the replacement of the central magne- sium ion by two hydrogen ions and the consequent for- mation of the olive-brown coloured pheophytins [3]. This reaction is favoured by prolonged heat treatments, such as blanching and canning, as well as prolonged storage [4]. The second common pathway for chlorophyll conver- sion occurs through the removal of phytol from chlorophyll and pheophytins by the action of enzyme chlorophyllase, resulting in the less stable chlorophyllides and pheophor- bides, respectively [5]. Processing of most green vegetables is optimized to minimize chlorophyll degradation. How- ever, for some products, such as cucumber picklings, olives, okras, and grapevine leaves the conversion of chlorophylls to pheophytins and pheophorbides is highly desirable [6].