Food Sci. Biotechnol. 20(1): 1-6 (2011) DOI 10.1007/s10068-011-0001-1 Quality of Chilled Ready-to-Bake Pizza Stored in Air and under Modified Atmospheres: Microbiological and Sensory Attributes Preeti Singh, Ali Abas Wani, and G. K. Goyal Received: 10 February 2010 / Revised: 23 July 2010 / Accepted: 19 August 2010 / Published Online: 28 February 2011 © KoSFoST and Springer 2011 Abstract Modified atmosphere packaging (MAP) studies on microbiological and sensory analysis were conducted to extend the shelf life of ready-to-bake pizza stored at 7±1ºC. The gas combinations used were: atm1: air (control), atm2: CO 2 (100%), atm3: N 2 (100%), atm4: 50% CO 2 /50% N 2 . Total plate count (TPC), yeasts/molds (Y/M), coliforms, lactic acid bacteria (LAB), psychrotrophs, and anaerobic spore formers were estimated at time intervals of 0, 5, 10, 15, and 20 days. TPC and LAB of pizza samples (atm1) reached 7.10 and 8.14 log CFU/g after 10 days of storage, respectively. Coliforms, psychrotrophs, and Y/M were significantly higher (p<0.05) for pizza samples stored in atm1 than other storage conditions of MAP. Finally, counts of anaerobic spore formers were low (<3 log CFU/g) irrespective of the packaging conditions throughout the entire storage period. It was concluded that among the 4 atmospheres examined, atm2 (100% CO 2 ) was the best, followed by atm4>atm3>atm1 respectively, in descending order. MAP conditions under this study may extend shelf life of pizza to considerable amount of time. Keywords: modified atmosphere packaging, pizza, micro- biological quality, sensory evaluation, shelf life Introduction Changes in lifestyle, distribution patterns and the demand for increased food quality by the consumers have resulted in a desire to improve the shelf life of food products. Bakery products are widely consumed and therefore specifically defined requirements, for their quality characteristics, have been established. Their shelf life is mainly limited by microbial spoilage and staling (1). Recently, in order to achieve longer shelf life for bakery products, refrigerated conditions were employed to pre- baked or not baked dough, as well as new packaging technologies were developed and investigated (2). Modified atmosphere packaging (MAP) of food to extend its shelf life has been the subject of many investigations in recent years and studied exhaustively by various researchers. The technique involves packaging of the food product under the atmosphere of various combinations of gases such as carbon dioxide (CO 2 ), nitrogen (N 2 ), carbon monoxide (CO), sulphur dioxide (SO 2 ), etc; the most commonly used and perhaps the most effective being CO 2 with or without other gases (3). MAP technology has been particularly effective in chilled, short shelf life low-acid foods, especially minimally processed and highly perishable or semi-perishable foods (4). A high microbial load and storage temperatures higher than recommended for particular food can reduce the shelf life of a product by 50-70%. The elevated CO 2 levels can extends the lag phase of bacterial growth and slows the propagation of bacteria, while low O 2 favors mesophilic microbes such as Listeria and lactic acid bacteria (LAB) (5). It has been observed that 20-30% CO 2 or even 10% CO 2 level was effective to retard the bacterial growth (3) and higher levels of CO 2 were found to be more effective in inhibiting the growth of Staphylococcus aureus, Salmonella, Escherichia coli, and Yersinia enterocolitica. Preeti Singh ( ) Chair of Food Packaging, Technical University of Munich, 85354 Freising, Germany Tel: +49-8161-491212; Fax: +49-8161-491505 E-mail: preeti_ndri@rediffmail.com Ali Abas Wani Department of Food Technology, Islamic University of Science & Technology, 1-Avenue University, P.O. Box. 1418, GPO Srinagar, Awantipora, J&K, India G. K. Goyal Food Packaging Lab, Dairy Technology Division, National Dairy Research Institute, Karnal (Haryana), 132001, India RESEARCH ARTICLE