Weight loss of frozen bread dough under isothermal and ﬂuctuating temperature storage conditions Yuthana Phimolsiripol a,⇑ , Ubonrat Siripatrawan b , Donald J. Cleland c a Division of Product Development Technology, Faculty of Agro-Industry, Chiang Mai University, Chiang Mai 50100, Thailand b Department of Food Technology, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand c School of Engineering and Advanced Technology, Massey University, Private Bag 11-222, Palmerston North, New Zealand article info Article history: Received 30 January 2011 Received in revised form 12 April 2011 Accepted 18 April 2011 Available online 24 April 2011 Keywords: Frozen dough Weight loss Isothermal condition Fluctuating condition Artiﬁcial neural network Physical and kinetic models abstract Evaporative weight loss from food leads to both loss of saleable weight and quality deterioration so it need to be minimized. The effect of isothermal and ﬂuctuating conditions on frozen dough weight loss was measured and compared with kinetic, physical and artiﬁcial neural network (ANN) models. Frozen dough samples were regularly weighed during storage for up to 112 days in loose-ﬁtting plastic bags. The storage temperatures were in the range of 8 to 25 °C with ﬂuctuations of ±0.1 °C (isothermal), ±1, ±3 or ±5 °C about the mean. For each combination of temperature and ﬂuctuation amplitude, the rate of dough weight loss was constant. The rate of weight loss at constant temperature was nearly propor- tional to water vapour pressure consistent with standard theories for evaporative weight loss from pack- aged foods but was also accurately ﬁtted by Arrhenius kinetics. Weight loss increased with amplitude of temperature ﬂuctuations. The increase could not be fully explained by either the physic model based on water vapour pressure differences or the kinetic model alone. An ANN model with six neurons in the input layer, six neurons in hidden layers and one neuron in the output layer, achieved a good ﬁt between experimental and predicted data for all trials. However, the ANN model may not be accurate for product, packaging and storage systems different to that studied. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Use of frozen bread dough has grown rapidly. Frozen dough saves time, increases space availability and reduces equipment costs for the small retail or in-store baker who freshly bakes a wide variety of bread on the premises. Weight loss during frozen storage can be important in terms of reduction in quality and saleable weight. Frozen dough is generally stored at between 15 and 20 °C. Quality of frozen dough can be improved by controlling the freezing process and storage condi- tions (Yi and Kerr, 2009; Le Bail et al., 2010). Air blast freezing is the most commonly used, practical and reliable freezing process for frozen dough. No signiﬁcant dough differences were observed between freezing methods during the ﬁrst 11 weeks of frozen stor- age by Rosell and Gomez (2007). Slow freezing is usually recom- mended for frozen dough because faster freezing rates resulted in lowered bread quality in term of yeast damage and small loaf speciﬁc volume (Havet et al., 2000; Le Bail et al., 2010). The effect of freezing method on weight loss is likely to be very slight. Poten- tially the only mechanism would be via a difference in ice crystal size. Signiﬁcant changes in ice crystal size require large changes in freezing rate and crystal size changes tend to disappear during frozen storage. Shelf life of frozen dough should be 16 weeks if the dough has not been temperature abused during transportation and storage (Berglund et al., 1991). Surveys in the retail and the consumer stor- age sector suggest that high storage temperatures are common for frozen foods. The distribution of temperature in domestic freezers were as follows: 7% from 30 to 26 °C, 12% from 26 to 22 °C, 32% from 22 to 18 °C, 25% from 18 to 14 °C, 14% from 14 to 10 °C, 8% from 10 to 6 °C and 2% from below 6 °C(Taoukis and Giannakourou, 2004). Temperature ﬂuctuations during storage and transportation of frozen foods lead to accelerated reduction in food quality and shorter shelf life of the foods (Martins et al., 2004; Phimolsiripol et al., 2008). Temperature ﬂuctuations result from imprecision in the refrigeration system temperature control and defrost cycles. While the amplitude of air temperature variation can be quite large, product temperature ﬂuctuations are smaller due to their greater thermal inertia. Reid and Perez Albela (2006) reported that moisture migration of frozen food increased as both the average temperature and the magnitude of temperature ﬂuctuations increased during tempera- ture cycling. Pham (1987) found that weight loss of frozen lamb 0260-8774/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.jfoodeng.2011.04.020 ⇑ Corresponding author. Tel.: +66 53948236; fax: +66 53948230. E-mail address: yphimols@chiangmai.ac.th (Y. Phimolsiripol). Journal of Food Engineering 106 (2011) 134–143 Contents lists available at ScienceDirect Journal of Food Engineering journal homepage: www.elsevier.com/locate/jfoodeng