205 Transactions of the Japan Society of Refrigerating and Air Conditioning Engineers, OriginalOriginal paperPaper Vol.35,No.3(2018),pp.205-210,Transactions of doi:the Japan10.11322/tjsrae.18-15FB_OA Society of Refrigerating and Air Conditioning Engineers, Received date: May 30, 2018; J-STAGE Advance published date: July 15, 2018 Received date: May 30, 2018; J-STAGE Advance publishied date: July 15, 2018 doi: 10.11322/tjsrae.18-15FB_OA Quality Changes of Commercial Surimi-based Products after Frozen Storage Ru JIA, Mami EGUCHI, Wei DING, Naho NAKAZAWA, Kazufumi OSAKO, Emiko OKAZAKI * Department of Food Science and Technology, Tokyo University of Marine Science and Technology (4-5-7 Konan, Minato-ku, Tokyo 108-8477) Summary In a preliminary study to clarify the factors affecting the quality deterioration of surimi-based products, the physical properties and drip loss of five different types of commercial surimi-based products (Itatsuki-kamaboko, Chikuwa, Satsuma-age, Datemaki, and Hanpen) at different freezing conditions were evaluated. After frozen storage, the breaking strength and breaking strain of Itatsuki-kamaboko, which is a two-stepÐheated surimi gel without starch, decreased with frozen storage, while for the other products, which are direct-heated gels containing starch, the breaking strength and breaking strain increased. Drip loss increased after frozen storage, and the thawing drip was higher with Itatsuki-kamaboko than with other products. These changes were notable in samples subjected to slow freezing than subjected to quick freezing. Moreover, the results of physical properties and drip loss corresponded to the change in sensory characteristics. Thus, the quality change in frozen surimi-based products might be correlated to not only the freezing conditions but also the heating methods and ingredients used. Keywords: Surimi-based product, Frozen storage, Freezing speed, Heating method, Physical property, Drip loss, Sensory evaluation 1. Introduction 2. Materials and Methods Low-temperature preservation (freezing in 2.1 Materials particular) is a common method used for many kinds Five types of typical commercial surimi-based of food, such as meat, fish, and seafood, to prevent products, Itatsuki-kamaboko (steamed kamaboko), physiological and chemical changes. Freezing is also Chikuwa (grilled kamaboko), Satsuma-age (fried important for commercial surimi-based products, kamaboko), Datemaki (grilled kamaboko with egg especially during periods of high demand, such as at yolk), and Hanpen (boiled kamaboko) were obtained the start of the new year in Japan, despite the belief from a supermarket (Tokyo, Japan). Samples and that gelled food like surimi-based products is their ingredients are listed in Table 1. Among them, susceptible to damage by freezing. Although reports Itatsuki-kamaboko is processed by two-step heating, have shown that protein denaturation, ice crystal and others are processed by direct heating. formation, etc., during freezing and frozen storage affect the quality of frozen meat or fish1-4), limited 2.2 Freezing and thawing information on the freezing of gelled products such Samples were cut into 25 mm cubes, vacuum- as surimi-based products is available, and the packed in plastic bags, and frozen either (A) quickly, relationship between freezing conditions and quality by immersion in −40¡C ethanol or (B) slowly, by changes in surimi-based products has not been freezing in a −20¡C freezer. The frozen samples clarified. were stored at −20¡C for 2 and 21 days and thawed Currently, surimi-based product manufacturers at 4¡C overnight before use. establish freezing conditions based not on scientific evidence but on experience. Thus, there is a need to 2.3 Determination of physical properties clarify the quality changes in surimi-based products The physical properties of samples were evaluated during freezing and frozen storage and provide by the puncture test using a rheometer (RE2-3305B; manufacturers with a scientific basis for optimal Yamaden Co., Tokyo, Japan). The plunger was processing conditions. In this study, as the first step spherical, with a diameter of 5 mm and a depression of the investigation to clarify the factors affecting speed of 1 mm/s. Samples were kept at 0¡C and the quality deterioration of frozen surimi-based measured for breaking strength (g) and breaking products, we investigated the quality changes in five deformation (mm). Each measurement was repeated different types of commercial surimi-based products four times. during frozen storage, comparing the changes in physical properties, drip loss, and sensory characteristics. Fax:+81 3-5463-0618 E-mail: eokazaki＠kaiyodai.ac.jp －65－ 206 Table 1. Kinds of kamaboko Sample Product name Ingredient Heating method A Itatsuki-kamaboko Surimi (Croaker), Sugar, Mirin, Egg white, Salt, Steamed (Two-step Seasoning; heating) B Chikuwa Surimi, Potato starch, Sugar, Egg white, Glucose, Salt, Grilled (Direct heating) Vegetable oil, Lard, Seasoning; C Satsuma-age Surimi (Herring, Cod, Horse mackerel, Croaker, others), Fried (Direct heating) Soybean protein, Potato starch, Glucose, Seafood extract, Salt, Seasoning, Sugar, Vegetable oil; D Datemaki Egg, Surimi, Sugar, Egg white, Seasoning, Starch, Grilled (Direct heating) Seafood extract, Salt, Modified starch, Emulsifier; E Hanpen Surimi, Egg white, Starch, Sugar, Yam, Mirin, Boiled (Direct heating) Vegetable oil, Salt, Seafood extract, Thickening polysaccharides, Spice, pH regulator 2.4 Determination of drip loss Traditionally, physical properties, including Drip loss included thawing drip (TD) and breaking strength and breaking deformation, are the expressible drip (ED). The TD was determined by main functional properties of surimi-based products. measuring the sample weight (W1) and drip weight These properties are also primary indicators of the (W2) of samples using No. 5 filter paper and was quality of surimi-based products6-9). calculated using equation (1). The breaking strength and breaking deformation TD (%) = W2/W1 × 100 (1) results for five commercial surimi-based products The ED was measured based on the method of before freezing are shown in Fig. 1. It was suspected Shimizu5) with slight modifications. A slice of that the change after 2 days would reflect the effect sample (2 mm thick and approximately 1.0 g in of freezing itself, and the change after 21 days weight) was placed between two filter papers for a would reflect the effect of frozen storage at −20¡C. compression test on a RE-3305B rheometer under 10 The breaking strengths for Itatsuki-kamaboko, kg/cm2 pressure for 20 s. Samples were weighed Chikuwa, Satsuma-age, Datemaki, and Hanpen were before (W1) and after compression (W2), and the 790, 293, 196, 84, and 80 g, respectively. In the ED was calculated using equation (2). processing of surimi-based products, grinding with ED (%) = ((W1 − W2)/W1) × 100 (2) salt and heating are the most important steps10). Grinding with salt can increase the ionic strength of 2.5 Sensory evaluation fish meat, thus increasing actomyosin solubility and Commercial products (Itatsuki-kamaboko and generating a sol form. Heating below 40¡C, called Chikuwa) were obtained from a supermarket, Òsuwari,Ó can change its rheological properties from subjected to slow freezing and stored at −20¡C. the sol form to gel11). Due to the formation of a Frozen samples were then thawed at 4¡C overnight protein network structure, heating at high after 2-week frozen storage. Sensory evaluation of temperatures after suwari heating (two-step heating) samples before and after frozen storage was produces increased gel strength12). Therefore, due to performed by nine panelists from the Food the two-step heating processing method of Itatsuki- Processing Laboratory of Tokyo University of kamaboko13), it had the highest breaking strength Marine Science and Technology. The panelists before freezing. Chikuwa is typically heated at 130Ð included four males and five females aged 20 to 40. 180¡C until the center temperature reaches 75¡C; The appearance, elasticity, smoothness, and moisture Satsuma-age is heated to 160Ð200¡C in oil; Hanpen levels were evaluated, comparing thawed samples to is boiled at 85Ð90¡C; and Datemaki is grilled. unfrozen samples. A seven-point scale was used: 3, Therefore, these four surimi-based products heated much stronger; 2, somewhat stronger; 1, slightly by direct heating had low breaking strength. These stronger; 0, unchanged; −1, slightly weaker; −2, results are consistent with previous studies9, 14, 15). somewhat weaker; and −3, much weaker) to Furthermore, Fig. 1 shows a high correlation evaluate each item. coefficient (R = 0.9784) between breaking deformation and breaking strength. These results 3. Results and Discussion indicate that surimi-based products with higher breaking strength had larger deformation values. 3.1 Physical properties Similar results were observed by Qian16). －66－ 207 The breaking strength results of five surimi-based 1000 products, frozen quickly and slowly and stored for 2 and 21 days, are shown in Fig. 2. The breaking 800 A strength of Hanpen did not significantly change during frozen storage; however, for Datemaki, 600 Chikuwa, and Satsuma-age, which were processed with direct heating, the breaking strength increased 400 during frozen storage, by 67.9%, 43.7%, and 23.6%, B respectively, compared to that before freezing. Breaking strength (g) strength Breaking 200 C Conversely, for Itatsuki-kamaboko, which was E D processed with two-step heating, the breaking 0 strength