The effects of industrial pre-frying and domestic cooking methods on the nutritional compositions and fatty acid profiles of two different frozen breaded foods

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Abstract

This study was carried out to determine the effects of manufacturer pre-frying in olive and sunflower oil, as well as domestic cooking methods (deep-frying in olive and sunflower oil and baking) on the proximate compositions and fatty acid profiles of tuna pasties and ham nuggets. The pre-frying processes reduced moisture and carbohydrates and increased ash, fat and protein content in both pre-fried products. During cooking, the frying processes caused a reduction in moisture content and an increase in fat content in relation to pre-fried samples, while baking did not modify the proximate composition. The fatty acid profiles of products during both the pre-frying and frying processes became similar to those of the culinary fat used. Thus, the frying processes reduced the proportion of saturated fatty acids (SFA) and increased the proportion of monounsaturated fatty acids (MUFA) in the foods when olive oil was used, whereas increased the proportion of polyunsaturated fatty acids (PUFA) in products fried in sunflower oil. The fatty acid profiles of fried samples tended to be more similar to the frying fat than to the pre-frying fat, whereas the fatty acid profiles identified during the pre-frying process for baked products were not significantly modified. Thus, samples pre-fried in olive oil and subsequently baked showed the best proportion of fat content and PUFA/SFA, MUFA + PUFA/SFA and n-6/n-3 ratios of the tested products.

Introduction

The growing tendency to spend less time on food preparation has led to a great demand for time-saving “ready-to-heat” frozen products. Thus, breaded foods are very popular today, and their consumption has increased in recent years both in high-convenience consumer societies and in developing countries (Varela, Salvador, & Fisman, 2008). When breaded foods are prepared, there are significant changes in their macronutrient compositions (Weber, Bochi, Ribeiro, Victório, & Emanuelli, 2008). At present, these products are often commercially pre-fried, as deep-fat frying is the most common way to prepare breaded frozen foods. During frying, the culinary fat or oil becomes an important ingredient of the fried food because water is lost and oil penetrates into the food (Ramírez and Cava, 2005, Varela and Ruiz-Rosso, 2000). Thus, the high amount of culinary fat absorbed during the frying process can, in some cases, 1/3 of the total weight of the final food product (Mellema, 2003), dramatically change the fatty acid profile of the food (Ramirez, Morcuende, Estévez, & Cava López, 2005).

In developed Western countries, people’s eating habits are currently characterised by an excess intake of calories and saturated fatty acids (SFAs). Diet with this type of fatty acid consumption have been linked to many diseases common in developed countries, such as obesity and coronary heart disease (Mata et al., 2002, Mellema, 2003, Ramírez and Cava, 2005). Consequently, there has been a growing movement over the last decade to reduce the fat content of deep fried products (Altunakar et al., 2004, Mellema, 2003, Salvador et al., 2005). According to the recommendations of scientific authorities and nutritional organisations including the World Health Organisation (WHO, 2003), dietary fat intake should ideally account for between 15% and 30% of total diet energy, and no more than 10% of caloric intake should be from SFAs. Additionally, it was also recommended that polyunsaturated fatty acids (PUFAs), which may help prevent coronary heart disease, hypertension, type 2 diabetes and cancer (Haak et al., 2007, Weber et al., 2008), should represent 6–10% (n-6, 5-8%; n-3, 1–2%) of total diet energy, where around 10–15% should be from monounsaturated fatty acids (MUFAs). Additionally, health agencies and professional organisations have issued recommendations to reduce the n-6/n-3 PUFA ratio of the diet (Garg et al., 2006, Simopoulos et al., 1999, WHO, 2003). This n-6/n-3 ratio is strongly correlated with mortality caused by cancer and cardiovascular, inflammatory and autoimmune diseases (Hoz, D'Arrigo, Cambero, & Ordóñez, 2004), and it was reported that the greatest risk factor for arteriosclerosis and ischemic heart disease is not hypercholesterolemia or high cholesterol intake but a high n-6/n-3 PUFA ratio (Okuyama & Ikemoto, 1999). In most industrial western societies, this ratio is currently about 15–20:1 (Simopoulos, 2002), whereas nutritional experts recommend an n-6/n-3 ratio of less than 4:1 (Valencia, Ansorena, & Astiasarán, 2006).

It was reported that it is possible to improve health status and well-being to reduce the risk of disease through modifications in one’s diet and/or dietary components (Jiménez-Colmenero, 2007). In this sense, nutritional authorities have persistently recommended a reduction in dietary saturated fatty acids and an increase in dietary MUFAs and PUFAs by increasing the consumption of foods rich MUFAs and PUFAs. Nevertheless, the unwillingness of consumers to change dietary habits suggests that in order to facilitate changes in eating habits, it is necessary to establish recommendations for cooking the most common foods (such as breaded frozen foods) using methods that will help consumers adhere to the nutritional recommendations.

The aims of the present work were to evaluate how the type of culinary fat used for pre-frying and the cooking method (baking and deep frying in olive or sunflower oil) affects the proximate composition and fatty acid profiles of two different breaded frozen foods and to determinate which cooking method will better influence the final proximate compositions and fatty acid profiles of cooked foods.

Section snippets

Sample collection and cooking procedures

Pre-cooked, frozen and breaded fish-based (tuna pasties) and meat-based (ham nuggets) foods from three different fabrication lots were elaborated by a local industry (Clavo congelados, Pontevedra, Spain).

In the case of tuna pasties, breading (50% of total weight) was prepared with margarine, salt, sugar, wheat meal and water, while content (50% of total weight) was prepared with egg white, pepper, onion, salt, sugar, sunflower oil, tomato, tuna, water, wheat meal, citric acid (E-330) and sodium

Results and discussion

The compositions of tuna pasties and ham nuggets, as well as the changes during pre-frying and cooking processes, are shown in Table 1 (tuna pasties) and Table 2 (ham nuggets). In both cases, moisture significantly decreased during the pre-frying process with respect to raw products. After pre-frying, no significant decrease in moisture content was found during cooking in the oven. There was a significant moisture content decrease in all fried products except tuna pasties pre-fried in sunflower

Conclusions

The fatty acid compositions of the tested products tended to become similar to that of the culinary fat used in frying, suggesting that the influence of culinary fat is more important in the final composition of the cooked product than the raw product composition or than the pre-frying fat. Frying in sunflower oil increased the PUFA proportion in the tested products but had negative effects, especially on the n-6/n-3 ratio. Frying products in olive oil had more beneficial effects than frying in

Acknowledgements

The authors wish to thank Xunta de Galicia for financial support (project PGIDIT05TAL003E). The authors also thank Carmen Carreira for her expert technical assistance.

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