AN ASSESSMENT OF FAT SUBSTITUTION WITH BUCKWHEAT SEED PREPARATION ON THE QUALITY OF COMMINUTED MEAT PRODUCTS

Zbigniew J. Dolatowski, Małgorzata Karwowska
Department of Meat Technology and Food Quality, Agricultural University of Lublin, Poland

ABSTRACT

Research has been conducted to determine the effect of fat substitution with buckwheat preparation on colour and lipid stability during 30 days of storage at 4°C in aspect of preparation usefulness as fat replacement in comminuted meat products. The results indicate the influence of fat substitution with buckwheat preparation on the colour changes of comminuted meat products as well as lipid oxidation. The reduction of fat level decreased the lightness and increased the redness, although yellowness was only slightly affected. During the storage of meat products slight changes of CIE L*a*b* parameters were noted. TBA values increased for all options after 10 days since the production but decreased for options with fat substitution with buckwheat preparations after 20 days since the production and increased for controls.

Key words: meat product, buckwheat, texture, colour.

INTRODUCTION

Consumer perception of the risks associated with a high fat intake (obesity, heart disease, etc) stimulates the development of food products with reduced fat content and/or altered fatty acid profiles [12, 13, 16]. Fat plays an important role in the quality of food, because it exerts an influence on texture and taste profile of meat products. Reducing the fat content, therefore, presents a number of difficulties in terms of flavour and texture. Low-fat meat products become firmer, more rubbery, less juicy, darker in colour compared to full-fat meat products [7, 13].

The production of low-fat meat products follows two main approaches: use of leaner raw materials or reduction of fat and calories by adding water and other ingredients with little or no calorie content. The reduction of fat levels in raw meat materials can be obtained through genetic and dietary modifications and/or through a number of physical techniques. Among non-meat additives used as fat substitutes in comminuted meat products are: carbohydrate-based (gums or hydrocolloids like carrageenans, alginates, starches) protein-based (soy, milk proteins, etc), and fat-based substances (structured lipids, sucrose polyesters). Each of the fat substitutes has different functional properties that provides both advantages and disadvantages for specific applications. However, little research has been done using buckwheat seed in low-fat meat products [9, 10, 11].

Buckwheat is a rich source of starch and contains many valuable compounds, such as antioxidative substances, trace elements and dietary fibre [6, 8]. Six flavonoids have been isolated and identified in buckwheat grain (rutin, quercetin, orientin, vitexin, isovitexin and isoorientin) [5, 19]. Buckwheat flavonoids may have many powerful medical functions. Rutin and other flavonoids show antioxidant activity, antagonize capillary fragility, decrease the permeability of the vessels and reduce risks of arteriosclerosis [1]. Thus, there have been a constant a great interest in increasing consumption of buckwheat-based products. However, even if the nutritional value of meat products can be improved, their quality must remain acceptable to the consumer.

The aim of this study has been to assess the effect of fat substitution with a buckwheat preparation on the colour changes of comminuted meat products as well as lipid oxidation (TBA value) and textural parameters.

MATERIALS AND METHODS

Meat products preparation
Experimental material consisted of finely comminuted meat products produced with varying degrees of fat replacement with buckwheat preparation. Fundamental materials used for manufacturing the test products were: cured lean beef – 60%, minced pork fat – 20%, ice water – 30% and buckwheat seed preparation, which replaced fat with the amount of 5, 15 and 20%. Luba buckwheat was treated in a hydrothermal way, being boiled in water and than dried in temperature 100°C until 15% moisture was obtained. After that dried buckwheat seeds were milled to powder. Powdered buckwheat was added to meat products. All ingredients were chopped in the following order: meat, ice water, buckwheat preparation and fat. Meat batters were heated in water (75°C) to an internal temperature of 70°C. After the completion of thermal processing, products were cooled in water to the temperature of 10°C, after which they were cold-stored at the temperature of 4°C. After overnight storage, all samples were analyzed for colour (CIE L*a*b*) and lipid oxidation (TBA value). All samples were stored for up to 30 days at 4°C.

Colour measurements
Hunter colour lightness, redness and yellowness (L*a*b*) values were measured on freshly cut surfaces of each sample using X-Rite reflection spectro-colorimeter, using illuminant D65 and 10° observer angle. The instrument was standardized using standard white plate (L*=95.87; a*=-0.49; b*2.39). Reflectance curves were determined from 360 to 740 nm. Readings were obtained from three locations of each products randomly selected to obtain a representative reading of the products colour.

Measurement of lipid oxidation
Lipid oxidation was measured by the 2-thiobarbituric acid method. The determination of thiobarbituric acid reactive substances (TBA) contained in the samples was performed according to Pikul et al. (1989) The rose-pink colour obtained through the reaction between malondialdehyde and 2-thiobarbituric acid was measured at 532 nm. The TBA content was expressed as mg of malondialdehyde per kg of the samples.

Instrumental evaluation of the texture
Instrumental texture profile analysis (TPA) was used to evaluate the instrumental texture using a texturometer TA XTplus (Stable Micro Systems, UK). From the resulting force-time curve the following parameters, which were related to texture, were deduced: hardness, elasticity and cohesiveness [2]. The speed during the test was 10 mm/min. and the level of compression was 50% of the original height of the sample. The pieces of meat products (20x20 mm) were used for the test. The same samples used for TPA test determinations were used for shear force determination. Samples were sheared using a texturometer TA XTplus equipped with a Warner-Bratzler shearing device with a cross-head speed of 60 mm/min.

Statistical analysis
Analyses were performed after 1, 10, 20, and 30 days of storage. Results were subjected to statistical analysis. The experimental design was intended to determine the influence of storage time and buckwheat seed preparation addition on the lipid oxidations and colour changes in comminuted meat products. The correlations between the level of fat substitution and all the parameters were calculated. Data was analyzed using a simple regression analysis. The experiment was carried out in three replications.

RESULTS AND DISCUSSION

The reflectance curves of samples are given in Fig. 1. All samples had reflectance minima at approximately 500 nm and maxima at approximately 550 nm. The increasing of fat substitution with the buckwheat preparation caused reflectance curves decreased. CIE L*a*b* parameters of meat products were slightly altered in comparison with the controls (Fig. 2, 3, 4).

The reduction of fat level slightly altered L* parameter values (lightness) during the whole period of storage (Fig. 2). The lightness of the meat products correlated with the level of fat substitution (Table 1); with the increase of the reduction of fat level, L* values decreased. The experimental meat products characterized the highest lightness values after 20 days since the production.

Statistical analysis indicated positive correlation between the reduction of fat level and a* parameter values. After the longer period of storage, lower correlation coefficient between the mentioned parameters were observed. The a* parameter values range from 3.56 for control sample after 10 days since the production to 5.51 for the sample with 10% fat substitution with buckwheat preparation at first day of chilling storage. No correlation between the reduction of fat level and b* parameter values was observed for meat products during the whole period of chilling storage (Table 1).

The changes of TBA values (Fig. 5) depended on the level of fat substitution with buckwheat preparation and time of storage. At the beginning of storage period (after 10 days) TBA values increased for all experimental products. After 20 days since the production, the mentioned parameter increased for the control sample; for the meat products with buckwheat preparation addition, TBA values decreased, average 0.70 mg malondialdehyde/kg meat products. Slightly differences in TBA values for the samples after 30 days of storage compared to the samples after 20 days since the production were noted. The minus correlation coefficient between the level of fat substitution and TBA values mean that with the increase the level of fat substitution with buckwheat preparation, the stability of lipids increased (Table 1).

The texture parameters evaluation of meat products showed that the reduction of fat level slightly altered texture parameters values (Table 2). The hardness I and II ranged from respectively 20.26 N and 18.10 N for the control sample to 24.34 N and 22.43 N for the sample with 5% fat substitution with buckwheat preparation. The cohesiveness and elasticity values were similar for all experimental meat samples. The analysis of correlation between the level of fat reduction and texture parameters (Table 3) indicated no correlation between the mentioned parameters.

The results obtained by Dolatowski et al. (2005) concerning buckwheat extrudate addition as a fat replacement showed that with the increase the level of fat substitution with buckwheat extrudate hardness decreased. It means that, from the technological point of view, buckwheat preparation, which was used during the present studies, is the better fat replacer.

CONCLUSION

The fat replacement with buckwheat preparation altered colour parameters of meat products (ligtness, redness, yellowness). The minus correlations between the level of fat substitution and L* parameter values that were obtained, mean that with the reduction of fat level the lightness decreased.

At the beginning of the storage period, slightly relationship between the level of fat substitution and TBA values was noted. After the longer period of storage, the high minus correlation coefficient that was noted mean that with the increase of fat substitution with buckwheat preparation the colour stability increased.

No correlation between the level of fat substitution and texture parameters of comminuted meat products was noted. It hint that it is possible to obtain the meat products with 20% fat substitution with buckwheat preparation that characterized similar textural parameters compared to the control product.

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Accepted for print: 11.12.2006

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