EFFECT OF SODIUM CHLORIDE REDUCTION IN DRY PORK ON SENSORY QUALITY PARAMETERS AND INSTRUMENTALLY MEASURED COLOUR

The aim of this paper was to examine sensory properties and instrumentally measured colour of dry pork produced with less amount of sodium chloride. Trial was consisted from five batches, two control and three experimental. Pork from control group was cured with 6% nitrite curing salt (C1 group) and with 3% nitrite curing salt (C2 group), respectively. Pork from 1 experimental group was produced with 2% nitrite curing salt and 1% potassium chloride; pork from 2 experimental group was produced with 1,5% nitrite curing salt and 1,5% potassium chloride; dry meat from 3 experimental group was produced with 2% nitrite curing salt and 1% ammonium chloride. Curing process lasted for 7 days; smoking, drying and ripening for 21 days. In final products, water activity, moisture, protein and fat content was determined. Taste was best evaluated in dry pork from C2 group and worst in dry pork from 2 group. The most expressed saltiness was determined in dry pork from the first control group (C1) that corresponded to the largest amount of added salt. Due to most expressed bitter taste, the evaluation for overall acceptability for dry meat from the second experimental group was the lowest. The evaluation for overall acceptability of dry pork from the first control group was significantly lower in the comparison with the evaluations for dry meat from the second control group (C2) and the first experimental group (P ≤ 0.05).


Introduction
Due to several negative health influences of excessive dietary sodium intake, it is necessary to reduce salt/sodium content in food.Excessive sodium intake may cause hypertension that is one of the major risk for prevalence for cardio-vascular diseases and can lead to direct risk of heart attack (Perry and Beevers, 1992), hypertrophy of the left heart chamber (Schmieder and Messerli, 2000), sodium retention in extracellular fluid (MacGregor and de Wardener, 1997), greater possibility of infection by Helicobacter pylori and risk of gastric cancer (Tsugane et al., 2004), increase of urinary excretion of calcium and risk of forming of kidney calculi (Cappuccio et al., 2000), risk of reduced bone density (Devine et al., 1995), exacerbations of asthmatic seizures (Mickleborough et al., 2005) and increase of HOMA (homeostasis model assessment) insulin resistance in patients with essential hypertension (Kuroda et al., 1999).
Dietary sodium intake in many cases exceeds requirements recommended by World Health Organization.Sodium chloride (salt) content can be reduced in meat products in different ways but most common is partial replacement of sodium chloride with potassium chloride (Terell, 1983;Guàrdia et al., 2006).Besides potassium chloride, other chloride salts, mainly salts of magnesium and calcium and ascorbates can be used as replacers (Ruusunen and Puolanne, 2005).The main problem in this case is the occurrence of a bitter taste of product, because only sodium chloride has a clearly salty taste.
According to some literature data, the sodium content could be reduced in dry-cured pork loin down to 50% by using a mixture of potassium-chloride, magnesium-chloride and calcium-chloride without significantly affecting either the sensory and/or safety quality of the final product (Aliño et al., 2009;Armenteros et al., 2009).Sodium content could also be reduced in dry-cured ham by about 40% by similar mixture of chloride salts keeping similar physicochemical properties and low microbiological development (Blesa et al. 2008;Aliño et al., 2010).
Partial substitution of sodium-chloride with other chloride salts, Blesa et al. (2008) did not found out significant changes in microorganism count at different formulations of salts.
The aim of this paper was to examine the changes in sensory quality of dry pork caused by replacing of sodium chloride with potassium-chloride and ammonium chloride as well as instrumentally measured colour.

Dry pork production
Five groups of dry meat were produced.Pork (m.longissimus dorsi) was cured with nitrite curing salt in the different amount and with the mixtures of sodium-chloride and other chloride salts according to the Table 1.After curing for 7 days, smoking and drying lasted for 21 days in the smoking house under the environmentalconditions.

Instrumental colour determination
Colour of dry pork was evaluated using colorimeter (Minolta Chroma Meter RC-400).The CIE system color profile of lightness (L*), redness (a*) and yellowness (b*) was measured by reflectance colorimeter using illuminant source D65, 8-mm aperture and 10° observation angle (CIE, 1976)..The colorimeter was calibrated throughout the experiment using a standard white ceramic tile (Y = 87.2;x = 0.3173; y = 0.3348).Color was measured on three cut surface of dry pork at room temperature of 22°C, at samples temperature of 10°C and on each surface three measurements were carried out.

Sensory evaluation
Surface and cut colour, consistency, odour, taste and overall acceptability were assessed by a sensory panel.Numeric-descriptive scales with 5 points were used, whereas 5 is the best evaluation and 1 is the worst.Saltiness, hardness and bitter taste evaluated by 5 points system, whereas the 5 is the most expressed attribute and 1 is at least expressed attribute.Sensory evaluation was carried out by 6 trained assessors under the same conditions.

Results and discussion
The results of the instrumental determination of cut surface colour of products are presented in Table 2.In this study, lightness of samples of the first experimental group (37.97±2.18)was significantly higher (P ≤ 0.01) compared to lightness of dry meat from the first control group (33.10±3.24),from the second control group (34.44±0.10)and products from the second and third experimental group (34.52±1.93 and 32.44±2.41,respectively).Highly significant (P ≤ 0.01) differences was determined between redness of dry meat from the first control group (8.10±0.87)and from the second control group (9.47±0.80)as well as samples of third experimental group (9.25±0.37).No significant differences (p ˃ 0.05) were determined between yellowness for all examined group.
Results of sensory evaluation of dry pork are shown in tables 3, 4 and 5.
Regarding surface colour, cut colour and odour all groups recieved similar grades.The lowest grades for consistency received dry pork from the first control group (C1), significantly different from all other groups (P ≤ 0.05).It can be explained with the largest amount of salt used for the production of dry pork production in this group.Regarding to smaller amount of salt used in dry meat from other groups, consistency was evaluated as better and more desirable.Sensory evaluation for consistency was in relation with the hardness which was significantly higher (P ≤ 0.01) in dry pork from the first control group (C1) compare with dry meat from other groups.
The higher grade for taste received dry pork from the second control group (C2) and it was significantly different (P ≤ 0.05) in the relation to dry meat from the first control group (C1) and from the first and third group of dry meat.The lowest grade received product from the second experimental group and it was statistically different from dry meat from other groups (P ≤ 0.01).The lowest grade for taste for dry pork from this group is the result of bitter taste originated from potassium chloride that highly evaluated in the comparison with products from other groups (P ≤ 0.01).Bitternes was expressed in the highest level in dry pork from the first and from the third group and it was significantly different from the products from the first and the second control group (P ≤ 0.01).It was result of reducing sodium chloride content and adding of potassium chloride and ammonium chloride.
The most expressed saltiness was determined in dry pork from the first control group (C1) that corresponded to the largest amount of added salt (6%).It was statistically different from grades for dry meat from other groups (P ≤ 0.01).According to this finding, the evaluation for overall acceptability of dry pork from the first control group was significantly lower in the comparison with the evaluations for dry meat from the second control group (C2) and the first experimental group (P ≤ 0.05).Due to most expressed bitter taste, the evaluation for overall acceptability for dry meat from the second experimental group was statistically different from others (P ≤ 0.01).

Table 2 . Results of the instrumental determination of cut surface colour of dry pork, CIE Lab system
Numbers with different superscript letters are significantly different (P ≤ 0.01)