Marita Ruusunen

Reducing sodium intake from meat products

Sodium intake exceeds the nutritional recommendations in many industrialized countries. Excessive intake of sodium has been linked to hypertension and consequently to increased risk of stroke and premature death from cardiovascular diseases. The main source of sodium in the diet is sodium chloride. It has been established that the consumption of more than 6g NaCl/day/person is associated with an age-increase in blood pressure. Therefore, it has been recommended that the total amount of dietary salt should be maintained at about 5-6g/day. Genetically salt susceptible individuals and hypertensives would particularly benefit from low-sodium diets, the salt content of which should range between 1 and 3g/day. In industrialized countries, meat products and meat meals at home and in catering comprise one of the major sources of sodium, in the form of sodium chloride. Sodium chloride affects the flavour, texture and shelf life of meat products. The salt intake derived from meat dishes can be lowered by, whenever possible, adding the salt, not during preparation, but at the table. In most cases, salt contents of over 2% can be markedly lowered without substantial sensory deterioration or technological problems causing economical losses. Salt contents down to 1.4% NaCl in cooked sausages and 1.75% in lean meat products are enough to produce a heat stable gel with acceptable perceived saltiness as well as firmness, water-binding and fat retention. A particular problem with low-salt meat products is, however, that not only the perceived saltiness, but also the intensity of the characteristic flavour decreases. Increased meat protein content (i.e. lean meat content) in meat products reduces perceived saltiness. The required salt content for acceptable gel strength depends on the formulation of the product. When phosphates are added or the fat content is high, lower salt additions provide a more stable gel than in non-phosphate and in low-fat products. Small differences in salt content at the 2% level do not have marked effects on shelf life of the products. By using salt mixtures, usually NaCl/KCl, the intake of sodium (NaCl) can be further reduced.

Combined effects of NaCl and raw meat pH on water-holding in cooked sausage with and without added phosphate

The intake of sodium in diets is of concern in many industrialized countries. Attempts have been made to lower sodium intake via meat products. The keeping quality, taste and water-holding/firmness of meat products have usually been impaired. The water-holding in cooked sausage was determined by a laboratory sausage method. Beef and pork with varying natural post-rigor pH-values (range: pork 5.50-6.12 and beef 5.60-6.48) were used as mixtures, and 0.5-2.5 % NaCl was used with or without added commercial sausage phosphate (2,5 g/kg determined as P(2)O(5)). The pH-values of raw batter increased to a level 0.0-0.7 units higher than the pH-values of the respective meat mixtures. The increase was higher in lower pH-values, with higher salt levels and with added phosphate. The cooking caused an additional increase of about 0.0-0.2 units, and the increase was again higher at lower pH-values. Maximum in water-holding was reached in 2.5% NaCl in all pH-values, both with and without added phosphate. The pH-value of meat raw materials for the maximum water-holding was ca. 6.3. The combined effect of salt and pH is important in high salt contents and low pH-values. By 2.5% NaCl , where the maximum in water-holding was obtained, raw meat pH has the largest effect, but in low NaCl contents, below 1.0%, only a minor effect in pH-values below 5.9, and above that, almost no effect. Approximately the same water-holding as with 2.5% NaCl in pH 5.7 can be reached with 1.5% NaCl in pH 6.1 and above. The effects of the variables were similar with pork and beef. It was concluded that when lowering the salt content in cooked sausages, the pH of the batter should be increased by using high-pH meat mixtures and/or pH-raising phosphates in order to reach a high enough level of water-holding.

Reducing the sodium content in meat products: The effect of the formulation in low-sodium ground meat patties

This study investigated the effect of formulation on quality characteristics of low-sodium ground meat patties. The variation in sodium content was achieved by varying the NaCl content. The formulation variables studied were sodium and fat content and the use of phosphate. The patties were made using 50% or 60% meat in the formulations. Formulation affected the perceived saltiness of ground meat patties. Fat and lean meat content affected perceived saltiness, but their effects were opposite. When the fat content was increased the perceived saltiness increased, but when the meat content increased the perceived saltiness decreased. However, the effect of fat content on perceived saltiness was less than the effect of meat content. The use of phosphate effectively decreased cooking loss, particularly of high-fat-low-sodium patties. The same firmness could be reached with lower sodium content when phosphate was used.

Histochemical properties of fibre types in muscles of wild and domestic pigs and the effect of growth rate on muscle fibre properties.

This study reports the results of a comparison of the histochemical properties of various types of porcine muscles in wild and domestic pigs. In domestic pigs, the influence of growth rates on these properties were studied in five muscles: longissimus dorsi (LD), semimembranosus (SM), gluteus superficialis (GS), infra spinam (IS) and masseter (MAS). The growth rate was expressed as: (i) live weight (LW) at 165±2 days and (ii) daily LW gain from day 88 to day 165 (DG) on the experimental diet. LD, SM, GS and IS of wild pigs were found to contain a higher area percentage of oxidative type IIA fibres (type IIA%(area)) and a lower percentage area of glycolytic type IIB fibres (type IIB%(area)) than the same muscles of domestic pigs. The capillary density in the light muscles (LD, SM, GS) of wild pigs was twice that of domestic pigs, indicating higher oxidative capacity. In domestic pigs the cross sectional area of type IIB fibres (CSA(IIB)) was markedly larger than the cross sectional area of type I (CSA(I)) and IIA (CSA(IIA)) fibres. The average fibre cross sectional area (CSA(fibre)) was about the same in the muscles of wild and domestic pigs except in LD and SM, where the average fibre cross sectional area was approximately 25% smaller in wild pigs than in domestic pigs. This difference was caused by the large cross sectional area of type IIB fibres in the light muscles of domestic pigs. In the light muscles of domestic pigs, the cross sectional area of type IIA fibres increased most with increasing growth rate. Growth rate influences muscle fibre properties only in light muscles, not in dark muscles.

Bovine muscle glycogen concentration in relation to finishing diet, slaughter and ultimate pH.

The aim of this study was to investigate the effects of a high-energy diet provided for a rather short time prior to transportation to slaughter on muscle glycogen concentration on farm, after transportation and after refrigeration of the carcasses. The experiment involved 60 Ayrshire bulls which were fed either a low energy diet of 100% grass silage or a compound feed based diet providing 10.8 and 12.9 MJ of metabolizable energy per kg of dry matter, respectively. Identical setup of 30 bulls was carried out in spring and in summer. Three muscle samples were obtained from the longissimus dorsi and gluteus medius muscles: a biopsy prior to initiation of experimental feeding (B1); another biopsy after 14 days on diet (B2); a post mortem sample at 48 h after slaughter (3) (also M. semimembranosus). Initial resting muscle glycogen concentration affected the responsiveness of glycogen to diet. The more glycogen there was initially the less glycogen increased (r=-0.678, p<0.0001). However, compared to the low energy diet the high energy diet seemed to protect cattle from potentially glycogen-depleting stressors such as high temperatures and transportation. The cattle on high energy lost 7±4.0 (se) mmol/kg and 23±3.9 mmol/kg during transportation in spring (cool weather) and in summer (hot weather), respectively, whereas the cattle on low energy diet lost 16±3.8 mmol/kg in spring and 33±4.1 mmol/kg in summer. The overall protective effect of high energy diet corresponded to 0.65 pH units. The effects of diet were reflected all the way to ultimate pH values [5.69±0.03 (high energy); 5.93±0.03 (low energy)] (p<0.0001) and residual glycogen concentrations (p<0.0001). It seems indeed that providing a diet high in energy for a couple of weeks prior to transportation to slaughter is one of the many appropriate measures to take in the fight against bovine dark-cutting.

Physical and sensory properties of low-salt phosphate-free frankfurters composed with various ingredients

The physical properties and sensory attributes of phosphate-free frankfurters were examined using response surface methodology by varying the amounts of five compositional variables: salt, modified tapioca starch-, sodium citrate (NaC)- and wheat bran and fat in the batter. Altogether, 20 different types of frankfurters were prepared. When the frankfurters were made without phosphate, additional non-meat ingredients were needed at salt contents of less than 1.5%. Modified tapioca starch and sodium citrate decreased frying loss, with the former also improving water and fat binding.

Effect of sodium citrate, carboxymethyl cellulose and carrageenan levels on quality characteristics of low-salt and low-fat bologna type sausages

Quality characteristics of low-salt bologna-type sausage manufactured with sodium citrate (NAC), carboxymethyl cellulose (CMC) and carrageenan (CAR) were examined. Three levels of salt, NAC, CMC and CAR, and two levels of fat were used. Batter and sausage pH values were measured and the frying loss of sausages was analysed by frying slices in an electric grill. Firmness, juiciness, saltiness and flavour intensity of the sausages were sensorically evaluated. Altogether 20 separate sausage batches were prepared. In low-salt sausages containing less than 1.4% NaCl, the use of NAC, CAR and CMC decreased frying loss and increased saltiness. NAC and CAR also increased flavour intensity, but CMC did not. Furthermore, NAC, CAR and CMC increased the firmness of the low-salt sausage, while only NAC increased juiciness when the NaCl content was below 1.4%. NAC increases, however, the sodium content of the product. Therefore, it can be concluded that in low-salt sausages no additive alone is suitable. A mixture of NAC and CAR appears to be the best combination.

Some effects of residual glycogen concentration on the physical and sensory quality of normal pH beef.

The aim of this study was to assess the effects of residual glycogen concentration on the physical and sensory quality of normal-pH beef. Longissimus thoracis et lumborum muscles (n=42) having ultimate pH (48 h) between 5.50 and 5.75 were excised, assayed for residual glycogen concentration and divided into three categories according to the residual glycogen concentration. The categories were ⩽25 mmol/kg, 25.1-49.9 mmol/kg and ⩾ 50 mmol/kg. One half of every LTL muscle was aged for 28 days. All samples were evaluated for fresh meat colour, drip loss, shear force, thawing and frying losses and fried steak colour as well as sensory attributes of tenderness, juiciness, flavour and overall palatability. The independent significant effects of increasing residual glycogen concentration on the physical and sensory quality of normal-pH-beef were, although numerous, quite modest in magnitude. The water holding variables in the form of decreasing drip loss (p<0.061), increasing thawing loss (p<005), increasing sum of losses in thawing and frying (p<0.05), and decreasing sensory juiciness (p<0.05) were somewhat affected as were decreasing fresh meat redness (Minolta a*) (p<0.005), decreasing shear force (p<0.05) and increasing yellowness (Minolta b*) of the steak (p<0.0001). Beef of the lowest and highest glycogen category were the ones behaving slightly differently from each other, the intermediate category mostly followed the pattern of one or the other.

Comparison of histochemical properties of different pig breeds

The study involved 158 pigs: 51 Hampshire (H), 54 Landrace (L) and 53 Yorkshire (Y). The aim of the study was to compare muscle histochemical properties of M. longissimus dorsi and adductor between muscles from pigs of purebred Hampshire, Landrace and Yorkshire lineages. The following histochemical properties were determined: 1) the percentage of type I, IIA and IIB fibers in number (calculated on the basis of the number of different fiber types) and area (calculated on the basis of the area of different fiber types) as analyzed with the myosin ATPase method using an acid preincubation solution of pH 4.6; 2) the cross sectional area of each fiber type; 3) the percentage of oxidative fibers on the basis of the NADH-TR method; and 4) the capillary density of the muscles. The cross-sectional area of type IIB fibers was the largest in Landrace. The highest capillary density (capillaries per mm(2)), 254 ± 38, was in longissimus of Hampshire. A positive correlation between M. longissimus dorsi and M. adductor was found in the percentage of type I, IIA and IIB fibers in number and area, cross-sectional area of each fiber type, and capillary density. The differences in histochemical properties between breeds were, however, smaller in M. adductor than in longissimus dorsi muscle. In addition, the variation in muscle fiber composition in pigs within the breeds was larger than the average variation between the breeds.

Activity of porcine muscle glycogen debranching enzyme in relation to pH and temperature

The activity of glycogen debranching enzyme (GDE) was studied in relation to pH value and temperature in porcine masseter and longissimus dorsi muscles. A glycogen limit dextrin was used as the substrate for GDE, and the enzyme was derived from raw meat extracts. In both muscles, the pH only weakly affected the activity of GDE at the pH values found in carcasses post-slaughter. However, the activity of GDE decreased strongly (P<0.001) when the temperature decreased from values of 39 and 42 °C, found just after slaughter to values of 4 and 15 °C. In both muscles the activity of GDE began to fall at temperatures below 39 °C and was almost zero when the temperature decreased to below 15 °C. Thus, the activity of GDE may control the rate of glycogenolysis and glycolysis, but does not block rapid glycolysis and pH decrease when the temperature is high. This may be important in PSE meat, where the pH decreases rapidly at high temperatures, but rapid cooling could limit the activity of GDE and thus glycogenolysis. As expected, GDE was more active in the light longissimus dorsi muscle than in the dark masseter muscle.