Zanardi E.*, Novelli E.**, Campaninni G.*, Madarena G.*, Chizzolini R.*
* Istituto di Scienza e Tecnologia degli Alimenti, Facoltà di Medicina Veterinaria, Università degli Studi di Parma, via del Taglio 8, 43100 Parma, Italy.
** Istituto di Patologia e Igiene Veterinaria, Facoltà di Medicina Veterinaria, Università degli Studi di Padova, Agripolis, 35020 Legnaro, Padova, Italy.
Mortadella is a finely minced cooked pork product obtained from lean cuts, such as shoulders and trimmings, mixed with emulsified fat, fat cubes obtained from the subcutaneous layer of the cheek and the neck (streaky bacon) and other additives. With the name of Mortadella Bologna it has been recognised as a D.O.P. product and it has been defined in a standard regulation (UNI, 1996).
Its fat content ranges from 25% to 30% according to type and quality level. With such a fat content it has raised the concerns of nutritionally minded consumers and, therefore, the interest towards changes in composition, and the possible adaptations in production technology, has increased in latest years.
As mentioned in a previous paper dealing with fat reduction in salame Milano (Zanardi et al., 1998a), according to international medical institutions dietary fat intake should be controlled both as quantity of calories and as type of fatty acids introduced. Nutritional guidelines suggest that dietary fat should provide between 15 and 30% of total calories and that saturated fats should be limited between 0 and 10% of caloric intake (WHO, 1990). Limitation in fat intake is thought to play a preventive role against various chronic disorders, such as obesity and coronary heart diseases, and some types of cancers (Flatt, 1993; Reddy, 1995).
Fat imparts a wide range of characteristics to foods, including desirable appearance, flavour, aroma, texture and mouthfeel and, therefore, reducing fat is not simply a matter of using less of it in the formulation. 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 first choice depends on the availability of suitable raw materials in term of composition and functionality. The reduction of fat levels in meat raw materials can be obtained through genetic and dietary modifications and/or through a number of physical techniques. Most of the currently available fat substitutes can be divided in three categories: protein-based (soy, surimi, dairy proteins, gluten, etc), carbohydrate-based (gums or hydrocolloids like carrageenans, alginates, starches, dextrins, cellulose derivatives) and fat-based substances (structured lipids, sucrose polyesters). Each of the fat mimetics has different functional properties that provide both advantages and limitations for specific applications.
On the lines of the previous study on salame Milano (Zanardi et al., 1998a), an investigation has been planned to test the possibility of producing mortadella with a fat content of about half the level of standard products. Mortadella can be considered representative of minced cooked ready to eat pork foods, e.g. frankfurter-type products, both as fat content and as production technology. For all of them the main problem is to maintain their typical quality attributes, otherwise low-fat items will not be accepted by the consumers.
The study included the measurement of peroxide number, TBARs and cholesterol oxidation products, due to the importance presently attributed to lipid oxidation for quality and human health reasons.
The technology that has been adopted to produce the different batches of mortadella has been described by Novelli et al. (1998). In detail, mortadella of normal fat content was produced in batches of 100kg each by mincing deboned shoulders (40%), porcine stomachs (25%) and 10% of fat emulsion (ice/fat/caseinate, 5/5/1). The minced raw materials were mixed with lard cubes from the streaky bacon (25%), salt (2.15 %), saccarose (1.28%), sodium caseinate (1.00%), polyphosphates (0.3%), sodium nitrite 50% in NaCl (0.2%), sodium ascorbate (0.1%), black pepper (0.1%), white pepper (0.04%), garlic (0.03%), nutmeg (0.02%) and macis (0.025%). The final batter was stuffed in 15cm diameter artificial casings (Viscosa) (15kg approximately per piece). Cooking took place in dry owens, set at 85°C, up to 72 °C core temperature and was followed by cooling under water sprays and refrigeration in cold rooms at 4 °C. Such a recipe was considered as representative of standard production for mortadella with a fat content of about 25%.
The recipe of a standard product was modified in various ways to test the possibility of different substances to reduce fat content below 20% and down to about 15%.
Standard lard cubes quota (i.e. 25%) was reduced to values ranging from 15% to 10%. The aim was that of preserving as much as possible the traditional aspect of cut surfaces while, at the same time, reducing the total amount of fat present. In such a way, though, fat content could only be reduced of a maximum value of about 5% since lard cubes provide approximately 10% fat to the final product.
A bigger amount of fat comes from the fat emulsion and the fat carried by shoulders. This type of fat, dispersed in the batter, was reduced by using ham trimmings as lean cuts instead of shoulders and by eliminating the fat emulsion. Ham trimmings were cleaned from visible fat and used in combination with porcine stomachs (rich in connective tissue and with a fat content of about 1%). Since the formulations based on ham trimmings and porcine stomachs tended to be paler than average, pig tongue was introduced in two formulations to improve the colour due to its high pigment content. In other formulations sandal wood extract was added to the batter for the same purpose.
Fat substitutes, such as gelatinised rind, carrageenans (Sanofi, RP 15), starch (Tipiak, Tapiocaline CR 521), soya (Protein Technology International 545) and milk proteins, were used in various percentages in the formulations to improve the organoleptic quality of low fat mortadella.
Low fat formulations were mixed with the same additives and cooked to the same core temperature as the standard formulation. The only difference has been the introduction of sandal wood extract as mentioned above. The general plan of the formulations is presented in Table 1.
All types of mortadella were subjected to standard analyses, such as chemical composition, NaCl, pH, colour measurement (Chizzolini et al., 1996), lipid oxidation (peroxide value, TBARS, cholesterol oxides) (Zanardi et al., 1998b) and sensory evaluation (Table 2).
The trials for low fat mortadella were based on a standard formulation that was kept as a reference point especially for sensory quality parameters. The tests aimed not only at reducing fat content but were planned also to evaluate the possibility of producing formulations which could maintain the commercial name of mortadella. Only in some formulations, therefore, unconventional ingredients were tested. In two cases (formulations 2 and 5), the tongue has been employed to test its ability to improve the colour of experimental mortadella. Caseinate was introduced in some formulations (2, 4, 5 and 6) for its emulsifying and water binding properties. Of the various trials carried out those which gave acceptable products are reported in Table 3.
The formulations 2, 3 and 4 have been based on the use of lean trimmings of fresh hams as partial substitute for shoulders, the latter having a fat content around 15% compared with about 5% of the former. A significant amount of gelatin emulsion obtained from rind was also employed to preserve the smoothness and the right level of cohesiveness and firmness of good quality mortadella that could be impaired by the decrease of fat content.
With such formulations it has been possible to produce technologically viable mortadella with a fat content ranging from 16.58% to 19.41%, without employing ingredients not allowed in normal products. In formulations 2 and 4 (with sodium caseinate) water content was above 60% and, correspondingly, protein and fat content were lower than in formulation 3. Sodium chloride was also higher in formulation 3 whereas the pH value was lower. All three formulations had pH values significantly lower than standard formulation 1.
Compositional changes had some effects on colour measurements (Table 4). Formulation 4 (sodium caseinate without tongue) had the highest L* values (of all formulations reported), the lowest a* and highest b* values (among formulations 2, 3 and 4). Consequently in the same formulation, Saturation was lowest of all seven formulations and Hue higher than formulations 1, 2 and 3. The results clearly indicate that the colour was light and had a yellow/brown shade. Sensory evaluations confirmed such measurements as can be seen from Table 5. Formulation 4 had the highest brightness and the lowest colour scores. Formulation 2 had a colour score higher than formulation 1, a proof that the use of tongue had positive effects on such a quality parameter. The presence of sandal wood extract, instead, did not appear to be sufficient to improve colour scores.
Sensory evaluations of formulations 2, 3 and 4 did not show many other significant differences among such formulations, neither did they differ significantly for important parameters from formulation 1. Some of these deserve mentioning. Small holes increased, fat smears, firmness and flavour decreased in formulation 4 (sodium caseinate without tongue). Overall acceptability was lower in formulation 2, probably due to low flavour scores.
The formulations 5, 6 and 7 represent the trials aimed at testing new ingredients and the possibility of lowering fat content below 15%. Such formulations, therefore, besides milk proteins, made use of carrageenans, starch and soya proteins. Ham trimmings were left out as other fat-less protein based ingredients were used.
Compositional data varied among the three formulations 6, 7 and 8. Water content was lower in formulation 6 in which the highest amount of starch had been used. The lowest fat content (13.84%) was found in formulation 7 in which gelatin emulsion, skimmed milk, starch and soya proteins had been introduced. Sodium chloride values were above 3% in all three formulations and higher than any of the previous four formulations. Colour measurements (Table 4) have shown that L* values were lower than those of formulations 1-4, especially in the case of formulations 6 and 7. The lowest a* and highest b* values have been found in formulations 7 and 6, saturation and hue were high because of the high b*, a clear indication of a colour of a yellow/brown type. Both such formulations had been added with sandal wood extract but not with tongue. Formulation 5 (with tongue), on the other hand, had colour parameters (a*, b*, saturation and hue) very similar to those of formulation 1.
Sensory evaluations of formulations 5, 6 and 7 pointed out, in particular, the high levels of small holes in formulation 7, the lower levels of smoothness in all three formulations compared with the other four ones and problems of flavour in formulations 6 and 7. The peculiar characters of formulation 6 were the high scores for flavour and objectionable flavour, probably a consequence of the use of high doses of starch and soya proteins. As a result, the acceptability came out to be rather low. Formulation 7 has been the leanest among the formulations tested. The addition of gelatin emulsion and the lower amount of starch were probably the reason for better scores for flavour and objectionable flavour but acceptability was not optimal.
Lipid oxidation measurements were carried out to verify that new ingredients would not, at least, have negative effects on lipid stability. Peroxide and TBARS values of low-fat formulations (Table 6) were rather variable but the range of the data obtained was in line with the results previously reported in commercial full fat samples or other types produced for experimental reasons (Ghiretti et al., 1997; Novelli et al., 1998).
Similar considerations can be made for cholesterol oxidation products (Table 7). The only oxide observed in all samples was 7-ketocholesterol, 25-hydroxycholesterol has been found in just one sample, 5,6a-epoxycholesterol was observed in two samples and the remaining oxides (7b-hydroxycholesterol and 20a-hydroxycholesterol) in about half the samples. The maximum value observed has been 6.77 m g/g of 7b-hydroxycholesterol in formulation 4. Total cholesterol oxidation was below 0.2% in all samples but one, and only in formulation 4 such parameter reached a value near 1%. The range of cholesterol oxidation was in line with the results obtained in other investigations both of mortadella and of other fresh and processed meats (Ghiretti et al., 1997; Novelli et al., 1998; Zanardi et al., 1998b; Zanardi et al., 1999).
Total cholesterol content varied from a minimum of 98mg/100g (formulation 6) to a maximum of 134mg/100g (formulation 5). The formulations with the lowest cholesterol content were number 2 and 6 followed by formulation 7, those in which pig stomachs content was 20% compared with a standard value of 25%. Such an ingredient has high cholesterol content (about 140mg/100g) compared with the tongue (about 87mg/100g), the backfat (about 54mg/100g), the streaky bacon (about 60mg/100g) and pork lean (between 50 and 60mg/100g) (Chizzolini et al., 1999).
In conclusion, the technological feasibility of producing mortadella with a low fat content has been proved. Most formulations were found to be acceptable at the sensory evaluation, but some characters, like colour or flavour, appeared to specifically need attention to avoid falling below normal levels.
Key words: mortadella, low-fat, quality, technology.
Parole chiave: mortadella, riduzione grasso, qualità, tecnologia.
SUMMARY - An investigation has been conducted to test the feasibility of producing mortadella with a low fat content. The research has shown that it is possibile to produce mortadella with a fat content down to about 16% without using substances not normally employed for such a cooked pork product. With the help of fat substitutes, such as milk proteins, carrageenans and soya proteins, a fat content just lower than 14% has been obtained. Quality characteristics, for instance colour and flavour, were negatively affected in some cases but, overall, it appeared that satisfactory formulations can be made. The determination of peroxide value, TBARS and cholesterol oxides has shown that there is no oxidation risk.
RIASSUNTO - È stata studiata la possibilità di produrre mortadelle a basso contenuto di grasso sia variando la quantità relativa di ingredienti normalmente utilizzati sia introducendo nelle formulazioni materie prime non convenzionali. Le prove fatte hanno dimostrato che è possibile raggiungere un contenuto di grasso di circa il 16% senza utilizzare ingredienti non consentiti nella produzione della mortadella. Una ulteriore riduzione, fino a poco meno del 14% è possibile con l’uso di proteine del latte, della soia e polisaccaridi gelificanti (carragenine). Le caratteristiche organolettiche in alcuni casi hanno presentato delle carenze, specie per quanto concerne il colore e l’aroma, ma in generale i risultati possono essere considerati soddisfacenti. Le misure relative alla ossidazione dei lipidi hanno dimostrato che non vi sono problemi in questo ambito.
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