Tadeusz Karamucki

The influence of myoglobin on the colour of minced pork loin

The influence of the total and chromatic absorbance at wavelengths of 525 nm (A525 and A525p) and 700nm (A700), and the relative content of oxymyoglobin (MbO2), metmyoglobin (MetMb) and deoxymyoglobin (Mb), on the value of the colour parameters (L*, a*, b*, C* and h°) of minced pork loin, were evaluated. Lightness (L*) depended almost entirely on variation in total absorbance at a wavelength of 525 nm. Redness (a*) depended on the forms of myoglobin and A525p, while yellowness (b*) depended mainly on the proportions of the reduced form (Mb), the oxygenated form (MbO2) and the oxidised form (MetMb). Yellowness (b*) significantly increased with a decrease in the relative amount of Mb and an increase in relative amounts of MbO2 and MetMb, although a greater impact was exerted by fluctuations in MbO2 than MetMb. Variability of chroma (C*) depended mainly on proportions of the forms of myoglobin. Hue angle (h°) depended primarily on chromatic absorbance at 525 nm (A525p).

The effects of blast chilling on pork quality.

The aim of this study was to determine the effects of blast chilling of pig carcasses on the physiochemical and sensory properties of the longissimus lumborum muscle. To this end, right half-carcasses were blast-chilled for 70min at -24°C and then for 22h and 50min at 1°C, while left half-carcasses were chilled conventionally at 1°C for 24h. At 2h and 6h post mortem, blast chilling had significantly reduced the temperature of the carcasses, as well as the rate of pH decrease and the rate of increase in EC. It had no significant effect on the ultimate pH or its range, or on EC at 24h post mortem, but it significantly lowered L*, b*, C* and drip loss compared to the conventionally chilled carcasses. Blast chilling adversely affected sensory characteristics such as tenderness and flavor. There were no significant differences between the effects of blast and conventional chilling systems on meat quality between conformation classes.

The relationship between colour and pH in cold - stored quail breast muscle

Abstract The purpose of this study was to analyse the colour of the breast muscles of Japanese Pharaoh quail on the first day after slaughter and again after further six days of cold storage, in relation to their muscle pH. The material for the study consisted of 40 breast muscles taken from the carcasses of six-week-old Japanese Pharaoh quail. Based on pH results, the muscles were divided into three groups: I (pH = 5.51-5.70), II (pH = 5.71-5.90) and III (pH = 5.91-6.10). After this the muscles were stored for a further 6 days at 4°C. It was found that the pH of freshly dissected quail breast muscle is a good indicator of the colour stability of muscles cold-stored at 4°C for six days. The lowest degree of colour stability was observed in the pH range 5.51-5.70. In the sensory evaluation muscles displaying this degree of colour instability were considered unacceptable or barely acceptable. In contrast, muscles in the pH ranges 5.71-5.90 and 5.91-6.10 displayed a high degree of colour stability and were considered acceptable in the sensory evaluation. The colour changes that occurred during storage of the muscles were due to changes in the values of all of the colour parameters (L*, a*, b*, C* and hº); however, the greatest changes were found in the case of redness (a*) and the hue angle (hº). The changes were caused both by alterations in the amount of pigment reached by light, and by changes in the relative amounts of the chemical forms of myoglobin. Streszczenie Celem pracy była analiza kształtowania się barwy mięśni piersiowych przepiórek japońskich rasy faraon w pierwszym dniu po uboju oraz po 6 dniach przechowywania w warunkach chłodniczych w zależności od wartości pH. Materiał do badań stanowiło 40 mięśni piersiowych wypreparowanych z tuszek 6-tygodniowych przepiórek japońskich rasy faraon. Na podstawie wartości pH mięśnie podzielono na trzy grupy: I (pH = 5,51-5,70), II (pH = 5,71-5,90) i III (pH = 5,91-6,10). Stwierdzono, że wartość pH mięśni piersiowych przepiórek w pierwszym dniu po uboju jest dobrym wskaźnikiem trwałości barwy tych mięśni przechowywanych w warunkach chłodniczych w temperaturze 4ºC przez okres 6 dni. Najmniejszą trwałością barwy charakteryzowały się mięśnie o pH 5,51-5,70, których barwa ulega w tym czasie niekorzystnym zmianom, a po okresie przechowywania była nieakceptowana lub słabo akceptowana w ocenie sensorycznej. Barwa mięśni o pH 5,71-5,90 i 5,91-6,10 cechowała się natomiast dobrą trwałością i była akceptowana w ocenie sensorycznej. Zmiany barwy zachodzące w czasie przechowywania mięśni polegały na zmianie wartości wszystkich parametrów barwy (L*, a*, b*, C* i hº), przy czym największe zmiany stwierdzono w przypadku czerwoności (a*) i tonu barwy (hº). Były one wywołane zarówno zmianami w ilości barwników, do których dotarło światło, jak i we względnej ilości form chemicznych mioglobiny.

A comparison of two methods of determining colour change in the assessment of the quality of pork

BACKGROUND The colour of pork is one of the most important measures of meat quality. For the consumer, it is a sign of freshness, crucial for the decision to buy a product. The storage of meat results in constant col- our changes. Differences can be found in all colour parameters, especially chromatic ones, such as redness (a*) and hue angle (h°), as these changes are significantly correlated with a number of quality traits. Colour change can be determined not only by evaluating changes in colour parameters, but also by establishing the change in absorbance of specific wavelengths of light. The aim of this study was to compare the usefulness of these two methods of determining colour change: parameters measured on the CIELAB and CIELCh scales and colour change (%CC) determined based on the absorbance of selected wavelengths of light, i.e. 505, 540, 560, 580 and 630 nm. In this paper, we analysed two methods of measuring colour change in terms of their relevance for meat quality assessment. METHODS The study involved 150 samples of the longissimus lumborum muscle collected from 150 carcasses of pigs slaughtered on an industrial line, weighing 65-107 kg, with an average carcass weight of 86.1 kg. Meat sensory analysis (colour, wateriness, firmness), physicochemical assessment (colour, WHC, pH48) and proximate analysis (moisture, total protein, fat, ash) were carried out. The methods included the determination of (I) changes in colour parameters measured on the CIELAB and CIELCh scales, and (II) colour change (%CC) based on the absorbance of selected wavelengths: 505, 540, 560, 580 and 630 nm. Chromatic absorbance values of a wavelength of 525 nm (A525p) and the relative content of Mb, MbO2 and MetMb were calculated according to the method proposed by Krzywicki (1979). RESULTS Basic chemical composition - with few exceptions - was not significantly correlated with differenc- es in the values of colour parameters (ΔL*, ?a*, ?b*, ΔC*, Δh°) and colour change (%CC). With an increase in scores in the sensory evaluation of colour, wateriness, and firmness, and an increase in WHC and pH48, the differences in lightness (ΔL*) significantly increased and differences in chromatic value (?a*, ?b*, ΔC*, Δh°) and %CC decreased, for all tested combinations of wavelengths. The highest correlation coefficients were observed for ?a* and Δh° and %CC540/630 and %CC580/630, with colour change (%CC540/630 and %CC580/630) showing a stronger correlation with the tested meat quality traits than the differences in redness (?a*) and hue angle (Δh°). We found a very strong correlation between changes in the relative levels of MetMb (ΔMetMb) and colour change (%CC) based on the absorbance of wavelengths of 540 and 505 nm, and 580 and 505 nm (r = 0.950*** and r = 0.967***, respectively). CONCLUSIONS The determination of colour change based on the absorbance of two combinations of wave- lengths, i.e. (I) 540 and 630, and (II) 580 nm and 630 nm, is more useful in the assessment of pork quality than changes in two most relevant parameters of the CIELAB and CIELCh scales, i.e. redness (Δa*) and hue angle (Δh°). Moreover, the determination of absorbance of a wavelength of 630 nm was more useful for determin- ing colour change (%CC) than 505 nm. Colour change (%CC) based on the absorbance of wavelengths of 540 and 505 nm and 580 and 505 nm reflect the changes in the relative amounts of MetMb very well.