Andrew Gigiel

The ultra rapid chilling of pork

Pork carcasses and sides were ultra rapidly chilled in air at -30°C and 1 m/s for 4 h and compared with controls chilled in air at 0°C and 0·5 m/s for 24 h. All the required heat was removed during the 4-h process, there was a 1% saving in evaporative weight loss, the pork could be cut and packed immediately and there were no important differences in appearance and bacteriological quality. The loin from sides, but not carcasses, froze during chilling and showed a fourfold increase in drip loss. Loins from both sides and carcasses were tougher than the controls.

Electrical stimulation and ultra-rapid chilling of pork

Six pigs were stimulated at 5 min post mortem and six remained unstimulated. All the pigs were split hot and one side from each pig was rapidly chilled in two stages (air at -40°C and 1 m/s for 80 min followed by 0°C and 0·5 m/s for 130 min) and the other side was conventionally chilled (air at 0°C and 1 m/s for 24 h). The weight loss from rapidly chilled sides was approximately 1% less than that from conventionally chilled controls. Cooked samples of Longissimus dorsi were tougher from unstimulated rapidly chilled sides (0·23 J) than from unstimulated conventionally chilled sides (0·18 J), whilst samples from both stimulated treatments were significantly more tender (0·15 J). These differences in toughness are thought to be due to a combination of cold shortening and lack of conditioning. The average pH in the longissimus dorsi of both rapidly and conventionally chilled stimulated sides at 50 min post mortem was 5·57 and samples from these muscles were slightly paler and more watery than the unstimulated controls.

Alternative methods of pig chilling.

Comparisons were made of the effect on cooling rate, weight loss, texture, bacterial numbers, drip and appearance of pork sides (average dead weight 75 kg) in refrigeration systems using high humidity (ice bank) or conventional chilling, both with and without a rapid pre-chill or delayed chilling, with and without a water spray. All treatments took between 15·7 and 19h post mortem to cool the deep leg of sides to 7°C. Weight loss varied between 0·95% for sides in the delay and spray treatment to 2·17% for conventional chilling. The texture of the M. longissimus dorsi of sides from the rapid pre-chill and conventional chilling treatment was significantly tougher than from the other methods, including those from the rapid pre-chill and high humidity system. Variation in texture between animals within treatments was far greater than between treatments, and could not be explained by variations in cooling and glycolytic rate. There were no significant differences (P > 0·05) in bacterial numbers, drip and appearance between treatments. The choice of chilling system can be made on the basis of weight loss and capital and running costs. The delay and spray treatment would save £37 800 on an annual throughout of 3 080 tonnes of pork compared with a conventional system.

Immersion chilling of hot cut, vacuum packed pork primals.

Hot-cutting and immersion chilling of pork was compared with a conventional air chilling process. The right sides of eight pig carcasses were cut into primals whilst hot, vacuum packed and chilled in sodium chloride brine at 0°C, whilst the left sides were chilled conventionally in air at 0°C and 1 m/s, before being similarly cut and vacuum packed. The primals from both treatments were then stored in air at 0°C for either 24h or 15 days post mortem. The immersion process achieved an average saving in weight loss of 1·9% after both storage periods, and took between 2·5 and 3·5 h less than the conventional process to reduce meat temperatures to 7°C. It did, however, produce significantly tougher meat after 24 h, although not after 15 days. Sensory evaluation of odour and appearance suggested a reduced shelf-life and a darker meat coloration for immersion chilled pork.

Spray chilling of lamb carcasses

Two spray-chilling treatments were developed to improve appearance and reduce weight loss during lamb chilling. Rates of cooling and weight loss and meat quality were compared to conventionally chilled carcasses. The first treatment was an intermittent spray during the first 3 h of chilling. The second consisted of only two sprays at 2 h and 10 h post mortem. The conventional control was a two-stage process, with air at 10°C and 1 m/s up to 10 h post mortem, followed by air at 0°C and 1 m/s for a further 14 h. Both treatments significantly reduced weight loss at 24 h post mortem compared to conventional, from 2·20% to 0·86% and 1·20%, respectively. During a further 4 days storage, the savings were maintained, with weight losses being 3·97%, 2·97% and 3·19%, respectively. There were small (<1 h) but significantly reductions in the cooling times of spray-chilled loins and legs, attributed to sustained evaporative cooling of the continually wetted surfaces. No effects on texture or drip loss and only slight effects on surface lean and fat colour were found. Variation in texture between animals within treatments was far greater than between treatments and could not be accounted for by variations in cooling rates.

Practical investigations of two-stage bacon tempering

Abstract Bacon has to be tempered (part-frozen) before it can be sliced in a high-speed slicing operation. Traditionally the desired slicing temperature was achieved in a long single-stage process. Increasingly a two-stage process of heat removal followed by temperature equalisation is used to reduce processing time and weight loss. The objectives of the work described in this paper were: 1. To provide practical design data for a two-stage bacon-slicing operation. 2. To provide data that could be used in the development and verification of a model that would help optimise current and new tempering systems.

Textural effect of chilling hot Longissimus dorsi muscle with solid CO2

This paper covers the work carried out on the textural effects of chilling hot boned meat using solid carbon dioxide (CO(2)). The purpose was to measure the texture of beef Longissimus dorsi (LD) chilled in boxes with solid CO(2) and to compare this with conventionally chilled meat. The results showed that CO(2) chilled meat were tougher than the controls. Shear force (SF) and work done (WD) results indicated that 63% of the CO(2) chilled meat were above 50N compared to 32% of the controls, taste panel would judge this as slightly tough. 22% of the CO(2) chilled meat was SF>100N which overall would be judged as extremely tough as compared to 2% of the controls. The work also showed that the laser diffraction technique was unable to distinguish between active and passive shortening giving only an average or overall length for the area viewed.