Changes in the Quality Attributes of Selected Long-Life Food at Four Different Temperatures over Prolonged Storage

This study reports the development of selected indicators affecting changes in food quality and safety of selected long-life canned (Szeged goulash, canned chicken meat, pork pâté, canned tuna fish) and dehydrated (instant goulash soup) food during a two-year storage experiment at four different temperatures. The storage temperatures were selected to represent Arctic (−18 °C), temperate (5 °C), subtropical (25 °C) and tropical (40 °C) climatic zones where such food is likely to be stored during, for example, humanitarian and military missions. Microorganism amounts below the detection limit (p < 0.05), regardless of the storage temperature (p ≥ 0.05), were monitored in canned samples. The contents of dry matter, fat and proteins did not change during storage, regardless of the storage temperature (p ≥ 0.05). During the 24-month storage, all food showed an increase in the level of ammonia (p < 0.05) and the TBARS-value (p < 0.05), whereas the rate of increase in both parameters was significantly higher at higher storage temperatures (p < 0.05). The losses of individual amino acids during storage ranged from 5% rel. calculated on the amino acid contents in Month “0” up to 15% rel. (p < 0.05). With storage temperatures above the freezing point, the hardness values decreased with the increase in the storage temperature (p < 0.05) and prolongation of the storage period (p < 0.05). Moreover, with temperatures of −18 °C, the development of hardness, measured as the “decrease rate”, was significantly higher compared to the absolute values.

Research of milk fat oxidation processes during storage of butter pastes

Basic quality indicators studied: acidity, peroxide, anisidine value and integrated value of complete fat oxidation. Butter paste was selected as a reference, consisting of butter, skim milk powder and fat-soluble emulsifiers. Peroxide value during storage at the temperature of (4 ±2 °С) for the first 4 days did not exceed 5.0 1/2 О mmol.kg-1, on the 15th day fat peroxide value of butter paste with milk-vegetable protein exceeded permissible limits that is indicative of milk fat contamination. At the temperature of (-3 ±1 °С) butter paste fat couldn't be qualified as fresh when storing during 15 days, peroxide value exceeds permissible limits on the 25th day of storage. Rising of the peroxide value above 5 1/2 О mmol.kg-1 was detected on the 25th day of storage, exceeding of threshold value was on the 45th day. It was established that rate of oxidation processes in butter pastes with vegetable protein is the highest among all studied samples in each particular control and observation point. It was determined that the rate of secondary lipid oxidation depends on the storage temperature and is observed when storing butter paste samples at a temperature of (-3 ±1 °С) on the 10th day, (-24 ±2 °С) – on the 30th day of storage. Acid value did not exceed recommended limits (2.5 °K) and was on average – 2.3 °K when storing butter paste during 10 days at a temperature of (4 ±2 °С); 2.1 °K during 20 days at the temperature of (-3 ±1 °С), 2.4 °K during 40 days at the temperature of (-24 ±2 °С). In view of obtained results of fat phase stability evaluation of studied butter pastes, the following storage maximum time is recommended: at the temperature of (4 ±2 °С) ‒ 7 days, at the temperature of (-3 ±1 °С) – 15 days, at the temperature of (-26 ±2 °С) ‒ 30 days.

Modelling of the process of vybromechanical activation of plant raw material hydrolysis for pectin extraction

Centrifugal and vibrational technological effects are among the main approaches to intensify the process of plant raw materials hydrolysis for pectin extraction. With the impulse intensification of such a process, it is possible not only to increase its efficiency, but also to achieve the compactness of the equipment, reduce the cost of electricity and improve the quality of the product of hydrolysis. The hypothesis is confirmed, according to which the vibro-centrifugal intensification of hydrolysis increases the driving force of the process by not only activating the material flows of raw materials and reagents, but also by reducing the resistance in the technological environment. Graphical and analytical dependencies of the power and energy parameters of the oscillatory system were obtained, which proved the overcoming of the flow resistance of the liquid medium in the entire speed range of the drive shaft with the potential to intensify the process at a power consumption of 2.0 – 3.0 kW and or by the force of 2.3 – 2.5 kN using the Lagrange and Cauchy methods for composing and solving the equations of motion of the moving components of the tested hydrolyser with vibrating activators, and the methods of mathematical analysis and their processing in the MathCAD. The analysis of the presented parameters of the studied process of mixing the pectin-containing mass in the hydrolyser allowed us to determine the rational mode parameters of processing, which correspond to the angular velocity of the drive shaft  rad/s at the power consumption of 500 – 600 watts.

Substantiation of regime parameters of vibrating conveyor infrared dryers

The analysis of constructive-technological schemes of vibrating conveyor machines for heat-exchange processing of bulk technological masses in the current mode is carried out, which allowed to substantiate the effectiveness of using a new modification of infrared dryers of vibration-wave execution with a flexible transporting body. For this scheme, a vibrating system is developed which mathematical modelling allowed to determine and substantiate the main parameters of the operating mode of the drive mechanism of the projected device. The experiments, using the developed research model, confirm and refine the results of theoretical analysis, energy efficiency and comparatively low metal consumption of the design structure. The difficulty of working with such a large number of factors led to the application of the second similarity theorem and the introduction of a mathematical model of the criteria of Stanton, Froude, Burdo, whose magnitudes are reflected through the main factors of influence and were found experimentally. After using the "dimension theory" and graph-analytic analysis of power functions, a criterial equation of the investigated process was obtained. This allows recommending the regime parameters and the design series of projected thermo-radiation dryers with vibration-wave transport of products when varying the main factors of influence.

Effect of infrared radiation on chemical and physical properties on Duku’s peel

Infrared radiation has a potential for drying agricultural commodities such as the peel of duku. Drying of duku's peel in a whole duku using infrared radiation could become an effective method to eliminate the water on the peel but not in the flesh and could increase the shelf life of duku. The objective of this study was to investigate the potential of using infrared radiation for drying the peel of duku which would increase the shelf life of duku during storage. Duku's peel drying process was achieved by means of heating duku using a pairs of electric infrared emitters (IRE) facing each other with the emitter distance of 6 cm and 10 cm for a relatively short heating time of 50, 60, 70 and 80 seconds and after that stored at a cool room at the temperature of 15 °C for the length of one month. During storage, the physical and chemical changes of duku were then evaluated. It was found that the weight loss, fruit firmness, and total soluble solid of duku dried by means of exposing to Infra Red Emitter (IRE) were significantly affected by the distance of IRE, the temperature of IRE and the time exposed to IRE. However the titratable acidity only affected significantly by the distance of IRE. There were no significantly changes of browning index on duku during drying by exposing to IRE and while stored up to 25th day of storage. Drying duku by exposing it to IRE show a slightly better shelf life than the previous work.