All conventional heat processing calculations are based on as few as two equations: a “primary” equation which corresponds to the first order kinetic of microbial inactivation represented by a log-linear survival curve, and a “secondary” equation which describes the effect of the heating temperature on the thermal resistance of target spores. Improvements of heat inactivation modelling consist in the extension of these equations into more general primary models which are able to fit typical non log-linear survival curves and multifactorial secondary models which take non only heating temperature, but also some new other environmental factors into account. A first models generation inputs only factors such as pH or water activity which are related to the heating phase regardless of recovery conditions. A second models generation further includes environmental factors linked to the recovery conditions of incubation for the calculation of heat resistance. These new trends lead to the main following consequences: i. the efficiency of a heat treatment is more suitably characterised by the bacterial inactivation ratio than by the traditional F-value which is no longer additive, ii. The lethality factor concept can be usefully extended to a more general function which would include not only heating temperature, but also main other environmental factors.
Today, Korean style dishes are being globalized, and with such a trend, it should be ensured that they can be safe from foodborne contamination. In this study, QRA, which is a quantitative technique to predict contamination levels and to perform sensitivity and scenario analyses, was performed in order to achieve better safety management for Korean style menu preparations. First, the hygienic conditions of Korean style dishes were surveyed, showing that these foods would not be safe if managed improperly. Saengchae, which was one of the dishes, proved vulnerable to pathogen contamination, and was selected for the case study. As a result, the hazard factor was determined as Staphylococcus aureus, and the hygienic conditions in the restaurant used for the case study were considered safe from food contamination. Through sensitivity analysis, the CCP in the preparation procedure was determined as the storage step. Through scenario analysis, the CL of the resultant CCP was estimated as a storage temperature lower than 15°C, when stored for 3-5 hours. In conclusion, we demonstrated that QRA, known as a versatile solution in quantitative analysis, can be applied successfully to aid conventional HACCP for the safety management of Korean style menu items. Therefore, this study provides an example of a quantitative approach for more extensive cases in the safety management of Korean style dishes.
This paper reviews recent developments on various aspects of food freezing. The various effects of freezing and frozen storage on food quality are described, including the role of glass transition. Methods for calculating freezing time and the evolution of temperature and phase change are reviewed and their underlying assumptions and limitations are critically examined. Finally, recent developments in freezing, thawing and freeze concentration techniques are reviewed: high pressure freezing and thawing, ultrasound assisted freezing, progressive freeze concentration, osmodehydrofreezing, immersion freezing in ice slurry, and the use of antifreeze proteins.
Thermal processing is a very common technique in the food industry. Commonly foods are overprocessed to ensure safety, but this may give excessive loss of quality attributes. Thermocouples are commonly used to obtain temperature-time profiles, but for many products it is not feasible to use them. Time-temperature indicators (TTIs) are small particles containing a reactive species that can be passed through a process and then assayed to measure the process effects. A series of tests have been carried out to determine the feasibility of using TTIs to validate thermal processes, using a pilot scale process vessel. TTI results could show the effects of local wall heating and distinguish between different heating regimes. Particle paths can be quantified using Positron-Emission Particle Tracking (PEPT) ; for viscous fluids of the kind found in food applications there is very close match between the flow of the fluid and of the TTI. Suggestions for the use of TTIs are made.
As a food-heating process, the Joule heating system has been receiving increasing attentions as a sophisticated heating system because of nonscorching, accurate heating, and cleanness. However, there are a few reports concerning the internal temperature distribution of food materials, especially in relation to the Joule heating system. In a previous paper, we developed a visualizing method to observe and record the internal temperature distribution of food materials and compared the visualized results with the data simulated by a numerical analysis. As the results, the visualized results accurately coincided with the data from the numerical analysis. However, in order to apply the Joule heating method to various foods, the experiment and numerical analysis must be discussed in the case of a change in the area of the electrode plates. In this paper, the measurement of the potential distribution and numerical analysis are proposed and the heat generation in the case of a change in the area of the electrode plates is clarified. The effectiveness of the proposed method is shown by comparing the experimental results with the analysis results.
Bowel sound (BS) is a biological audio signal stemming from peristaltic activity of intestines. We investigate the effects of a kind of foods on BS as the first attempt to develop a design method of custom-made foods by BS analysis. In this paper, a new procedure to detect BS by multidimensional signal processing is developed, leading to high detection accuracy of them, since an automatic BS detection system is absolutely required in order to process enormous quantities of BS data. The procedure, which involves our previous works, consists of independent component analysis, wavelet filtering, pattern matching in frequency domain, and threshold processing. In particular, using the new wavelet filter boosts the robustness and the new threshold processing decreases the miss detection ratio, compared to our previous works. Through a performance evaluation test of the new method, high detection ratio was achieved, which averaged 99%. Then, the false detection ratio was less than 2% and the additional detection ratio was more than 270%.
The effects of product inhibition on lactic acid fermentation from fresh cassava roots in tofu liquid waste by Streptococcus bovis were studied in batch culture. The lactic acid production and growth rate gradually decrease with increase of inhibitor (lactic acid) concentration. The effects of product inhibition on productivity and specific growth rate were confirmed by the Lineweaver-Burk plot to noncompetitive inhibition. The product inhibition was evaluated by two inhibitions constants: inhibition constant for productivity (Ki) and inhibition constant for specific growth rate (Ksi) . They decrease with increasing of inhibitor concentration. The values of Ki and Ksi in a rich media are smaller than those in a poor media and the Ki is larger than the Ksi in those media. The experiment results on batch fermentation agree with the noncompetitive inhibition model for about four days, but they deviate from the inhibition model after four days due to high inhibitor concentration. It is supposed that accumulation of lactic acid in broth decidedly causes damage on viable cell.
Deamidation of food proteins by cation-exchange resins is a promising method for modifying their functional properties without causing any peptide-bond hydrolysis. The gelation property and the water affinity of phytate-removed deamidated soybean globulin (PrDS) were evaluated in this study. Soybean globulin (US) was prepared by isoelectric precipitation, and phytate was removed by use of anion-exchange resins. Then, the phytate-removed soybean globulin (PrS) was deamidated by using cation-exchange resins of carboxylate type. The heat-induced gel property of PrDS was compared with that of PrS and US. The affinity of the soybean globulins for water was evaluated by the parameters obtained from pulsed NMR measurements. In addition, the denaturation temperature of the soybean globulins was determined with DSC. The water-retaining property of the heat-induced gel was better in the order of PrDS > PrS > US. From the pulsed NMR measurements, the amount of bound water in the untreated soybean globulin was almost constant irrespective of the water content. According to the correlation time of bound water τb obtained from pulsed NMR measurements, the affinity of soybean globulin for water was enhanced by deamidation, which was assumed to be the reason for the better water-retaining property of PrDS. However, the amount of bound water was decreased by phytate-removal and deamidation. DSC measurements showed that removal of phytate and deamidation made the denaturation temperature of soybean globulin slightly increase.
The mutagenicity of the extracts from defatted rice bran by water or subcritical water treatment at 50°C to 250°C was examined using the Umulac AT test, which is a kit reagent for assaying the genotoxin-induced umu gene expression. The examination revealed that the extract at any temperature was negative for the mutagenicity for both the -S9 and +S9 tests, which assess the mutagenicity of the sample itself and its metabolites, respectively.