Authors:S. Dragoev, D. Balev, G. Ivanov, B. Nikolova-Damyanova, T. Grozdeva, E. Filizov, and K. Vassilev
Lipid oxidation is one of the main factors responsible for the quality loss in refrigerated and frozen stored fish products. The aim of the study was to evaluate the effect of superficial treatment of Atlantic salmon (Salmo salar) with dihydroquercetin (DHQ) solutions on the hydrolytic and oxidative changes in fish lipids during refrigerated storage. It was found that treatment with DHQ solution (1.0 g l−1) reduced approximately twice the free fatty acids content of chilled stored salmon. After 11 days of storage at 1 °С, the contents of hydroperoxides (HPO) and 2-thiobarbituric acid reactive substances (TBARS) of these samples decreased with 45.00 and 0.91 mg MDA/kg, respectively. The share of saturated fatty acids (SFA), monounsaturated fatty acids (MUFA), and polyunsaturated fatty acids (PUFA) in control and experimental samples did not differ significantly (P>0.05). Results obtained show that the superficial treatment of salmon with DHQ solution (1.0 g l−1) delayed the hydrolytic and oxidative changes in fish lipids significantly, thus preserving the salmon freshness up to 11 days of storage at 1 °С.
The effect of organic acids on the melanosis inhibition and shelf-life on shrimp was investigated. Shrimps were treated with 1% solutions of lactic, citric, acetic acids, sodium metabisulfite (0.3%) and their various combinations. After treatments the shrimps were stored at 4 °C and evaluated for melanosis every day and quality changes on every other day. Combinations with sodium metabisulphite were the most effective in delaying melanosis. Citric and lactic acids extended shelf life to a lesser extent but acetic acid had no effect.
Authors:S.A. Aouanouk, A. Mouheb, R. Absi, and R. Zazoun
A major problem related to heat treatment of milk is formation of deposits. This is due to the chemical alteration of β-lactoglobulin protein that leads to formation of coatings on the walls of the equipment. These deposits induce losses in the thermal performance of the heat exchanger. In order to provide an adequate prediction of these deposits, we present a two-dimensional (2D) modelling study of the channel of a plate heat exchanger. Compared with the former studies, where the domain is related to a single plate, our work is related to the area between the two plates. This approach will allow a better understanding and description of the evolution and behaviour of β-lactoglobulin protein. Equations for fluid flow, energy, and fouling were resolved. Special boundary conditions had been implemented to link the amount of deposits with thermal transfer. Predicted results for the amount of fouling deposit on the wall were validated by comparisons with experimental data available in literature. The behaviour of β-lactoglobulin protein was studied by analyzing its distribution in the channel.
Authors:Y. Cao, Y. Wang, K. Ji, S. Dai, Q. Li, C. Duan, P. Chen, Y. Wu, Y. Sun, H. Luo, Y. Wang, and P. Leng
Influence of different maturity stages and treatments of ethephon, exogenous ABA, and fluridone on the ripening and hormone level of ‘Zhonghuashoutao’ peach during development and post-harvest storage were investigated. The accumulation of endogenous ABA appeared at the onset of ripening and peaked at two weeks before harvest. Fruit firmness decreased, while ethylene release and SSC/TA increased sharply after a maximum peak of ABA, which have triggered the initiation of the fruit ripening. The fruits, harvested at 170 d when fruits have ripened and stored at 20 °C, showed an ethylene climacteric peak, and the pulp started softening normally, and the SSC/TA value increased. Compared with them, the immature green fruits harvested at other dates, could not mature normally due to the lack of normal reciprocity between ABA and ethylene. The ethylene release was promoted by the treatment of exogenous ABA and ethephon during ripening until the endogenous ABA reached a maximum value. However, fluridone treatment showed an inhibitory effect. The above-mentioned changes occurred again in the peach fruits after harvest. The results indicated that both ABA and ethylene play important roles in peach ripening, and their action depended on the ripening stage of peach.
Authors:L. Silva, G. Maia, P. Sousa, R. Figueiredo, M. Afonso, M. Gonzaga, C. Gomes, and E. Figueiredo
The purpose of this experiment was to evaluate the effect of heat treatment on the rheological properties of mixed nectars, based on cashew apple, mango, and acerola pulps. Ten different formulations with different mass fractions of cashew apple, mango, and acerola pulps were prepared using a simplex centroid design [with a total of 35% (w/w) pulp] and submitted to heat treatment at 90 °C for 1 min. Samples were collected before and after heat treatment and characterization of their rheological properties was carried out. The rheological behaviour was obtained at 25 °C, with shear rate ranging from 108 to 500 s−1 (upward curve) and from 500 to 108 s−1 (downward curve) for 1 min with 25 readings for each curve. The Ostwald de Waele model showed to be a good fit for all formulations studied, which showed a non-Newtonian behaviour and a pseudoplastic character. Results of apparent viscosity for the non-heated formulations were well fitted by the linear model and the heat treated formulations by the cubic model. The heat treated formulations had higher (P<0.05) values of consistency index and apparent viscosity, as well as lower (P<0.05) values of flow behaviour index compared to non-heated formulations. The rheological characterization of these formulations is a very useful tool during product development and processing control of mixed nectars of fruit juice.
Clostridium perfringens is a widely distributed foodborne pathogen. Its ability to survive cold encounters could contribute to its persistence in foods and the potential to cause disease. In this work five cold-shock proteins (101, 82, 70, 45 and 10 kDa) were induced by cold-shocking C. perfringens FD-1041 from 43 °C to 28 °C, as revealed by labeling with L-[35S]methionine and cysteine followed by gel electrophoresis. Cold shock also increased the cold tolerance of the cells at least fifteen fold. The acquired tolerance was maintained for 2 h after the cold treatment. This ability of C. perfringens could improve the survival in foods and present a significant hazard.