Background Frozen dough technology could effectively extend the shelf life of bread to ensure the freshness, which is widely used and gradually replace the traditional bread production. However, during the production and storage of frozen dough, a series of problems could take place, such as inhibition of yeast activity, damage of the structure of the dough, leading to the deterioration of dough quality. Scope and approach This review summarizes the factors that affect the final quality of frozen dough, including yeast activity, dough structure and dough properties. Some effective methods for improving freeze tolerance of yeast, dough structure and dough properties are discussed, including addition of various additives, use of genetic engineering technique, optimization of freezing and storage conditions, and employment of novel freezing technology. Key findings and conclusions The addition of additives can not only improve the freeze tolerance of yeast but also maintain the rheological and thermophysical properties of dough. Through the modification of gene, freeze tolerance and fermentation ability of yeast can be improved. Optimizing freezing and storage conditions ensures the activity of yeast as well as dough network structure so that freezing damage due to ice crystals can be minimized. In addition, novel freezing technology such as ultrasound-assisted freezing can simultaneously accelerate the freezing process as well as generate fine and uniform ice crystals, thus protecting dough network structure.

Improving freeze tolerance of yeast and dough properties for enhancing frozen dough quality - A review of effective methods

Magister en Ciencia y Tecnologia de alimentos. Linea de Investigacion: Diseno y desarrollo de nuevos productos

Desarrollo y caracterización de recubrimientos activos a base de nanofibras electrohiladas de policaprolactona, quitosano y extractos oleosos de propóleos colombianos para la conservación de filetes de lomo de cerdo.

Application of ultrasound in combination with other technologies in food processing: A review.

High-pressure processing (HPP), microwaves (MW) and ultrasound (US) are used for pasteurization with minimum heat input. They also alter physico-chemical properties of milk proteins and enzymes. This article aims at identifying the important changes in milk proteins imparted by these three processing technologies. HPP dissociates casein micelles at low pH ( 400 MPa). MW treatment denatures whey proteins rapidly, even below their thermal denaturation temperatures. High-power MW treatment (e.g. 60 kW) deactivates enzymes by denaturing them. However, low-power controlled MW irradiation (e.g. 30 W) improves enzyme activity. Ultrasound can homogenize protein aggregates in dairy systems and cause whey protein denaturation. Sonication under applied pressure and heat (e.g. 3.5 kg/cm2, 126.5 °C) causes enzyme inhibition while mild sonication conditions can improve enzyme activity. Industrial relevance HPP, MW and US are gaining popularity in the dairy industry due to their ability to pasteurize and functionalize dairy streams with minimal heat input. This review offers insights into how these technologies can be used in isolation or in combination to alter milk proteins and enzyme activity for different academic and industrial applications. However, to fully understand the potential of HPP, MW and US treatment on dairy systems, further research is required in several areas including health related nutritional changes in milk and milk products caused by these technologies.

Effects of high pressure, microwave and ultrasound processing on proteins and enzyme activity in dairy systems — A review

In this study, a central composite design (CCD) was used for modeling and optimizing the operation parameters such as pH, initial tetracycline and persulfate concentration and reaction time on the tetracycline degradation using sono-activated persulfate process. The effect of temperature, degradation kinetics and mineralization, were also investigated. The results from CCD indicated that a quadratic model was appropriate to fit the experimental data (p < 0.0001) and maximum degradation of 95.01 % was predicted at pH = 10, persulfate concentration = 4 mM, initial tetracycline concentration = 30.05 mg/L, and reaction time = 119.99 min. Analysis of response surface plots revealed a significant positive effect of pH, persulfate concentration and reaction time, a negative effect of tetracycline concentration. The degradation process followed the pseudo-first-order kinetic. The activation energy value of 32.01 kJ/mol was obtained for US/S2O8
 2- process. Under the optimum condition, the removal efficiency of COD and TOC reached to 72.8 % and 59.7 %, respectively. The changes of UV–Vis spectra during the process was investigated. The possible degradation pathway of tetracycline based on loses of N-methyl, hydroxyl, and amino groups was proposed. This study indicated that sono-activated persulfate process was found to be a promising method for the degradation of tetracycline.

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Optimization of sonochemical degradation of tetracycline in aqueous solution using sono-activated persulfate process.

Osmotic dehydration (OD) is an operation used for the partial removal of water from plant tissues by immersion in a hypertonic solution, sugar and/or salt solution, to reduce the moisture content of foods before actual drying process. Research applications of osmotic dehydration to food processing in technology and in component transfer mechanisms are being carried out in several countries. This technique is a partial dehydration process to give the product a quality improvement over the conventional drying process. Osmotic dehydration is affected by several factors such as osmotic agent, solute concentration, temperature, time, size, and shape and tissue compactness of the material, agitation and solution/sample ratio. The osmotic dehydration step can be done before, during or after the conventional drying process to enhance the mass transfer rate or to shorten the duration of drying time the quality of osmotically dehydrated products is better and shrinkage is considerably lower as compared to products from conventional drying processes. This technique helps to conserve the overall energy relative to other drying procedures. In this review, the mechanism of osmotic dehydration is described. In addition, some factors that affect on mass transfer during osmotic dehydration reviewed. The major objective of this paper is to discuss the advantage of osmotic dehydration in terms of energy reduction.

Osmotic dehydration of fruits in food industrial: a review.

The concept of response surface methodology can be used to establish an approximate explicit functional relationship between input random variables and output response through regression analysis and probabilistic analysis can be performed. Response Surface Methodology (RSM) is a collection of mathematical and statistical techniques useful for the modeling and analysis of problems. By careful design of experiments, the objective is to optimize a response (output variable) which is influenced by several independent variables (input variables). An experiment is a series of tests, called runs, in which changes are made in the input variables in order to identify the reasons for changes in the output response. It is the process of identifying and fitting an approximate response surface model from input and output data obtained from experimental studies or from the numerical analysis where each run can be regarded as an experiment.

Application of response surface methodology: design of experiments and optimization: a mini review

Effect of chilling, freezing and thawing on meat quality: a review.

Advantages of freezing of dough are reduction of losses caused by aging of products. But freezing deteriorates the baking quality of frozen bread dough. These include gradual loss of the dough strength, reduced yeast activity and deterioration in the texture of the final product. The negative effects of freezing and defrosting of dough can be reduced by incorporating hydrocolloids in dough. Furthermore Biogenic ice nucleators, such as extracellular ice nucleators (ECINs) isolated from Erwinia herbicola, are a group of lipoglyco proteinsthat has been demonstrated to minimize the supercooling. Ice nucleation materials function as heterogeneous ice nucleators to minimize the supercooling of water. Mechanism of cryoprotective effects from extracellular ice nucleators was possibly that ECINs helped in preserving the viability of yeast cells during freeze/thaw cycles. At the end of this study we reviewed the ultrasound-assisted freezing; this method can improve the quality of frozen food without the need for additional additives. DOI: http://dx.doi.org/10.3126/ijls.v9i3.12439 International Journal of Life Sciences 9 (3): 2015; 1-7

Hydrocolloids and Cryoprotectant used in Frozen Dough and Effect of Freezing on Yeast Survival and Dough Structure: A Review

To achieve the balance between food quality and safety, there is a need to optimize conventional processing techniques currently applied in food industries and to develop novel processing techniques such as highpressure (HP) processing HP processing is a unique technology compared to other food processing technologies as pressure can result in enhancement or retardation of chemical and biochemical reactions as well as in both desired and undesired modification of biopolymers (eg enzyme (in)activation, gel formation)This paper focuses specifically on the effects of HP treatment on colour, flavour and texture of foods and tries to elucidate the mechanisms behind the observed changes in quality attributes

Mina Akbarian

Papers

Osmotic dehydration of fruits in food industrial: a review.

Application of response surface methodology: design of experiments and optimization: a mini review

Effect of chilling, freezing and thawing on meat quality: a review.

Hydrocolloids and Cryoprotectant used in Frozen Dough and Effect of Freezing on Yeast Survival and Dough Structure: A Review

Effect of high pressure processing of food characteristics: a review of quality aspect