Search

Background Yacon roots contain remarkable amounts of prebiotic fructans and rare antioxidant phenolics. Plant-based foods present a short shelf-life. In the case of yacon, fresh storage causes rapid depolymerization of fructans. Therefore, many attempts to extend yacon roots shelf-life have been made over the last years. Scope and approach This review aims at presenting the effect of processing methods on yacon roots health-promoting compounds, such as fructooligosaccharides, inulin and phenolics. Additionally, yacon-based products health-promoting properties, such as antioxidant enzymes activity, lipid peroxidation inhibition and other metabolic parameters that reflect intestinal health, are presented. An overview of the impact of processing on health-promoting compounds retention/concentration is shown. Yacon-based products with higher values of health-promoting properties are pointed out. Key findings and conclusions Innovations have been incorporated in the main methods used for processing yacon along the years, namely drying and blanching, such as the use of vacuum, foam-mat drying, use of salts and acids in the blanching solution, and combination between blanching and drying. Results show that fructan retention was superior when using hot air drying preceded by blanching with salts and acids. Phenolic content in solids was higher when using spray drying. Phenolic content in liquids was higher when using blanching combined with lactobionic acid addition to the juice. In addition, yacon-based products, especially flours, promote intestinal health by means of affecting metabolic parameters like microbial counts, short-chain fatty acids content, antioxidant enzymes expression and postprandial glycemic response.

Plant-based foods are recognized by their remarkable content of bioactive compounds. In an attempt to increase plant-based foods shelf-life, technologies like drying can be used. Foam-mat drying is a mild drying technology that removes water, usually by using hot air, from a foam obtained by the whipping of a liquid or semi-liquid food added with a foaming agent. There are several reports on the use of foam-mat drying for extending plant-based foods shelf-life, including reports on the effect of drying on their bioactive compounds. Therefore, this study aimed at reviewing the literature on the impact of foam-mat drying on plant-based foods bioactive compounds published in the last 10 years. Results show that short foam-mat drying time is beneficial to bioactive compounds retention. In addition, hot air temperature between 40-65 °C, foam thickness between 0.2 and 1 cm and the use of egg white as one of the foaming agents leads to high bioactive retention. Egg white is also the most used foaming agent. Regarding the mathematical models used for fitting the foam-mat drying kinetics, the Page model was shown as the most proper model. Foaming agent concentration is a delicate parameter, as its increase in foam formulation may beneficially enhance drying rates but, at the same time, it dilutes bioactive compounds and may cause their loss by oxidation. In conclusion, foam-mat drying stands out as a suitable technology for producing food powders with high bioactive retention.

In an attempt to obtain shelf-stable litchi fruit with preserved nutritional quality and good sensory features, quarters of peeled and pitted fruits were vacuum dried at 50, 60 and 70 °C at a constant pressure of 8.0 kPa. The product was assessed for its vitamin C, total phenolics and texture (hardness). In addition, the product with the best texture was assessed for its shelf-life by means of accelerated testing. Results suggest that vacuum dried litchi retained almost 70% of the vitamin C and total phenolics when compared to frozen fruits (control). Vitamin C and phenolic compounds content significantly decreased with drying, while no difference was found between different drying temperatures. Hardness increased with drying temperature. The sample dried at 70 °C presented crispness, which is a desired quality feature in dried fruit products. This sample was subjected to shelf-life evaluation, whose result suggests a shelf-life of eight months at 23 °C. Total color change (CIE ΔE00) was the expiry criterion. Vacuum drying was a suitable technique for producing shelf-stable litchi fruit with good texture while preserving its desirable original nutrients. Consumption of vacuum dried litchi may be beneficial to health due to its remarkable content of phenolic compounds and vitamin C.

Jams are popular products around the world, being made basically from one or more fruits, pectin, an edible acid (usually citric acid), and sugar. They are an interesting option for expanding the limited market share of exotic fruits, especially because they need no refrigeration and, in this way, they can reach all possible markets. Their extended shelf-life is assured by means of an evaporation concentration process in which temperatures above 100 °C followed by hot filling take place combined with an acidic pH and a high-soluble solid content. Another convenient way to consume exotic fruits in by means of pulps, which can be used in the preparation of juices, desserts, ice creams, and so on. In this sense, studies have been conducted to evaluate the suitability of the different exotic fruits available for producing jams and pulps and to characterize the physical, chemical, and sensory quality of the yielded products. This chapter is devoted to these studies.

Besides beverages, jams, and pulps, the literature on exotic fruits brings reports on various other products, like structured fruits, dried fruits, ice creams added with fruits, minimally processed fruits, marmalades, etc. These studies are brought to the reader in this chapter. Structured fruit and dried fruit received special sections because they are subjects in which there are several works published. The former is a relatively new kind of product that uses hydrocolloids to form a sort of natural food gel of extended shelf-life and pleasant sensory quality. The latter is possibly the most ancient processed food and will always be a good option as it does not require many costs with storage and transportation and presents a very long shelf-life. Additionally, this chapter brings the effect of the processing techniques on exotic fruits chemical and nutritional quality and, in some cases, the processing conditions used for assuring the product shelf-stability.

Fruit beverages are appreciated all around the world because they are a convenient way of consuming fruits, commonly referred to as health-promoting foods. In the case of exotic fruits, there is an extra advantage, that is the fact that it is commonly hard to find these fruits in the market due to their limited commercial production and market share. Processing into juice usually involves a pasteurization step which assures a shelf-life of months time enough for the juice to reach local, regional, and even international markets. This chapter brings to the reader studies involving exotic fruits from different continents, each one dealing with one or more exotic fruits, the analyses used for characterizing them, and the processing techniques used for extending their shelf-life.

Besides the well-known positive impact of blanching on color, the benefits of blanching can reach texture and even flavor. These effects are usually related to the activation or inactivation of key enzymes. Furthermore, reports on the positive effect of blanching on physicochemical parameters of foods are numerous. This chapter aims at reporting the effect of blanching on the physical, chemical, and sensory quality of foods. Given the importance of potatoes for mankind and the numerous studies on the blanching of potatoes, the first section of the chapter is devoted to this topic. Subsequently, blanching of miscellaneous foods is dealt with. The results of these studies are usually presented together with hypotheses that try to explain the observed behavior of foods as affected by blanching. Several equations used for modeling changes in color, texture, and enzymatic activity during blanching are presented. This chapter is very helpful for understanding the impact of blanching on food quality from a general perspective.

As stated in previous chapters, a conventional blanching treatment consists in immersing food pieces, usually vegetables, in hot water with the main goal of inactivating enzymes. Nevertheless, this treatment presents some drawbacks such as the high production of effluents and the leaching of nutrients. The use of steam for blanching foods might be considered as an innovation, since the aforementioned drawbacks are less pronounced than in hot water blanching. Nevertheless, the use of thermal treatments for fruits, for example, provides them with a cooked flavor and texture that is not appreciated by many consumers seeking for fresh-like fruit products. In this sense, this chapter brings studies on innovations on blanching techniques, from improvements on typical blanching processes to substitution of blanching by cutting edge techniques for enzymes inactivation. Technologies dealt with in the chapter include, for example: high-pressure processing, ultrasound, microwave blanching, Ohmic blanching, infrared blanching, and radiofrequency blanching. Novel blanching techniques will be presented separated by type and chronologically in order for the reader to understand the advances in the each technology over the years.

Drying is an ancient method designed to increase food shelf-life by means of water removal. The use of blanching prior to drying is a common practice, especially when low drying temperatures are used, because blanching inactivates enzymes responsible for undesirable sensory changes. However, a number of reports suggest that blanching is also able to improve the drying performance. In this chapter, such studies will be presented and discussed. Figures showing the positive impact of blanching on drying performance include data on drying kinetics, water activity kinetics, and effective moisture diffusivity, all of them showing that blanching is usually favorable for accelerating the subsequent drying process. Proposed mechanisms for this effect include cell membrane disruption, softening, removal of natural waxy layers, loss of turgor, and pores enlargement. Nevertheless, a couple of studies showing insignificant or negative effects of blanching on drying performance are also available. The impact of blanching on dried product quality is also dealt with in this chapter since product quality assessment is usually carried out in drying studies. Since not all foods behave the same way, the choice for blanching before drying must be made on the basis of experiments, thereby assuring that the impact of blanching will be favorable to the drying process and the product quality achieved will be desirable.

This work aimed at studying the drying kinetics of yacon slices during vacuum drying and evaluating the effect of drying temperature, slice thickness, and citric acid concentration in the enzymatic...

This study was aimed at studying the effect of the drying temperature, slice thickness and citric acid concentration in the enzymatic browning inhibition solution on yacon slices' color and texture during vacuum drying and at optimizing the operation conditions toward final product quality. Color was expressed as CIE L*a*b* and CIE L*C*h* parameters, and texture was expressed as hardness. Vacuum drying caused decrease in L* and reflectance and increase in a* and b* values. Product hardness varied little on initial stages of drying, followed by softening and hardening. The effects of the factors on final product L* value and average value of b* and C* were very well fitted by polynomial models. The desirable product quality is represented by high L* values (low browning), high b* values (golden yellow color) and high C* values (high colorfulness), which can be achieved by combining high-drying temperature, low slice thickness and high acid concentration. PRACTICAL APPLICATIONS This work provides optimized drying conditions in order to obtain shelf-stable dried yacon with ideal appearance. Yacon is a functional tuber that is rich in phenolic compounds and dietary fiber. Appearance is the first quality attribute evaluated by consumers when choosing a food product. Vacuum drying showed to be appropriate for drying yacon, as lower temperatures can be used in this process. In this way, the functional and sensory features of yacon are preserved. This work can be used as a reference for drying yacon, increasing the shelf life of this food system while preserving its desirable original features.

In this study, the apparent viscosity of a skim milk based dessert was optimized through the use of a 5-level Central Composite Design. The effect of carrageenan, guar gum, sucrose and pH on the dessert's apparent viscosity was esti-mated. The dessert's flow behavior was also analyzed. A rotational viscometer was used for the the apparent viscosity measurements. All formulations presented a non-Newtonian, shear-thinning behavior. Except for carrageenan concentration, all of the design factors affected apparent viscosity, being the effects better described by second order polynomial models. The following combinations of the variable ingredients yielded the best apparent viscosity: guar gum concentration: 0.0-0.315% (w/w) and sucrose concentration: 5.000-8.615% (w/w); or guar gum concentration: 0.109-0.315% (w/w) and sucrose concentration: 5.000-11.000% (w/w); in both cases, carrageenan and pH were kept at 0.020% (w/w) and 6.50, respectively.

Over the last decades, lettuce has been associated to several foodborne outbreaks. The present study surveyed the microbiological and parasitological contamination of green leaf lettuce used in sandwiches sold in snack bars in Curitiba, Paraná, Brazil. Lettuce was collected before and after commercial washing. Such procedure was made by holding and rotating the whole lettuce or separated leaves under the faucet of a sink with cold water for 10-30s. Three samples of 25g of lettuce leaves from each snack bar were assessed for mesophilic aerobic bacteria, molds and yeasts, Escherichia coli, incidence (%) of general parasites, Salmonella spp, Staphylococcus aureus. The obtained mean counts, expressed as Colony Forming Units per gram of lettuce, were respectively: 5.9 x 106; 6.4 x 103; 2.1 x 102; 73%, for non-washed samples; and 7.3 x 104; 5.9 x 103; 1.0 x 102; 18%, for washed samples. The water washing, as it has been performed in the food establishments investigated, showed to be inefï¬ cient for sanitizing lettuce. Though Salmonella and Staphylococcus aureus were not found, the results refl ect unsanitary production practices and show that the assessed lettuce has been a source of biological hazard.

The objective of this research was to study the influence of different blanching conditions on potato stick color, oil uptake and water activity (Aw ), and optimize the process by means of the desirability function. Color was expressed as properties of L*a*b*and L*C*h*spaces, some of which were fitted by Box–Behnken quadratic models. The blanching optimum conditions were as follows: a concentration of ascorbic acid of 0.2 g/100 g potato, a time of 5.5 min and a temperature of 69C. Responses obtained when using these conditions were −1.68 a*value and −86.31° h*value, which represent a hue in potatoes unaffected by the enzymatic browning. Regarding oil uptake, some of the blanched sticks absorbed 31% less oil than the control. Regarding Aw, all blanched samples presented lower values than the control, suggesting that blanching increases the shelf life of fried potatoes. PRACTICAL APPLICATIONS This article presents that the optimized blanching process conditions were able to control the enzymatic browning in potato sticks prior to frying, and thus improved their quality. Furthermore, some blanching conditions were found to decrease by 31% the oil uptake in potato sticks, leading to healthier fried potatoes. Finally, blanching significantly decreased the Aw in all fried potato sticks evaluated, suggesting that this process is also a way to increase the shelf life of fried potatoes.

Microwave-vacuum drying is one of the most promising techniques for drying foods with proper quality at a relatively low cost. The short drying times make this process cost-effective thus allowing large scale dried food production. As shown in this chapter, microwave-vacuum dried foods include bananas, grapes, pomegranates, carrots, seeds, gels, honey and snacks. A couple of equations for calculating drying efficiency and modelling drying kinetics are presented. The values of effective moisture diffusivity for some other products are also presented. Most of the studies reported here investigate the effect of process conditions, especially vacuum pressure and microwave power level, on quality and engineering aspects of selected products. Some of them dealt with process optimization. The chapter presents studies from end the past century, when microwave-vacuum drying of foods started to be studied, until nowadays. The evolution of this technique can be confirmed by technical advances introduced over the years such as the use of product rotation, power intermittency, control of product temperature, osmotic pretreatment and improvements on the equipment design.

This chapter deals with general aspects of food vacuum drying. Food drying under vacuum presents several advantages over conventional atmospheric drying. Vacuum drying takes place in the absence of oxygen and at mild temperature, thus preserving most of the food nutritive and sensory characteristics. Nevertheless, it is usually a more costly process when compared to atmospheric drying. Conventional vacuum drying, freeze-drying, microwave-vacuum drying and related processes are the most known vacuum drying processes. While conventional vacuum drying is the cheapest process, microwave-vacuum drying is the fastest and freeze-drying provides the product with the best quality. On the other hand, conventional vacuum drying yields products of inferior quality and freeze-drying is very expensive, while microwave-vacuum drying presents intermediate costs and provides the product with acceptable quality. Summarizing, each one of these processes presents strengths and weaknesses in terms of engineering and quality aspects. The choice for one or other vacuum drying technique will depend on the needs to be fulfilled.

This chapter deals with the simplest way to perform the vacuum drying of foods. Such process is usually performed as a batch in a vacuum oven. The chapter presents studies carried out from year 2001 to year 2014 as surveyed in electronic databases. The vacuum dried foods used as material in these studies include herbs, fruits, vegetables and mushrooms. Most of these foods present health-promoting (functional) properties which are preserved even after drying due to the special conditions (low heating and low oxygen content) used during vacuum drying. Effective moisture diffusivity, a property related to the ability of moisture to migrate from the product to the environment, was calculated in many of these studies and the respective values are presented here. An equation for calculating this parameter in foods is also presented. Several thin-layer drying models, which are equations that fit the values of moisture content during drying, are also presented.

This study aimed at investigating the effect of vacuum drying temperature on drying kinetics, drying rates, effective moisture diffusivity and quality parameters of litchi fruits. Peeled litchi quarters were dried at 50–70 °C at an absolute pressure of 8 kPa. Results show that the vacuum drying occurred in the falling rate period. Drying rates increased with drying temperature. The Page model provided the best fit to the drying kinetics. Effective moisture diffusivity ranged between 1.997 × 10−9 and 5.012 × 10−9 m2/s. The temperature dependence of the effective moisture diffusivity was well described by an Arrhenius-type equation. The activation energy for moisture diffusion was 41.81 kJ/mol. Drying temperature did not significantly affect product sensory acceptance, density, shrinkage and rehydration. The products dried at 50 and 70 °C presented slightly superior texture and flavor, while the product dried at 60 °C presented significantly higher lightness and lower water activity. Practical Applications This work provides valuable information on the vacuum drying of litchi fruits, which are appreciated in many countries due to their pleasant sensory characteristics. Vacuum drying is not a costly drying method. At the same time, vacuum drying produces dried foods of relatively good quality. This study could be used as a reference by small and medium scale food processors interested in producing dried litchi of good quality with relatively low investment in equipment. The understanding of the influence of drying temperature on quality parameters is useful for deciding which temperature is more appropriate depending on the desired quality aspects, while the calculation of engineering parameters is important for designing the drying process.