Effect of sugar composition on the water sorption and softening properties of cookie

Thermomechanical transitions of meat-analog based fried foods batter coating

This study aimed to characterize the thermomechanical transitions of meat-analog (MA) based coated fried foods. Wheat and rice flour-based batters were used to coat the MA and fried at 180 °C in canola oil for 2, 4 and 6 min. Glass-transition-temperature (Tg) of the coatings were assessed by differential scanning calorimetry, directly after frying or after post-fry holding. Mechanical texture analyzer and X-ray microtomography were employed to assess textural attributes and internal microstructure, respectively. Batter-formulation substantially impacted the Tg of fried foods coating i.e., crust. Tg of fried foods crust were ranged between -20 °C to -24 °C. Tg was positively correlated with frying time and internal microporosity (%), whereas negatively correlated with moisture content. Internal microstructure greatly influenced the textural attributes (hardness, brittleness, crispiness). Post-fry textural stability considerably impacted by Tg. Negative Tg value explains post-fry textural changes (hard-to-soft, brittle-to-ductile, crispy-to-soggy) of MA-based coated products at room-temperature (25 °C) and under IR-heating (65 °C).

Tailoring microstructure and mechanical properties of pectin cryogels by modulate intensity of ionic interconnection

Porous morphology and mechanical properties determine the applications of cryogels. To understand the influence of the ionic network on the microstructure and mechanical properties of pectin cryogels, we prepared low-methoxyl pectin (LMP) cryogels with different Ca2+ concentrations (measured as R-value, ranging from 0 to 2) through freeze-drying (FD). Results showed that the R-values appeared to be crucial parameters that impact the pore morphology and mechanical characteristics of cryogels. It is achieved by altering the network stability and water state properties of the cryogel precursor. Cryogel precursors with a saturated R-value (R = 1) produced a low pore diameter (0.12 mm) microstructure, obtaining the highest crispness (15.00 ± 1.85) and hardness (maximum positive force and area measuring 2.36 ± 0.31 N and 12.30 ± 1.57 N·s respectively). Hardness showed a negative correlation with Ca2+ concentration when R ≤ 1 (-0.89), and a similar correlation with the porosity of the gel network when R ≥ 1 (-0.80). Given the impacts of crosslinking on the pore structure, it is confirmed that the pore diameter can be designed between 56.24 and 153.58 μm by controlling R-value in the range of 0-2.

Why Does Cronobacter sakazakii Survive for a Long Time in Dry Environments? Contribution of the Glass Transition of Dried Bacterial Cells

To investigate the mechanism of adaptation of Cronobacter sakazakii to desiccation stress, the present study focused on the glass transition phenomenon of dried bacterial cells, using a thermomechanical technique. The mechanical glass transition temperature (T_g) of dried C. sakazakii cells per se, prepared by different drying methods (air drying and freeze-drying) and with different water activity (a_w) levels (0.43, 0.57, 0.75, and 0.87), were determined. In addition, we investigated the survival of two strains of C. sakazakii (JCM 1233 and JCM 2127) prepared by different drying methods under different storage temperatures (4, 25, and 42°C) and a_w conditions (0.43 and 0.87). While the T_g of the air-dried C. sakazakii cells increased as the a_w decreased, the freeze-dried C. sakazakii cells showed an unclear a_w dependency of the T_g. Air-dried C. sakazakii cells showed a higher T_g than freeze-dried C. sakazakii cells at an a_w of <0.57. Freeze-dried C. sakazakii cells were more rapidly inactivated than air-dried cells regardless of the difference in a_w and temperature. The difference between the T_g and storage temperature was used as an index that took into consideration the differences in the drying methods and a_w levels. As the difference between the T_g and storage temperature increased to >20°C, the dried C. sakazakii cells survived stably regardless of the drying method. In contrast, when the difference between the T_g and storage temperature was reduced to <10°C, the viable cell numbers in dried C. sakazakii cells were quickly decreased. Thus, the T_g is a key factor affecting the desiccation tolerance of C. sakazakii.

IMPORTANCE The mechanical glass transition temperature (T_g) of dried Cronobacter sakazakii cells varied depending on differences in drying methods and water activity (a_w) levels. Because the T_g of the dried bacterial cells varied depending on the drying method and a_w, the T_g will play an important role as an operational factor in the optimization of dry food processing for controlling microbial contamination in the future. Furthermore, the differences between the T_g and storage temperature were introduced as an integrated index for survival of bacterial cells under a desiccation environment that took into consideration the differences in the drying methods and a_w levels. As the difference between the T_g and storage temperature decreased to <10°C, the dried C. sakazakii cells were inactivated quickly, regardless of the drying methods. The relationship between T_g and storage temperature will contribute to understanding the desiccation tolerance of bacterial cells.

A review combining emerging techniques with classical ones for the determination of biscuit quality: advantages and drawbacks

The production of biscuit and biscuit-like products has faced many challenges due to changes in consumer behavior and eating habits. Today's consumer is looking for safe products not only with fresh-like and pleasant taste, but also with long shelf life and health benefits. Therefore, the potentiality of the use of healthier fat and the incorporation of natural antioxidant in the formulation of biscuit has interested, recently, the attention of researchers. The determination of the biscuit quality could be performed by several techniques (e.g., physical, chemical, sensory, calorimetry and chromatography). These classical analyses are unfortunately destructive, expensive, polluting and above all very heavy, to implement when many samples must be prepared to be analyzed. Therefore, there is a need to find fast analytical techniques for the determination of the quality of cereal products like biscuits. Emerging techniques such as near infrared (NIR), mid infrared (MIR) and front face fluorescence spectroscopy (FFFS), coupled with chemometric tools have many potential advantages and are introduced, recently, as promising techniques for the assessment of the biscuit quality.

Glass transition and crystallization of solid model system of jujube slice as influenced by sugars and organic acids

To understand the specific contributions of amorphous sugars and organic acids to the quality of food matrix, the solid model system of jujube slice skeleton (JSS) was firstly established. Effects of fructose (F), glucose (G), malic acid (M) and citric acid (C) on the glass transition temperature (T_g) and crystallization of JSS were studied. JSS-F/G/M/C blends were prepared by osmosis in the solution at a range of 0 ~ 32 g/100 g. Sugars reduced the T_g in the system, structure of JSS-G/M blends was changed from "amorphous glassy" to "amorphous rubbery" by increasing the osmotic solute concentration. T_g was decreased from 50.8 to 14.0 °C when JSS was osmosed in a 4 g/100 g fructose solution. Organic acids induced their crystallization in JSS. The crystallinity of JSS-M immersed in 32 g/100 g osmotic solution concentration was increased from 2% to 75%. Fructose presented greater influence on the adverse quality of jujube slices.

Physical and structural characteristics of starch-based and conventional cookies: Water sorption, mechanical glass transition, and texture properties of their crust and crumb

The physical properties of starch-based cookie (gluten free and low fat) were compared with those of conventional cookie in consideration for the difference between crust and crumb parts. The internal porosity of the samples was measured by X-ray computed tomography. The starch-based cookie had a higher porosity (0.61) than the conventional cookie (0.42). The mechanical glass-transition temperature (T_g ) of the samples was evaluated by the thermal rheological analysis. The anhydrous mechanical T_g of the starch-based cookie was much lower than that of the conventional cookie. The T_g -depression of the starch-based cookie induced by water sorption was more gradual than that of the conventional cookie. For both types of cookie, the crust components were more resistant to water plasticizing than crumb components because of the difference of the equilibrium water contents at each water activity. For the texture analysis of crust components, the whole samples were fractured. The starch-based cookie had a lower fracture force, distance, and energy than the conventional cookie at each water activity point. For the texture analysis of crumb components, a portion of the crust was removed from the whole samples, and the exposed crumb was compressed by a plunger. From the texture profile, a normalized linear length was evaluated. The normalized linear length for the starch-based cookie was higher than that for the conventional cookie. These results were corresponded to the differences in the undeveloped gluten and fat contents.

Addition of Pachira aquatica oil and Platonia insignis almond in cookies: Physicochemical and sensorial aspects

This article investigated the use of Pachira aquatica (PA) fat and Platonia insignis (PI) nuts as ingredients in the preparation of cookies. Seven formulations containing PA fat and/or PI nuts were studied by changing the formulation proposed by AACC, and samples were evaluated considering physical-chemical, microbiological, and sensory characteristics. Formulations F1, F4, and F5 showed higher mass loss and lower expansion factor after cooking. Formulations F4, F6, and F7 presented a greater increase in diameter. In turn, formulations F5, F6, and F7 presented greater thickness. The content of fatty acids varied according to the composition of each biscuit, and formulations 2 and 3 presented the best lipid profile (oleic acid ~32%). In addition, it was observed that the addition of PI almond increased the fiber content (~7.15%). The sensory evaluation showed that formulation F5 obtained a score of 5, proving that the partial replacement of hydrogenated vegetable fat with PA fat and grated coconut with PI almond favored the panelists' purchasing decision. The results indicate that unconventional sources of lipids and nuts can be used without loss of quality in biscuits.

Relationship between glass transition temperature, and desiccation and heat tolerance in Salmonella enterica

Pathogenic bacteria such as Salmonella enterica exhibit high desiccation tolerance, enabling long-term survival in low water activity (aw) environments. Although there are many reports on the effects of low aw on bacterial survival, the mechanism by which bacteria acquire desiccation tolerance and resistance to heat inactivation in low-aw foods remains unclear. We focused on the glass transition phenomenon, as bacteria may acquire environmental tolerance by state change due to glass transition. In this study, we determined the glass transition temperature (Tg) in S. enterica serovars under different aw conditions using thermal rheological analysis (TRA). The softening behaviour associated with the state change of bacterial cells was confirmed by TRA, and Tg was determined from the softening behaviour. Tg increased as the aw decreased in all S. enterica serovars. For example, while the Tg of five S. enterica serovars was determined as 35.16°C to 57.46°C at 0.87 aw, the Tg of all the five serovars increased by 77.10°C to 83.30°C at 0.43 aw. Furthermore, to verify the thermal tolerance of bacterial cells, a thermal inactivation assay was conducted at 60°C for 10 min under each aw condition. A higher survival ratio was observed as aw decreased; this represented an increase in Tg for Salmonella strains. These results suggest that the glass transition phenomenon of bacterial cells would associate with environmental tolerance.

The use of of inulin, maltitol and lecithin as fat replacers and plasticizers in a model reduced-fat mozzarella cheese-like product

BACKGROUND

Mono-, di- and oligosaccharides, polyhydric alcohols and lipids are three main types of plasticizers used to process food materials. In the present study, inulin, maltitol and lecithin were selected as representative oligosaccharide, polyhydric alcohol and lipid fat replacers, respectively. Their effects on the physicochemical properties of reduced-fat mozzarella cheese were evaluated.

RESULTS

Lecithin reduced the hardness and increased the degree of free oil released. Inulin and lecithin decreased the hydrophobic interaction of reduced-fat cheese. Maltitol improved the elasticity of the reduced-fat cheese and increased the hydrophobic interaction within the casein matrix. Maltitol-added cheese had a lower glass transition temperature (T_g ) than the other cheeses. Maltitol significantly improved the stretchability of the reduced-fat cheese.

CONCLUSION

The results obtained in the present study suggest that maltitol is an effective fat replacer in reduced-fat mozzarella cheese and might enhance the cheese's functional properties. The T_g of cheese was related to the water and fat content, fat replacer addition and cross-linking degree of casein. The relationship between T_g and the physicochemical properties of cheese will be studied in further research. © 2019 Society of Chemical Industry.

Effect of Calcium Maltobionate on the Glass Transition Temperature of Model and Hand-made Hard Candies

Glass transition temperature (T _g) is an important parameter for the physical quality control of hard candies. In order to understand the applicability of calcium maltobionate to hard candy, effect of calcium maltobionate addition on the T _g of model and hand-made hard candies was investigated. Freeze-dried calcium maltobionate-sugar (sucrose containing a small amount of glucose-fructose mixture) and calcium maltobionate-reduced isomaltulose mixtures were prepared as model candies, and their anhydrous T _g was evaluated using a differential scanning calorimetry. The anhydrous T _g increased linearly with the molar fraction of calcium maltobionate. From these results, it was expected that calcium maltobionate can improve the physical stability of normal and sugarless candies. For comparison, various commercial candies were employed, and their T _g was evaluated using a thermal rheological analysis. The T _g values were in the range of 28-49 °C. The T _g values were higher than 25 °C, which is significant with respect to the physical stability of the candies. Calcium maltobionate-sugar and calcium maltobionate-reduced isomaltulose candies were prepared as hand-made candies. The calcium maltobionate-reduced isomaltulose candies had higher T _g than the calcium maltobionate-sugar candies at each calcium maltobionate content, although reduced isomaltulose has a lower T _g than sugar. At a high calcium maltobionate content, calcium maltobionate-reduced isomaltulose candy had an equivalent T _g to the commercial sugarless candies, and thus practically acceptable stability was expected. In the case of calcium maltobionate-sugar candies, there was a possibility that the hydrolysis of sugar reduced their T _g. Vacuum-concentration will be useful to improve the T _g of the candies.

Control of Physical Changes in Food Products

Food is a multicomponent system that mainly comprises protein, carbohydrate, fat, and water. During food processing and preservation, various physical changes (e.g., melting, crystallization, glass transition) occur in food products, affecting their quality. This chapter specifically examines the effect of physical changes on the quality of dry and frozen food products. Dry food products are commonly in an amorphous state. Therefore, glass transition occurs during their dehydration-rehydration processing. To control their texture and physical stability, it is important to elucidate the effects of water contents on the glass transition temperature of dry food products. Frozen foods consist of ice crystals and freeze-concentrated matrix. The formation of ice crystal and the dynamics of ice crystal evolution affect food quality. Therefore control of ice crystals is important for high-quality frozen food. Moreover, because freeze-concentrated matrix consists of solute that are plasticized by the unfrozen water and is in an amorphous state, it can undergo glass transition by freeze concentration. The physical state of freeze-concentrated matrix also strongly affects the stability of food quality during frozen storage.