Band 13, Heft 8 -

This study evaluates the effect of low temperature (60, 64 and 68 °C) and different times (15 and 20 min) of cooking on physicochemical and sensory characteristics of confit cod and analyzes confit cod in a non-destructive way by means of magnetic resonance imaging (MRI) and computer vision techniques. Higher scores for acceptability and flavor in 60 °C–20 min and 64 °C–20 min samples and some physicochemical differences were found. These results allow distinguishing four groups of confit cods as a function of cooking conditions – 60 °C–15 min/68 °C–15 min/68 °C–20 min/60 °C–20 min, 64 °C–15 min, 64 °C–20 min – and proposing to cook confit cod at 60–64 °C during 20 min. Prediction by means of computational texture features from MRI gave moderate-to-good correlation (0.6–0.75) for six quality attributes and very good-to-excellent relationship (0.75–1) for other six. Thus, computational texture features seem to be appropriate to determine the quality attributes of confit cod in a non-destructive way.

Almonds can be classified based on their shell characteristics from soft to hard shell varieties. The majority of Australian and Californian varieties have soft shell properties. Most Spanish almond varieties have hard shells. Although having a hard sealed shell protects the kernel from insect damage it affects their processability. Common commercial almond processing equipment simultaneously compresses and shears the almonds and this creates a high percentage of damaged kernels from the broken shell being forced into the kernel, particularly for hard shell varieties. This paper shows that for the soft shell variety ‘Nonpareil’ and the three hard shell varieties of ‘Marcona’, ‘Tarraco’ and ‘Vyro’ that conditioning by soaking in water and resting before processing improves the recovery of undamaged kernel when shelling using impact. The impacts were applied by feeding the almonds into a rotating impellor and throwing them onto a stationary outer wall. An effective conditioning process resulted in the kernel moisture content increasing from 6% to 14% for hard shell and to 11% for ‘Nonpareil’ varieties. The conditioning process was measured to reduce the amount of scratched, chipped and broken kernel, and hence increased the recovery of undamaged kernel. After shelling, the conditioned kernel needed to be dried back to a 6% moisture content to be suitable for storage. Hence, the industry would be able to increase its recovery of undamaged kernel by changing to an impact shelling process using suitably conditioned almonds.

The quality of starch gel could be enhanced by sugar and hydrocolloid. Sucrose (0, 10 % and 20 %) and xanthan gum (Xan) (0.3125 %) were added in the tapioca starch (TS) gels (25 %w/w TS and TS/Xan gels) for quality investigation. Sucrose increased gelatinization temperatures of starch mixtures. Moisture content and water activity decreased with increasing sucrose content and Xan addition. Freeze–thaw stability of TS and TS/Xan gels with and without sucrose was evaluated. Sucrose and Xan decreased water separation from repeated freeze–thaw cycles. A regression model for predicting water separation from Xan, sucrose and selected freeze–thaw cycle was developed and showed a good predictability. After keeping the TS and TS/Xan gels at 5 °C for 7 and 14 days, the hardness of TS and TS/Xan gels increased with increasing sucrose content but was retarded by adding Xan ( p <0.05), suggesting Xan impeded the structure formation contributed from amylose molecule association during cold storage.

Open pore porosity of spaghetti was measured by helium (He) gas pycnometer and mercury (Hg) porosimetry and it was observed as 0.025 and 0.023, respectively. Pore size distribution curve from mercury porosimetry indicated two sharp crests, at alternate position of 59±8 μm and 6.4±0.9 μm diameter pore; while Scanning Electron Microscopy (SEM) showed two types of pores, first class was cracks and second one was holes. The average width of the cracks (channel) and diameters of holes were determined as 3.6±1.5 µm and 1.0±0.3, respectively. The moisture sorption isotherm of spaghetti was measured by dynamic sorption method and modeled by Brunauer-Emmett-Teller (BET) and Guggenheim-Anderson-de Boer (GAM) models. The values of BET monomolecular layer were observed as 3.24 and 5.91 kg water/kg dry solids, respectively for adsorption and desorption cycles.

The impact of gellan (GL) at different levels (5–20 % of total solid) on the properties of fish gelatin (FG) gels was studied. Gel strength and hardness of FG/GL mixed gel increased, while springiness and cohesiveness decreased as the levels of GL were increased ( p < 0.05). Gelling and melting temperatures also increased with increasing levels of GL incorporated ( p < 0.05). L* - and b* -values of FG/GL mixed gel decreased, whereas ∆E* -value increased with increasing GL levels ( p < 0.05). Microstructure studies revealed that denser structure with very small voids in gel network was observed upon GL addition. The addition of GL at a low level (5 %) had no adverse effect on sensory property, and no effect on syneresis of FG/GL mixed gels. Therefore, the addition of 5 % GL can be used to improve gelling property of FG via increasing gelling points without affecting sensory property of the resulting gel.

In this paper, short- and medium-wave infrared radiation (SMIR) drying characteristics of kiwifruit slices with/without osmotic dehydration (OD) were investigated. High fructose corn syrup (HFCS) was selected as the best osmotic solution and coupled with SMIR. Both infrared drying processes with/without OD occurred mainly in the falling rate period. Results indicated that the Logarithmic model and Page model were best in predicting moisture transfer for the kiwifruit slices with and without OD, respectively. The values of effective diffusivity ranged from 4.10×10 ‒10 m 2 /s to 9.52×10 ‒9 m 2 /s and from 3.10×10 ‒10 m 2 /s to 1.16×10 ‒8 m 2 /s for kiwifruit slices with and without OD, respectively. During the overall falling rate period, the activation energy value was 29.51 kJ/mol and 27.44 kJ/mol for the osmosed and non-osmosed kiwifruit slices, respectively. As compared with non-OD, OD pre-treatment could improve the drying characteristics, decrease color change and increase the retention ratios of ascorbic acid and chlorophyll.

The powder mixture of gum arabic and maltodextrin was produced by spray drying. The inlet air temperature of spray dryer was varied from 160 °C to 260 °C and the maltodextrin content was varied from 0 to 50 % in the feed solution with the concentration of 42.5 % (w/v) total solids by weight. The properties of the finished product were characterized to examine the impact of changes in these operating parameters. The results showed that: the inlet air temperature had a stronger influence on the properties of finished product than the MD/GA ratio, whereas the feed rate was more clearly affected by the MD/GA ratio. Two optimal parameters obtained include MD/GA ratio equal to 0.615 and the inlet air temperature of spray dryer Te = 258 °C.

The potential of reduced-pressure radio-frequency air plasma (RFAP) in the modification of konjac glucomannan (KGM) was investigated. KGM film was exposed to 100 W RFAP for 50 s, 100 s, 150 s, 200 s, and 250 s, ground, and then subjected to various characterizations. Fourier Transform Infrared Spectroscopy (FTIR) revealed that RFAP treatment increased the content of –OH groups in KGM, with the lowest and highest rise occurring at the exposure durations 150 s and 250 s, respectively. RFAP radiation decreased the solubility of KGM at certain exposure durations, but slightly increased its thermal stability. Exposure to RFAP for 150 s and 250 s increased the hardness of the resultant KGM gel, but decreased the viscosity and elasticity of the KGM solution in a duration-dependent manner. Scanning Electron Microscope (SEM) observation revealed that RFAP treatment led to rougher surfaces and XRD (X-Ray Diffraction) analysis indicated the destroyed crystallinity of KGM. Hence, RFAP has potential application in the modification of KGM.

Xylitol is fast gaining ground over other sugar substitute owing to its high sweeting and low calorie properties. Menthol, a flavor agent, is widely used in food production. However, menthol can easily sublimate, while xylitol has a strong hygroscopicity. In this study, the co-crystals of xylitol with menthol are performed aiming to improve their negative properties. The results indicated that the water activity of co-crystals varies from 0.126 to 0.370. Meanwhile, the hygroscopicity of co-crystals is reduced to some extent compared with xylitol. Differential scanning calorimetry results demonstrated that co-crystals have similar thermal properties. What’s more, co-crystals have nearly identical X-ray diffraction patterns with xylitol. Thus, it is suggested that the microstructure of co-crystals is influenced mostly by the compound with a high ratio. Overall, this study can convey important idea for the development of food new materials, also the control and application based on co-crystallization techniques in food industry.

Fluidized-bed granulation has received considerable attention within the food process industry because granulated products often have improved flowability and appearance, and sometimes have specifically enhanced physical properties. In this study, the rheological properties of granulated xanthan gum (XG), commonly used as a main ingredient in food thickeners for dysphagia diets, were investigated at different concentrations (0, 5, 10, and 15 % w/w) of maltodextrin (MD) as a binder at different concentrations. Flowability and cohesiveness of granulated XG powder was also evaluated in terms of as Carr index (CI) and Hausner ratio (HR) were also investigated. The consistency index, apparent viscosity, storage modulus (G’) and loss modulus (G”) of granulated XG were significantly higher than those of non-granulated XG and granulated XG without binder (0 % MD). The tan δ values of granulated samples were lower compared with that of a non-granulated sample, indicating that their elastic properties were more pronounced because of the granulation. These rheological results also showed that there were no noticeable changes in flow properties between 0 % and 5 % MD concentrations, whereas the G’ and G” values at 10 % MD were much higher than those at other concentrations. The granulation process by MD binder also enhanced considerably flow characteristics of XG powder.