Band 12, Heft 4 -

The objective of this study was to investigate the relationships of image texture properties with chewing behaviors, and mechanical properties during mastication of bread. Gray-level gradient co-occurrence matrix (GGCM) was used to process the images of boluses. The chewing behaviors were recorded by electromyography (EMG), and the mechanical properties were measured by texture analyzer. The results showed that among the texture features, the inverse difference moment (IDM GGCM ) was selected as the main parameter to describe the decomposition of boluses. IDM GGCM was positively related to the weight gain ( r  = 0.865, p  < 0.01), negatively correlated with hardness ( r  = –0.835, p  <0.01) and EMG activity per cycle ( r  = –0.767, p  < 0.01). GGCM is an effective texture analysis method that could correctly identify 70.1–80.8 % of food bolus images to the corresponding chewing cycles. This study provided a new clue for texture analysis of bread bolus images and offered data revealing the bolus property changes during the mastication of bread.

The aroma-active compounds of Jinhua ham were analyzed after isolation using simultaneous distillation extraction (SDE) and solid phase microextraction (SPME). In spite of the remarkable similarity between the dry-cured hams, the technological potential of combinations of both has never been explored before. Results show that 2, 6-dimethyl-pyrazine, hexanal, 2-heptanone, ethyl acetate and 2-pentyl-furan made the predominant contribution to the aroma of Jinhua ham. In fact, 28 volatile compounds were extracted using SDE, with cured, toasted, fatty and fried odors playing important roles in the “boiled ham”. At the same time, 29 volatile compounds with cured, sulfurous alliaceous and spicy herbaceous flavor were the main contributors to the ham odor. Furthermore, the contribution of each aroma-active component to the whole ham flavor profile was evaluated by aroma extract dilution analysis. The 2, 6-dimethyl-pyrazine and 3-(methylthio)-propanal was identified as the most intense aroma-active compounds of Jinhua ham due to their high log 2 (FD-factor) and characteristic aroma.

Prickly ash ( Zanthoxylum bungeanum Maxim) seed protein was hydrolyzed with papain to obtain hydrolysates with inhibitory activity against angiotensin-I converting enzyme (ACE). ACE inhibitory peptides (ACEIPs) were successfully purified from seed protein hydrolysates through ultrafiltration and gel chromatography. In vitro ACE inhibitory assay revealed an IC 50 value of 0.032± 0.008 mg·mL −1 for a component with <5 kDa molecular weight. Four fractions were isolated by Sephadex G-25 gel chromatography under the following elution conditions: flow rate, 0.6 mL·min −1 ; initial volume, 2.0 mL; and sample concentration, 30 mg·mL −1 . The second fraction showed the highest inhibitory activity with an IC 50 value of 0.021±0.007 mg·mL −1 . The stability of the ACE inhibitory activity of the obtained ACEIPs was identified under storage conditions with varied temperature, pH, and gastrointestinal protease digestion. Peptides derived from prickly ash seed protein hydrolysates may be a potential resource for exploring functional food or pharmaceuticals against hypertension.

Defatted hazelnut flour (DHF) in different levels (5 %, 10 % and 15 %) of locust bean, guar and xanthan gum were added in rice-based gluten-free formulations to improve rheological properties of dough and baking properties of bread. The rheological characteristics of dough samples were determined by steady flow curves and dynamic tests. The baking properties of breads were evaluated by specific volume, Textural Profile Analysis (TPA) parameters and color values. The rheological measurements showed that all gluten-free dough had pseudoplastic behavior. Specific volume values of breads ranged from 2.20 to 2.83 cm 3 /g. Gum addition enhanced the specific volume of gluten-free breads. Hardness values of gluten-free breads ranged from 1,069.80 to 3,135.88 g and DHF addition of gluten-free formulations caused significant decrease of the hardness values of breads ( p < 0.05). DHF addition in gluten-free formulations made bread crumb darker than bread without DHF and gum. DHF addition also increased a and b values of gluten-free bread’s crumb.

The diversity and nutritional value of the gluten-free products is challenging because of the increasing segment of population with celiac disease. In order to address this issue, the effects of different proteins (powdered eggs, soy, lupin, sodium caseinate and whey) to the gluten-free formulation based on rice and maize flours were assessed. The dough hydration was varied from 55 to 105 %, and dough rheological properties and bread characteristics were tested. The nature of the proteins and water level added to the gluten-free bread recipes has a decisive role on product quality. The best results in terms of rheological behavior were recorded for samples with powdered eggs, soy and lupin protein addition, at water absorption of 95–105 %. Concerning the bread quality, our results showed that protein addition to the rice and maize flours gluten-free formulations allows the improvement of crumb texture.

The effect of using four plasticizers namely ethylene glycol, propylene glycol, glycerol and sorbitol on mechanical and water barrier properties of transglutaminase cross-linked zein–oleic acid composite films was investigated. Results revealed that both mechanical and water barrier properties of the films were significantly affected ( p <0.05) by plasticizer type. Tensile strength (TS), water vapour permeability (WVP) and solubility (SB) values were all better in ethylene glycol control plasticized films compared to other plasticizers. Furthermore, irrespective of plasticizer type, transglutaminase treatment improved TS while when oleic acid was incorporated into the films in the range of 1–4% based on zein weight, the mechanical and water barrier properties of the composite film were diversely affected. Results from scanning electron microscopy for the 2% oleic acid-incorporated composite films revealed a rough and irregular surface morphology for the sorbitol plasticized films. Overall, ethylene glycol provided better mechanical and water barrier properties.

In the present research, a strain of Lactobacillus plantarum TK9 was isolated from the Chinese naturally fermented congee and its characteristics for probiotic and food preservation were investigated. In terms of probiotic, the strain not only survives bile salts and simulated gastric juice but grows well under hypertonic conditions. Besides, the L. plantarum TK9 exhibited a broad antifungal spectrum, including most of the species closely related to food spoilage, like Penicillium roqueforti , Penicillium citrinum , Penicillium oxalicum , Aspergillus fumigatus , Aspergillus flavus and Rhizopus nigricans . But no evident inhibition effect was found on Aspergillus niger . To further evaluate its potential as bio-preservative, L. plantarum TK9 was inoculated into citrus, apples and yogurt prior to the addition of moulds. The results indicated that L. plantarum TK9 could obviously prolong shelf life of the test food for 72–96 h and represent an excellent candidate for food-related bio-preservative.

In this study, oxidative stability of date-pits (i. e. Khalas variety) was investigated during storage as a function of temperature. The stability of date-pits oil was determined by measuring acid value (AV), peroxide value (PV), p -anisidine value (PAV), tocopherol and oxidative stability index. Initial characteristics of oil were assessed by measuring its physico-chemical and melting characteristics, fatty acids composition and aflatoxin. Storage of date-pits caused highest reduction in linoleic acid (C 18:2 , ω6) followed by oleic acid (C 18:1 , ω9). AV, PV and PAV of the fresh oil were 1.41 mg KOH/g oil, 3.30 meq/kg oil and 0.60, respectively. These values increased linearly at slower rate in the case of 30 °C storage, while sharp rise was observed after 40 days in cases of 100 and 150 °C storage ( p < 0.05). The results of this study indicate that date pits oil had a good oxidative and thermal stability and could thus be used to develop value-added food ingredients.

Gac fruit ( Momordica cochinchinensis L.) pulp is high in carotenoids and fiber; however, it is discarded during process. Both maturity stages of matured gac fruit could be used in the drying experiments. Gac fruit pulp was dried by different drying methods including tray drying (40–60 °C), heat pump-assisted dehumidified drying (40–60 °C), microwave drying (450–900 W), mixed-mode solar drying and freeze drying. The Modified Henderson model presented the best fit of desorption isotherms. New model proposed was the best drying model. Quality evaluation by β-carotene, lycopene, lutein, total phenolics and antioxidant activity revealed that heat pump-assisted dehumidified drying at 60 °C provided the highest lutein, total phenolics and antioxidant activity and could reduce drying time by 25 % and increased lutein, total phenolics and antioxidant activity by 12.6 %, 32.0 % and 0.3 %, respectively and is more promising drying method for gac fruit pulp.

Mantou (steamed bread) is a Chinese fermented wheat product that is cooked in steamer. Whole wheat flour (WWF) is healthier than regular wheat flour (WF). This study investigated the physicochemical properties of dough and mantou made from WF and/or WWF. Results showed that the substitution of WF by WWF resulted in stiffer and less extensible dough. Both Peleg–Normand and Wiechert models fitted well to the stress relaxation data of mantou. Increasing the substitution level of WWF led to the decrease of k 1 and k 2 in Peleg–Normand model as well as λ 1 and λ 2 in Wiechert model. Mantou with 100 % WWF had significantly higher hardness but lower cohesiveness and specific volume than regular mantou. However, free and bound phenolics and DPPH radical scavenging capacity of mantou obviously increased with the amount of WWF. Mantou with 25 % WWF had the highest overall sensory score among all mantous tested.