Food Technology
Hosein Ghavami; Azin Nasrollah zadeh
Abstract
Introduction
All the different species of hazelnut trees produce edible nuts. Hazelnuts are one of the most nutritious nuts, with a protein content of about 12%. They are also a good source of energy, with a fat content of about 60%, and an excellent source of carbohydrates, half of which are ...
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Introduction
All the different species of hazelnut trees produce edible nuts. Hazelnuts are one of the most nutritious nuts, with a protein content of about 12%. They are also a good source of energy, with a fat content of about 60%, and an excellent source of carbohydrates, half of which are dietary fiber. Hazelnuts also contain minerals (Ca, Mg, P, K), vitamins (E and B), and antioxidants. Hazelnut kernels may be eaten raw or roasted. Roasting alters and significantly enhances the color, texture, and appearance of nuts. These changes increase the overall palatability of the nuts and are mainly related to non-enzymatic browning. Non-enzymatic browning, however, causes a decrease in nutritional value due to decrease in protein digestibility and loss of essential amino acids. The most widely used nut roasting method is the convective heat transfer process, which is performed in a hot air oven working either in continuous mode or in batch systems. Therefore, modifying this process for improving product quality is very important. Color is among the most important quality attributes of dehydrated foods for consumers. Empirically, color is also an effective quality indicator because the brown pigments increase as the browning and caramelization reactions progress. Therefore, this study aimed to investigate the effect of high roasting temperature and storage time on color changes and oxidation of hazelnut paste oil.
Materials and Methods
After getting hazelnut kernels, the Roasting process was performed with hot air at 130 and 170 ℃ for 20 minutes. Hazelnut paste is produced as practiced in the industry. Quality analysis was roasted hazelnut paste color changes and fat oxidation. L *, a *, b * color index, (∆E), acidity, and peroxide value were measured in three intervals (0, 10, 30 days’). All experiments were performed in three replications. Average Data was compared using one-way ANOVA and done by SPSS version 21.
Results and Discussion
The main purpose of roasting is to improve the flavor, the color, and the crispy and crunchy texture of the product. The roasting process is very important to determine the characteristic roasted flavor and color of the product: in particular, temperature modulation is an important independent variable significantly affecting the quality features of hazelnut. In this study, ANOVA analysis results showed a significant difference between the treatments. Both roasting temperature and storage time affect the acidity and peroxide value. The increased temperature and storage increased the acidity and peroxide index, which indicated fat oxidation at higher temperatures. For ten days, the sample's peroxide value increased. After that, these parameters decreased because the first autoxidation products changing to the second product. Due to the release of free fatty acids after the basic hydrolysis of triglycerides, the acidity of the samples increased. The Browning color of roasted products was desirable. Discoloration during the roasting process of hazelnut kernels is mainly related to non-enzymatic browning. The brown pigments increase with the development of browning reactions. Results showed that the color index includes the L*, a*, b*, and ∆E values of the samples only affected by roasting temperature. With increasing the temperature, the L* value decreased but other values increased. Color indicators significantly changed and are not desirable for the consumers. The rate of color changes increased, including browning, indicating a non-enzymatic browning reaction in the samples during roasting.
Conclusion
According to the results, hazelnuts roasted at 130℃ introduced as the best treatment. It is recommended that the storage time does not exceed ten days.
Reza Farahmandfar; Somayeh Salmani; Hoda Fahim
Abstract
Introductıon: Nuts are one of the major resources of bioactive compounds such as tocopherols, tocotrienols, sterols (Jensen and Lauridsen, 2007). Tocopherols include 8 natural homologues that all of them belongs to vitamin E group (Chun, 2002). It is well known that vitamin E has good antioxidant activity ...
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Introductıon: Nuts are one of the major resources of bioactive compounds such as tocopherols, tocotrienols, sterols (Jensen and Lauridsen, 2007). Tocopherols include 8 natural homologues that all of them belongs to vitamin E group (Chun, 2002). It is well known that vitamin E has good antioxidant activity and among its isomers, α-tocopherol and γ-tocopherol have highest biological activity and free radical scavenging, respectively (Grilo et al., 2014). In recent years, the beneficial health effects of vitamin E on some disease such as cancer and heart disorders attract researcher’s attentions (Wagner et al., 2004).Roasting process changes the chemical and nutritional properties of nuts, including antioxidants, vitamins, colors, and aroma mostly through Maillard reaction (Alamprese et al., 2009; Ballistreri et al., 2009). Due to the importance of vitamin E antioxidant activity and its heat sensitivity, the residual amounts of them after different roasting conditions were investigated. Materials and methods: Samples were spreaded in alominum foil and placed in forced air oven at 120 and 150 ºC and different time intervals including 0, 20, 30 and 40 min. After roasting, samples were powdered, then 0.5 g of each sample plus 0.05 g ascorbic acid were added to 0.5 mL ethanol (90.2%) and 0.5 mL KOH and mixed in a tube (16× 125 mm). The tube was then placed in water bath for 30 min. Then, the tube were placed in ice bath for 5 min, then 3 mL deionized water, 5 mL hexane were added to the tube and vortexed for 30 s and centrifuged for 10 min at 1000 rad/s at ambient temperature. The extraction was done twice. Hexane layer evaporated with nitrogen then 1 mL of mobile phase added to tube and vortexed again. Prepared samples then were injected to HPLC (Knuer- Germany). Results and discusion: Based on the obtained results, α-tocopherol content in almond was more than γ-tocopherol. After 20 and 30 min of roasting, at 150 and 120 ºC respectively, the amount of α-tocopherol slightly increased, while it decreased with increasing roasting time. γ-tocopherol content in almond at both temperatures also increased up to 20 min roasting and decreased till the end of process. In hazelnut, at both temperatures up to 20 min and then decreased till end of roasting process. This trend was shown for peanut tocopherols as well. With increasing in roasting time, α-tocopherol and γ-tocopherol content decreased to their initial level. It has suggested that tocopherols which attached to the other components such as phospholipids released more conveniently under thermal treatment like roasting which leads to increase their concentrations at initial of thermal process. In pistachio, 150 and 120 ºC respectively caused to increase in γ-tocopherol content, respectively while its content decreased up to the end of roasting time (40 min). α-tocopherol content at both temperatures increased after 20 min, then decreased gradually as time passes. Results indicated that both time and temperature of roasting had a significant effect on α- and γ-tocopherol of four nuts. Although both of temperatures in our study significantly on increased vitamin E isomers at the start of roasting process, their contents decreased with increasing in roasting time. Maximum amount of both isomers were detected at 120 ºC after 30 min and at 150 ºC after 20 min.
Feresshteh Gholami; Sara Ansari
Abstract
Introduction: Roasting is an essential process that improves the taste, color, texture and appearance of the product. The shelf-life is also extended as a result of roasting. The temperature and the duration of roasting are the most important factors that influence favorable traits. IR is a novel technique ...
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Introduction: Roasting is an essential process that improves the taste, color, texture and appearance of the product. The shelf-life is also extended as a result of roasting. The temperature and the duration of roasting are the most important factors that influence favorable traits. IR is a novel technique for roasting that, compared to conventional heating, has positive advantages such as shorten heating time, significant energy saving and uniform heating. This study aimed to investigate the effect of IR, compared to conventional, roasting on some physicochemical and quality properties of soybeans. Moreover, the conditions of roasting soybeans via the two mentioned methods were optimized using Response Surface Methodology (RSM).
Material and methods: Soybean seeds were collected from a commercial farm in Gorgan (North of Iran) and were dried in an oven at 40 °C for 48 hours until the moisture content became lower than 5 % w/w. For each treatment, 25 g of raw soybeans were spread in glass petri dishes and were then roasted under the conditions selected for each experiment. In conventional roasting an electrical oven with the temperature range of 180 to 260 °C and time duration of 5 to15 min was used. IR roasting was performed using an IR-warm air apparatus with a constant power of 1300 W at the air temperature of 180-240 °C for 5-15 min. After the temperature equilibrium was reached, the samples were packed in polyethylene bags and were kept at 4 °C until further analysis. For each roasting method, a central composite design consisted of two variables of time and temperature (each in three levels) and a total of 13 experiments were applied. Response surface analysis was performed using Design-Expert software. The moisture content of samples was determined by drying the samples in a drying oven at 105 °C until a constant weight was reached. The total phenol content was measured quantitatively by the Folin-Ciocalteu colorimetric method based on the reaction of reagents with the active hydroxyl groups of phenolic compounds. The radical scavenging activity of the samples was determined by the DPPH radical. The force needed to break the roasted seeds was evaluated using a texture analyzer equipped with a load cell of 25 Kg. The color of samples was evaluated in a special box under controlled conditions (in terms of light intensity and camera position) using a digital camera and the color parameters (L*, a* and b*) and the color change (ΔE) were determined.
Results and Discussion: According to the results, the second- and first-order models were suggested for the study of time and temperature effects on moisture reduction that were both significant (p<0.05). In two methods, total phenolic content and antioxidant activity models were significantly (p<0.05) second-order. With increasing time and temperature, these above values increased. Hardness and color differences of oven roasting were both first-order but only color differences were first-order for infrared roasting. Effects of two parameters were significant in all models. Optimum conditions for soybeans roasting sing oven and infrared were 223°C – 13 min and 231°C – 11 min, respectively. In optimum condition, experimental data for the moisture content, total phenolic content, antioxidant activity, hardness and color differences were: (1.10, 4.53, 42.75, 9.03, and 4.93) , (1.58, 4.93, 47.85, 6.20, and 4.79) respectively. Based on above results, infrared can be introduced as a replacement of conventional oven method for the roasting of soybeans.
Hadi Bagheri; Mahdi Kashani-Nejad; Mehran Alami; Aman Mohammad Ziaiifar
Abstract
Introduction: Roasting is one of the processing steps involved in the nut industry to improve the flavor, color, texture and overall acceptability of the product. Ppeanut is a fruit or pod of the order Leguminosae and contains 47–50% oil, 25–30% protein and is an essential source of minerals and ...
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Introduction: Roasting is one of the processing steps involved in the nut industry to improve the flavor, color, texture and overall acceptability of the product. Ppeanut is a fruit or pod of the order Leguminosae and contains 47–50% oil, 25–30% protein and is an essential source of minerals and vitamins; thus it makes a substantial contribution to human nutrition. Peanuts are readily acceptable as a cheap protein source and popular snack item that can be eaten alone or combined with other foods. Recently, peanuts have gained much attention as functional food and roasted peanuts is one of the most popular snack foods, in which roasting is a key step in the process and directly impacts the quality (crispness, taste, and flavor) and shelf-life of the final product. Understanding of the roasting process is of interest because roasting is a critical processing step not only for peanuts, but many other food products such as coffee, cocoa, grains and other tree nuts. Roasting is a process to develop color, flavor and textural characteristics of product through chemical reactions, therefore proper roasting is critical to flavor and texture development as well as nutritional content of the final product.
Materials and methods: In this study, dried Goli peanuts were supplied from a local market in Minodasht, Iran in 2015 and stored at 4°C until processing. The average moisture content of peanut kernels was measured as 5.1 % (d.b.). Kernels were sorted manually to get the uniform sizes for roasting. 100 g peanut kernels were soaked in 500 ml of 25% salt solution for 30 min. After soaking, the salt solution was drained using a strainer and the excess water was removed by a cloth filter. After soaking, the moisture content of soaked peanut kernels increased to 8.27 % (d.b.). For roasting, three temperatures (140, 160 and 180°C) and three times (10, 20 and 30 min) and constant air velocity (1 m/s) were applied. Roasting was performed in a hot air roaster equipped with a controller to adjust the roasting temperature. After roasting, the whole kernels were allowed to cool at room temperature (23 ± 2°C). Roasting process was performed in 3 replications. Instrumental texture measurements (Uniaxial compression test) were carried out at room temperature using a TA-XT Plus Texture Analyzer using cylinder probe (diameter 25 mm) on peanut halves. The textural parameters of peanut halves were expressed as fracture force (initial peak or first fracture force (N)), hardness (highest peak compression force (N)), initial tangent modulus or apparent modulus of elasticity that shows sample rigidity in the linear part of the force-deformation curve (N/m) and compressive energy or area under the curve for the compression that is the work (N×m) required to attain deformation, indicative of internal strength of bonds within product. Sensory attributes including colour, texture, flavor, odour, total acceptance and final acceptance were assessed according to a five-grade hedonic scale (5 points – the best, 1 point – the worst). A completely randomized factorial design was used to evaluate the results and analysis of variance (ANOVA) was carried out to compare the mean values. All significant differences were reported at P ≤ 0.05 levels. Minitab statistical software (Minitab Release 16, Minitab Inc., USA) was used for all statistical analyses in the present research. However, MSTATC (Version 2.10, Michigan State University) was used to determine significant differences.
Results & discussion: Roasting is one of the most important steps in peanuts processing that leads to the development of the desired aroma, taste, texture and color of the final product. The results showed that increasing the roasting temperature and time decreased the fracture force (75.19–45.92 N), instrumental hardness (81.74–48.90 N), apparent modulus of elasticity (7.508-5.446 N/s), compressive energy (469.0–199.1 N.s) and improved the sensory characteristics of peanut kernels. During roasting process, moisture content of peanut kernels decreased and they became more crumble and fragile which causes to break easier and moisture reduction helps to create a desirable crisp texture. The results of the consumer test showed that the roasted peanut kernels have good acceptability for color (4.50), texture (4.15), flavor (3.89), odor (4.05), total acceptance and final acceptance (3.97) on roasting temperature and time (160°C and 30 min). The results obtained for VIP coefficients (standard coefficients) in PLS regression for fracture force, instrumental hardness; apparent modulus of elasticity and compressive energy variables indicated that apparent modulus of elasticity could be able to predict the individual sensory attribute of peanut kernels except color. PLS results showed that apparent modulus of elasticity could successfully predict quality sensory characteristics of peanut kernels. Thus, instrumental apparent modulus of elasticity could be replaced with sensory analysis for evaluation the quality of peanut kernels.
