Food and Bioprocess Technology (v.4, #7)

Editorial Message from the Editor-in-Chief by Da-Wen Sun (1127-1127).

This study examined the use of pilot-scale radio frequency (RF) heating for thawing beef meat blends (lean, 50:50 lean/fat and fat). The aim was to thaw blocks (4 kg) to within a target temperature range of −1 to +5°C. Post-thawing temperature distribution in the blocks was compared to that of blocks thawed by conventional air thawing. The optimum RF conditions for thawing lean meat was 35 min of RF heating delivered in a noncontinuous fashion (20 min on, 10 min off, and followed by 15 min on) at 400 W, which gave a mean temperature of 0.2°C (SD 1.8). By comparison, conventional thawing was achieved in 50 h 20 min which represented an 85-fold difference in thawing time. Comparable uniformity of temperature distribution was obtained by each method. For the lean/fat mixture and 100% fat, the target range could not be achieved due to problems of runaway heating. The latter phenomenon relates to the manner in which the absorbed energy is transferred throughout the material as influenced by the thermophysical properties of the product.
Keywords: Radio frequency; Thawing; Beef

Free Radical Scavenging Activity of Aqueous and Ethanolic Extract of Brassica oleracea L. var. italica by Abdul Mueed Bidchol; A. Wilfred; P. Abhijna; R. Harish (1137-1143).
In this study, antioxidant activities of aqueous and ethanolic extracts of Brassica oleracea L. var. italica were investigated. The antioxidant properties of both extracts of Brassica oleracea L. var. italica were evaluated using different antioxidant tests, including 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging, superoxide radical scavenging, inhibition of microsomal lipid peroxidation, reduction of power, and metal ion chelating activities. Inhibition of superoxide scavenging by aqueous and ethanolic extracts showed an IC50 of 0.93 and 0.25 mg/ml, respectively. Metal ion chelation showed an IC50 of 0.35 mg/ml of both the extracts and was equipotent to positive control, ethylenediamine tetra-acetic acid. The ethanolic extract of Brassica oleracea L. var. italica exhibited higher antioxidant activity in DPPH radical and superoxide anion scavenging than that of aqueous extract. The results obtained in the in vitro models clearly suggest that, Brassica oleracea L. var. italica is a natural source for antioxidants, which could serve as a nutraceutical with potential applications in reducing the level of oxidative stress and related health benefits. However, comprehensive studies need to be conducted to ascertain the in vivo safety of such extracts in experimental animal models.
Keywords: Brassica oleracea L. var. italica ; Antioxidant activity; Reactive oxygen species; Lipid peroxidation; Metal ion chelation

Antioxidant Activities of Rapeseed Protein Hydrolysates by Mu Pan; Tong S. Jiang; Jun L. Pan (1144-1152).
Rapeseed protein hydrolysates (RPH) were obtained by enzymatic hydrolysis of rapeseed protein using Alcalase 2.4 L FG. The degree of hydrolysis (DH) of RPH was about 25% using pH-stat method. The antioxidant activities of RPH were investigated by employing several in vitro assay, including the 1,1-diphenyl-2-picrylhydrazyl (DPPH)/superoxide/hydroxyl radical scavenging assays, and reducing power assay. RPH showed scavenging activity against free radicals such as DPPH, superoxide, and hydroxyl radicals. The radical scavenging effect was in a dose-dependent manner, and the EC50 values for DPPH, superoxide, and hydroxyl radicals were found to be 0.71, 1.05, and 4.92 mg/mL, respectively. In addition, the RPH also exhibited notable reducing power, which was 0.51 at 2.00 mg/mL. The data obtained by in vitro systems obviously established the antioxidant potency of RPH. Combined with the results of the amino acid profiles, RPH were believed to have high nutritive value in addition to antioxidant activities.
Keywords: Rapeseed protein hydrolysates; Antioxidant activities; Nutritive value

Lipase-catalyzed enrichment of rice bran oil with n-3 fatty acid in order to obtain a structured lipid containing essential fatty acids has been optimized by response surface methodology. In this process, α-linolenic acid was used as an acyl donor using lipase-catalyzed acidolysis in hexane in presence of immobilized lipase from Rhizomucor miehei. The effect of incubation time and temperature, enzyme concentration and substrates mole ratio and their complex interaction on percentage incorporation of n-3 fatty acid, ratios of saturated fatty acid to polyunsaturated fatty acids, monounsaturated fatty acids to polyunsaturated fatty acids and n-6 to n-3 (18:2 to 18:3) fatty acids have been studied using a central composite rotatable design of experiments. The results showed that at the optimum conditions such as reaction time 4.5 h and reaction temperature 37. 5°C, substrate ratio ranging from 1.0 to 1.9, enzyme concentration varying from 1.0% to 2.0% are needed to fulfill the conditions such as percentage incorporation of n-3 fatty acid ≤18%, ratio of saturated fatty acid to poly unsaturated fatty acid ≥0.42, ratio of mono unsaturated fatty acid to poly unsaturated fatty acid ≥0.8, and ratio of n-6 to n-3 ≥1.30.
Keywords: Enzymatic acidolysis; Lipase; Rhizomucor miehei ; Rice bran oil; α-Linolenic acid; Response surface methodology

The effects of the blanching process of sweet corn on shearing stress, shearing energy, and processing recovery of kernels as well as weight and dry substance of kernels and cobs were studied. Sweet corn cobs were blanched in water, where blanching time ranged from 2 to 8 min and temperature ranged from 75 to 100 °C. Nonblanched cobs (fresh cobs) were used as control samples. It was found that all analyzed variables were significantly affected by blanching time and temperature. The average values of all analyzed variables, except moisture which decreased, increased with increasing of the blanching time and temperature. Changing the blanching time and temperature affected the dry substance of kernels and cobs, kernel and cob mass, recovery processing by increasing it, as well as the average values of shearing stress and shearing energy by decreasing them.
Keywords: Sweet corn; Blanching; Shearing stress; Shearing energy; Processing recovery; Weight; Dry substance

Quality Characteristic and Shelf Life Studies of Deep-Fried Snack Prepared from Rice Brokens and Legumes By-Product by Uma Tiwari; Mary Gunasekaran; R. Jaganmohan; K. Alagusundaram; B. K. Tiwari (1172-1178).
Legumes and cereal by-product flours were formulated into six of deep-fried snacks, which were evaluated for their physicochemical and sensory properties. Shelf life was analyzed for chemical parameters including: moisture gain, free fatty acid (FFA), and peroxide value (PV) at time intervals of 5 days along with organoleptic evaluation at the beginning and after 5, 10, 15, 20, 25, and 30 days of storage at room temperature (29 ± 2.0 °C) and relative humidity (67 ± 2.5%). A strong negative correlation (−0.83) was observed between the bulk density and the expansion ratio of the products. During storage moisture gain, FFA and PV increased linearly (R 2 > 0.92). The results of organoleptic evaluation of all six fried snacks showed that there was no consistent pattern for sensory attributes. The maximum shelf life of the products was 24 days under the storage conditions studied.
Keywords: By-products; Free fatty acid; Peroxide value; Snacks

Optimum Blend of Chitosan and Poly-(ε-caprolactone) for Fabrication of Films for Food Packaging Applications by C. Swapna Joseph; K. V. Harish Prashanth; N. K. Rastogi; A. R. Indiramma; S. Yella Reddy; K. S. M. S. Raghavarao (1179-1185).
The present work deals with the preparation and characterization of the chitosan and poly-ε-caprolactone (PCL) solution-casted blended films in various proportions (chitosan–PCL ratio 90:10, 80:20, and 70:30). The films were casted and dried at 55 °C, which were characterized based on the mechanical, barrier, thermal, and microscopic properties. The film prepared from chitosan to PCL ratio 80:20 resulted in increase percentage elongation by 20.56% as compared to pure chitosan film. Fourier transform infrared spectrum indicated a shift in peak of absorption from 1743.9 to 1724.8 cm−1 due to carbonyl group of PCL indicating the miscibility and interaction between the PCL and chitosan. Scanning electron microscopy revealed that PCL appeared as a co-continuous phase with chitosan for ratio 80:20, confirmed the interaction between chitosan and PCL. The above study indicated that the properties of chitosan films can be modified with the addition of PCL and may find its versatile use in food packaging.
Keywords: Chitosan; Polycaprolactone; Polyester blends; Biodegradable polymer; Film properties; DSC; FTIR

Improved Glucoamylase Immobilization onto Calcined Chicken Bone Particles by Cecilia Carpio; Francisco Batista-Viera; Jenny Ruales (1186-1196).
Calcination was considered for the first time as an alternative to recover inorganic bone component from spent glucoamylase-bone derivatives. The subsequent adsorption of glucoamylase (GA) onto calcined bone particles was assessed. Adsorption capacity of the calcined matrix was found to be from 1.1- to 1.4-fold superior to that of non-calcined supports, and it was dependent on the applied load. Moreover, the expressed activity of GA derivatives on calcined matrix was, at least, 2-fold higher than that of biocatalysts onto non-calcined support. The optimization of the loading allowed the preparation of derivatives with 139 GA units per gram of support, which preserve 52% of the immobilized activity. Additionally, calcination of spent GA biocatalysts on calcined bone particles was performed, and adsorption of glucoamylase onto the bone particles calcined a second time was also found to be efficient. In addition to the improved catalytic properties, the half-life at 55°C of the GA biocatalysts on calcined bone was increased 1.7-fold in comparison with that of soluble GA and GA adsorbed onto non-calcined bone particles. Furthermore, the same cassava starch conversion can be achieved batchwise in a stirred-tank reactor using less insoluble biocatalyst, 37% of the GA-bone derivative, which represents an important saving for industrial applications.
Keywords: Calcination; Chicken bone; Glucoamylase immobilization; Pyrolysis; Support recovery

The objectives of the present work were to optimise watercress heat and thermosonication blanching conditions, in order to obtain a product with better quality for further freezing, and to evaluate the effects of thermosonication on the microstructure of watercress leaves. In a chart of optimal time–temperature conditions for a 90% peroxidase inactivation (imposed constraint), vitamin C (objective function) and a-value (improvement toward green) were mathematically predicted for both heat and thermosonication blanching treatments. Two optimal thermosonication combinations were selected: 92 °C and 2 s, retaining 95% of vitamin C content and 5% a-value improvement, and a better condition in terms of practical feasibility, 86 °C and 30 s, allowing a 75% vitamin C retention and 8% a-value improvement. The experimental values, for each thermosonication optimal time–temperature zone, were in good agreement with the models' predicted responses. In terms of microstructure, thermosonicated watercress at 86 and 92 °C showed similar loss of turgor and release of chloroplasts. The proposed optimal thermosonication blanching conditions allow the improvement of the blanched watercress quality and consequently contribute for the development of a high-quality new frozen product. However, a suitable scale-up is mandatory for industrial implementation.
Keywords: Watercress; Thermosonication; Optimisation; Peroxidase; Colour; Vitamin C; Microstructure

Optimization of Conditions for Enzymatic Production of ACE Inhibitory Peptides from Collagen by Qing Kong; Feng Chen; Xi Wang; Jing Li; Bin Guan; Xingqiu Lou (1205-1211).
Enzymatic condition for producing angiotensin I-converting enzyme (ACE) inhibitory peptides from collagen was optimized with the aid of response surface methodology, which also derived a statistical model for experimental validation. The results showed that the optimal condition for the hydrolysis by pepsin was at pH 2, temperature 37 °C, and in enzyme to substrate ratio (E/S) of 2 when 8.23% collagen (w/v) and 3.82 h of hydrolysis time were applied. Through the single-enzyme hydrolysis, the ACE inhibitory activity could reach an average of 78.06%. In contrast, when a combination of pepsin and trypsin was used for a multiple-proteases hydrolysis, the ACE inhibitory activity could be significantly improved to an average of 88.25%. Furthermore, the IC50 (μg/mL) value of the enzyme combination by pepsin and trypsin (141.64 ± 22.11) was significantly lower than that of the combinations of pepsin and papain (438.59 ± 84.37) or pepsin and protease M (336.76 ± 87.88; p<0.05). Our results have shown that collagen can be used for enzyme-mediated production of ACE inhibitory peptides.
Keywords: Angiotensin I-converting enzyme; Antihypertensive effect; Collagen; Fractional factorial design (FFD); Central composite design (CCD); Response surface methodology (RSM)

Experimental values of volume and area changes for sweet (Prunus avium) and sour (Prunus cerasus) cherry and rose hips (Rosa rubiginosa) measured in previous works were analyzed to propose generalized correlations for the three fruits which predicted with low errors. The correlation developed is lineal and the highest errors were observed for fruit water contents corresponding to storage stability values. The shape factors were measured for the fruits, which were close to spherical values as the fruits dried. This would enable the assumption of spherical shape to calculate characteristic dimensions used in modeling. Moreover, the predictions of kinetic models were compared with experimental data for three radii: the initial, assumed constant; variable, estimating the radius with the correlations published for each fruit; and variable, calculating the radius with the generalized correlation developed in this work. The RMSE between the experimental data and the predictions by the kinetic model were between 0.321 and 0.562; 0.021 and 0.111; and 0.020 and 0.093, respectively.
Keywords: Shrinkage; Modeling; Variable radius; Shape factor; Equivalent diameter

An optimized microwave-assisted extraction (MAE) method was developed for extracting secoisolariciresinol diglucoside (SDG) from flaxseed. This paper presents the optimization of factors for maximizing the extraction yield of SDG. This work was conducted using the experimental domain identified in a previous study by means of screening designs, that is, samples of 1 g defatted flaxseed meal (DFM) were extracted with 50 ml NaOH of concentration of 0.5–1 M, at microwave power levels of 60–360 W, for 3–9 min, with the microwave power applied intermittently (power on 30 s/min) and continuously (power on 60 s/min). The MAE of SDG was maximized when 1 g DFM was extracted with 50 ml 0.5 M NaOH, at 135 W, for 3 min in intermittent power mode (power on 30 s/min). The optimized MAE achieved a 6% increase in the extraction yield (21.45 mg SDG per gram DFM) as opposed to a direct hydrolysis method (20.22 mg SDG per gram DFM). The MAE of SDG was governed by the microwave–NaOH interaction, which had a curvilinear dependence on the microwave power level, and linear dependence on the NaOH concentration. The microwave-induced effects accounted for a 10% increase in the SDG extraction yield (21.45 mg SDG per gram DFM) as opposed to a microwaveless control method (19.45 mg SDG per gram DFM). The optimized MAE method has good repeatability, a 97% recovery of the target compound; it is fast and efficient and can be used for precise quantification of SDG in flaxseed.
Keywords: MAE; SDG; Flaxseed; Lignan; Phytoestrogen; Response surface; Optimization; Central composite design

Effect of Surface Density on the Engineering Properties of High Methoxyl Pectin-Based Edible Films by Tiziana Giancone; Elena Torrieri; Prospero Di Pierro; Silvana Cavella; Concetta V. L. Giosafatto; Paolo Masi (1228-1236).
The effect of pectin surface density (ρ s) on the engineering properties of high methoxyl (HM) pectin-based edible films was determined in order to explore the role of ρ s on structure and functional properties. Films at different ρ s values (2.5, 3.2, 3.8, 4.5, 5.1, 5.8 mg cm−2) were analyzed by means of microscopy, thermal, mechanical, and barrier (water vapor permeability WVP, oxygen permeability $$ { ext{kP}}_{{{ ext{O}}_2 }} $$ , carbon dioxide permeability $$ { ext{kP}}_{{{ ext{CO}}_2 }} $$ ) properties. Microscopy, thermal, and mechanical results showed that by increasing ρ s from 2.5 to 5.8 mg cm−2, the film structure does not change. HM pectin-based film has a tensile strength of 20 ± 7 MPa and an elastic modulus (E) equal to 2,400 ± 200 MPa. However, it is quite brittle as the elongation to break (e) is close to 1%. Although the film structure was unaffected by ρ s, WVP increased with the rise in ρ s while $$ { ext{kP}}_{{{ ext{O}}_2 }} $$ and $$ { ext{kP}}_{{{ ext{CO}}_2 }} $$ decreased. On the whole, HM pectin-based film showed barrier properties comparable to biodegradable commercial film and low selectivity.
Keywords: Edible films; HM pectin; Mechanical; Thermal; Barrier properties

A Study on Degree of Starch Gelatinization in Cakes Baked in Three Different Ovens by Ozge Sakiyan; Gulum Sumnu; Serpil Sahin; Venkatesh Meda; Hamit Koksel; Peter Chang (1237-1244).
The main objective of the study was to determine the effects of different baking ovens and different cake formulations on the degree of starch gelatinization during cake baking. Baking was performed in microwave, infrared–microwave combination, and conventional ovens. Starch gelatinization levels of fat free, 25% fat, and 25% Simplesse™-containing cake samples were examined using differential scanning calorimeter (DSC) and rapid visco analyzer (RVA). Both DSC and RVA results showed that increasing baking time increased gelatinization level for all baking types significantly. It was also found that the effect of fat content on starch gelatinization was different depending on the type of baking. Addition of fat reduced the degree of starch gelatinization in conventional baking. However, fat enhanced the gelatinization in microwave and infrared–microwave combination ovens. Usage of Simplesse™ as a fat replacer decreased the starch gelatinization in all types of baking significantly. There was insufficient starch gelatinization in microwave-baked cakes in which the degree of gelatinization ranged from 55% to 78% depending on formulation. On the other hand, it ranged from 85% to 93% in conventionally baked cakes. Combining infrared with microwaves increased degree of starch gelatinization (70–90%).
Keywords: Microwave baking; Gelatinization; Cake; DSC; RVA

Stability and Degradation Kinetics of Bioactive Compounds and Colour in Strawberry Jam during Storage by Ankit Patras; Nigel P. Brunton; B. K. Tiwari; Francis Butler (1245-1252).
The effect of storage time and temperature on degradation of bioactive compounds such as ascorbic acid, anthocyanins, total phenols, colour and total antioxidant capacity of strawberry jam were investigated. The results indicated that lightness (L) value decreased significantly (p < 0.05) over 28 days of storage at 4 and 15 °C, with lower values measured at higher temperatures. Anthocyanins, ascorbic acid and colour degradation followed first-order kinetics where the rate constant increased with an increase in the temperature. The reaction rate constant (k) increased from 0.95 × 10−2 day−1 to 1.71 × 10−2 day−1 at 4 and 15 °C for anthocyanins. Similarly, k increased from 2.08 × 10−2 day−1 to 4.54 × 10−2 day−1 at 4 and 15 °C for ascorbic acid. In general, total antioxidant activity for strawberry jam samples stored for 28 days at 4 and 15 °C exhibited lower values as compared to control (day 0). The results showed greater stability of nutritional parameters at 4 °C compared to 15 °C.
Keywords: Strawberry jam; Kinetics; Ascorbic acid; Anthocyanins; Colour

Although ohmic heating is used as an alternative heating method for liquid egg products commercially, there is a lack of information on the change of rheological properties and fluid dynamics characteristics of ohmically heated liquid whole egg in the literature. The change of rheological behaviour of the ohmically heated liquid whole egg, across a temperature range of 4–60 °C, was determined by using a concentric rotational viscometer. The ohmic heating was conducted by applying the voltage gradient (20 V/cm) at 50 Hz. The temperature dependency of the electrical conductivity of liquid egg was linear (R 2 = 0.999). The rheological behaviour was found to be shear thinning since power law model had higher regression coefficient and lower χ 2 and root mean square error values than Newtonian model. Ohmically heated liquid whole egg exhibited higher degree of thixotropic index indicating the occurrence of the protein denaturation at 60 °C. The flow behaviour of liquid whole egg in the continuous ohmic heating system was predicted as laminar (GRe range of 87.59–538.87) for the mass flow rate range of 0.0056–0.0166 kg/s. The friction factors and pressure losses in the system in those mass flow rates were also assessed. The result of this study will give necessary information on flow characteristics of liquid whole egg for the modelling, designing and the scaling up of the continuous ohmic heating systems for pasteurisation of liquid egg products.
Keywords: Ohmic heating; Liquid whole egg; Rheology; Fluid dynamics; Non-Newtonian fluid

This study developed a procedure for the production of sour bread from 100% maize meal. The modified method combined sponge and dough methods in two mixing stages to form a batter rather than stiff dough. The baking quality of the maize meal was improved by using starter cultures of lactic acid bacteria selected from indigenous micro-flora of the maize meal. Lactobacillus plantarum lowered the pH of fermenting maize meal (3.1) more than other starters; Lactobacillus brevis produced the highest amount of diacetyl (180.8 mg) while Leuconostoc mesenteroides recorded the highest final viscosity value of 144.0 RVU. The sour maize bread fermented with a mixed culture of the three selected cultures had the best physical (weight 122 g, height 3.7 cm, crumb dry matter 69%) and sensory properties (taste and overall acceptability 4.8 on a five-point hedonic scale), which were significantly different (P ≤ 0.05) from bread samples produced with other test starters). The mixed cultures are recommended for sour maize bread production for good rheological properties, proper acidification, and acceptable flavor development.
Keywords: Lactobacillus plantarum ; Lactobacillus brevis ; Leuconostoc mesenteroides ; Sourdough; Sour maize bread; Non-wheat bread

Mature green “Baxi” banana (Musa spp. AAA Group, Cavendish) fruits were harvested at 60% and 80% maturity stages. In order to evaluate the effects of harvesting at different maturity stages on storage quality and changes in sucrose-metabolizing enzymes, fruit firmness, disease index, contents of starch, and total soluble sugars were determined, and enzyme activities associated with sucrose metabolism was investigated under natural and accelerated (treated with ethylene) ripening conditions. In fruit treated with ethylene, changes in flesh firmness, total sugar content, starch content, disease index, and activity of sucrose phosphate synthase (SPS), sucrose synthase (SS), acid invertase (AI), and neutral invertase (NI) were accelerated dramatically compared with untreated fruit with both 60% and 80% maturity. When fruit ripened under natural conditions, the changes in firmness, disease index, starch content, total sugar content, SPS activity, SS, AI, and NI activity in fruit with 80% maturity were significantly faster than those in fruit with 60% maturity. On the contrary, when fruit ripened under accelerated conditions, no significant differences in firmness, sugar, starch, disease index, SPS, SS, AI, and NI were observed between fruit harvested at 60% or 80% maturity. It is suggested that storage quality and sucrose-metabolizing enzymes of banana fruit stored under natural conditions are related to harvest maturity stage; storage quality of fruit with lower harvest maturity is better than fruit with higher maturity. However, when fruit ripening is accelerated by ethylene, the harvest maturity stage has no influence on storage quality and changes in sucrose-metabolizing enzymes.
Keywords: Banana fruit; Harvest maturity; Storage quality; Sucrose-metabolizing enzymes

Effect of Drying on the Color of Tarragon (Artemisia dracunculus L.) Leaves by Akbar Arabhosseini; Sudhakar Padhye; Willem Huisman; Anton van Boxtel; Joachim Müller (1281-1287).
The effect of drying conditions on the color of tarragon (Artemisia dracunculus L.) leaves was studied. Tarragon leaves were dried at temperatures of 40 to 90 °C with a constant airflow of 0.6 m/s. The samples were collected at 7%, 10%, 20%, and 30% moisture content wet basis for evaluation of the color change. The color parameters of fresh and dried leaves were measured by a colorimeter. The individual parameters of L*a*b* and L*C*h° color systems were evaluated and h° proved to be the best parameter to monitor color change. The smallest change of the color parameters was observed at 40 °C, in which temperature was low, and also at 90 °C, when drying time was short. The biggest change occurred at the temperatures of 50 to 70 °C. Most of the color change happened before the material reaches 35% moisture content. The combination of drying time and temperature defines the change of color.
Keywords: Artemisia dracunculus ; Color; Drying; French Tarragon; Russian Tarragon

In this study, the mechanical properties of walnut (Juglans regia L.) cultivars were investigated as a function of moisture content. The experiments were carried out at three moisture contents, compression speeds (0.5, 1, and 1.5 mm/s), and compression axes (X-, Y-, and Z-axes). The highest rupture force and rupture power in all moisture contents were obtained for walnut cultivars loaded along the Y-axis. Rupture force, rupture energy, and rupture power of walnuts decreased in magnitude with an increase of moisture content, while rupture force, specific deformation, rupture energy, and rupture power increased with an increase of compression speeds. The highest rupture force was obtained with load along the Y-axis as 410.4 N and 394.3 N and also the highest rupture force was recorded at 1.5 mm/s compression speed as 260.7 N and 377.1 N for Yalova-1 and Yalova-3 cultivars, respectively. A linear force decrease was observed from 320.5 N to 196.4 N and from 492.7 N to 247.1 N with increasing moisture content from 11.46% to 23.16% and from 11.25% to 19.47% for Yalova-1 and Yalova-3, respectively. The highest rupture force, specific deformation, rupture energy, and rupture power were obtained at 1.5 mm/s compression speed, while the lowest rupture force was obtained at 0.5 mm/s compression speed for walnut cultivars. The lower rupture force and rupture power were obtained with load along Z-axis for Yalova-1 and Yalova-3 walnut cultivars. The results revealed that the higher compression speed and Z-axis could be recommended for cracking of shelled walnuts.
Keywords: Walnut varieties; Mechanical properties; Moisture content; Compression speed and axis

Influence of Whey Protein Addition and Feed Moisture Content on Chosen Physicochemical Properties of Directly Expanded Corn Extrudates by Mladen Brnčić; Tomislav Bosiljkov; Marko Ukrainczyk; Branko Tripalo; Suzana Rimac Brnčić; Sven Karlović; Damir Karlović; Damir Ježek; Dražen Vikić Topić (1296-1306).
Production of extrudates from cereals is an often-used technological process in today’s world food industry. Extrudates from corn flour produced using the twin-screw extrusion process and enriched with whey protein concentrate represent high-quality source of proteins and fats. Whey protein concentrate (WPC) as a valuable source of proteins and minerals is one of the highest-quality components for possible extrudate enrichment. In this paper, the influence of various WPC addition and some extrusion process parameters such as feed moisture content ( $$ Q_{{{ ext{H}}_{ ext{2}} { ext{O}}}} $$ ) on physicochemical properties of directly expanded corn flour extrudates manufactured in twin-screw co-rotating extruder was investigated. Whey protein concentrate was added in the following ratios 7.5%, 15% and 22.5% and water in 10.08, 12.18 and 14.28 L/h. Final composition of products is determined with measuring of protein, fat and water shares, water absorption index (WAI) and water solubility index (WSI). With added WPC and with increase of water volume flow, there was a significant rise in total protein, fat and water content in final products, as well as lowering of WSI and rising of WAI indexes. The statistical analysis of the obtained data shows that the lowest WSI and the highest WAI had samples with the largest share of WPC (22.5%) and water volume flow of 14.28 L/h. Colour is measured for each sample, and results were represented with hue angle (H), chroma (C) and lightness (L) values. Process parameters, WPC and $$ Q_{{{ ext{H}}_{ ext{2}} { ext{O}}}} $$ influence the increase of saturation of C and lightness of L colour value, while H value stays unchanged. Mean value of H was 90.14 ± 1.06, which corresponds to dominance of yellow colour of samples.
Keywords: Extrusion; Corn flour; Whey protein concentrate; Extrudates; Chemical composition; WAI; WSI; Colour

Image Processing Applied to Classification of Avocado Variety Hass (Persea americana Mill.) During the Ripening Process by Israel Arzate-Vázquez; José Jorge Chanona-Pérez; María de Jesús Perea-Flores; Georgina Calderón-Domínguez; Marco A. Moreno-Armendáriz; Hiram Calvo; Salvador Godoy-Calderón; Roberto Quevedo; Gustavo Gutiérrez-López (1307-1313).
This work was undertaken to analyze the ripening process of avocados variety Hass (Persea americana Mill.) by image processing (IP) methodology. A set of avocados (10 samples) was used to follow the changes in image features during ripening by applying a computer vision system, extracting color and textural parameters. Other 16 avocados were used to evaluate the firmness and mass loss. Three maturity stages of avocados were established, and a classification was obtained by applying principal component analysis and k-nearest neighbor algorithm. During the ripening process (12 days), avocado firmness decreased from 75.43 to 2.63 N, while skin color values kept invariable during 6 days; after that, a decrement in the peel green color (a*) was observed (−9.68 to 2.32). Image features showed that during ripening the color parameters (L*, a*, and b*), entropy (4.29 to 4.00), angular second moment (0.287 to 0.360), and fractal dimension (2.58 to 2.44) had a similar path as compared to mass loss, a*, and firmness ripening parameters, respectively. Relationships between image features and ripening parameters were obtained. The parameter a* was the most useful digital feature to establish an acceptable percentage of avocado classification (>80%) in three different maturity stages found. Results obtained by means of IP could be useful to evaluate, at laboratory level, the ripening process of the avocados.
Keywords: Avocado; Ripening; Image processing; Firmness; Fractal dimension

Applying Near-Infrared Spectroscopy and Chemometrics to Determine Total Amino Acids in Herbicide-Stressed Oilseed Rape Leaves by Fei Liu; Zonglai L. Jin; Muhammad Shahbaz Naeem; Tian Tian; Fan Zhang; Yong He; Hui Fang; Qingfu F. Ye; Weijun J. Zhou (1314-1321).
Near-infrared (NIR) spectroscopy was investigated to determine the total amino acids (TAA) in oilseed rape (Brassica napus L.) leaves under a new herbicide—propyl 4-(2-(4,6-dimethoxypyrimidin-2-yloxy)benzylamino)benzoate (ZJ0273)—stress. In full-spectrum partial least squares (PLS) models, direct orthogonal signal correction (DOSC) was the best preprocessing method. Successive projections algorithm (SPA) was used to select the relevant variables. Multiple linear regression (MLR), PLS, and least squares-support vector machine (LS-SVM) were used for calibration. The DOSC–SPA–LS-SVM model achieved the best prediction performance with correlation coefficients r = 0.9968 and root mean squares error of prediction (RMSEP) = 0.2950 comparing all SPA–MLR, SPA–PLS, and SPA–LS-SVM models. Some parsimonious direct functions were also developed based on the DOSC–SPA wavelength (1,340 nm) such as linear, index, logarithmic, binominal, and exponential functions. The best performance was achieved by direct exponential function with r = 0.9968 and RMSEP = 0.2943. The overall results indicated that NIR was able to determine the TAA in herbicide-stressed oilseed rape leaves, and the DOSC–SPA was quite helpful for the development of detection sensors and the monitoring of the growing status and herbicide effect on field crop oilseed rape.
Keywords: Near-infrared spectroscopy; Direct orthogonal signal correction; Successive projections algorithm; Oilseed rape; Amino acids; Least squares-support vector machine

Effect of High Hydrostatic Pressure (HHP) Treatment on Physicochemical Properties of Horse Mackerel (Trachurus trachurus) by Nuray Erkan; Gonca Üretener; Hami Alpas; Arif Selçuk; Özkan Özden; Sencer Buzrul (1322-1329).
The basic objective of this study was to determine the effect of high hydrostatic pressure (HHP; 220, 250 and 330 MPa), holding time (5 and 10 min) and temperature (7, 15 and 25 °C) on some quality parameters of horse mackerel such as colour changes, thiobarbituric acid (TBA-i) and trimethylamine nitrogen (TMA-N), free amino acid content. HHP increased L * values of horse mackerel. The a * and b * of treated horse mackerel did not change significantly after HHP applications. After, HHP, TBA-i and TMA values of all HHP-treated horse mackerel samples remained unchanged than those of untreated samples. The results obtained from this study showed that the quality of high pressure treated horse mackerel is best preserved at 250 MPa, 7–15 °C for 5 min, 220 MPa, 15–25 °C for 5 min, 250 MPa, 15 °C for 10 min and 330 MPa, 25 °C for 10 min.
Keywords: Horse mackerel; High hydrostatic pressure; Colour; Quality