Evaluation of tomato textural mechanical properties

The texture of fresh tomatoes (Lycopersicum esculentum Mill., ‘Momotaro’) at three different stage of ripeness (mature green, pink, and red) was intensively evaluated. The double-cycle load plate compression test showed that initial firmness, average firmness, energy absorption, deformation ratio, and relaxation ratio were sensitive textural parameters for identifying the maturity stages. From a puncture test, initial firmness, average firmness, apparent modulus of elasticity, rupture force, toughness, and deformation at the rupture point were sensitive to the maturity stages. The mature unripe tomato deformed linearly as a function of force; hence, the firmness was constant. However, the fully ripe tomato firmness increased as a function of applied force. The fruit strain increased during ripening, and it was independent of fruit size. The unripe tomato was more elastic than the ripe one. The peel at the mature green stage contributed approximately 70% of the firmness of the fruit and approximately 90% at the pink stage and red stage. The rupture force by the puncture test (traditionally, peak force) was correlated well with other textural parameters, which indicated that it could be used as a firmness representative parameter, as has been used by many researchers. The degree of elasticity was a better indicator for elasticity than the relaxation ratio.     

Freezing protocol effect on quality properties of fruit tissue according to the fruit, the variety and the stage of maturity

Among the changes induced by freezing of fruits, it is still difficult to determine the major properties which are the most representative of quality variation. A range of characteristics (texture, color, soluble solids, water activity, water content, pH, titrable acidity) were determined before and after three different freezing protocols (at −20 °C in a cold chamber, at −80 °C in gas nitrogen convection chamber and after immersion in liquid nitrogen at −196 °C) for two fruit types (apple-Malus domestica Borkh- and mango - Mangifera indica L. cv. ‘KENT’-), two varieties of apples (Golden Delicious and Granny Smith) and two maturities of one variety (ripe and unripe Granny Smith). Freezing induced significant changes mostly in texture, color and soluble solids. Property variations due to freezing depended mainly on the type of fruit, to a lesser extent on the variety of apples studied and slightly on the maturity of Granny Smith apples. Among the freezing conditions tested, gas nitrogen convection at −80 °C appeared to be the best choice for limiting fruit quality degradation.     

Effect of beeswax content on hydroxypropyl methylcellulose-based edible film properties and postharvest quality of coated plums (Cv. Angeleno)

The effect of beeswax (BW) content of hydroxypropyl methylcellulose (HPMC)–BW edible coatings on stand-alone film properties and on postharvest quality of coated ‘Angeleno’ plums was studied. The coatings contained BW at 4 lipid content levels (0, 20, 40 and 60 g/100 g, dry basis). Coated and uncoated plums were stored 4 weeks at 1 °C and transferred to 20 °C for 1–3 weeks. Addition of BW to the HPMC film matrix reduced film mechanical resistance and oxygen barrier, and improved film moisture barrier. Film mechanical properties showed a good fit with an exponential and/or linear model that could provide a useful tool to predict mechanical properties with others HPMC–BW composition mixtures. Coatings with BW reduced plum weight loss compared to HPMC-based coatings with no BW. Plum weight loss decreased as BW content increased from 20 to 40 g/100 g, but above 40 g/100 g BW content, weight loss was not further reduced. Whereas, water vapor permeability of stand-alone films decreased significantly as BW content increased to 60 g/100 g. Coatings reduced plum softening and bleeding, with those with lower BW content being more effective, which could be related to the ability of coatings to create a modified atmosphere in the fruit. Flavor was not affected by coating application. Results indicate that HPMC–BW coatings with 20 g/100 g BW would provide the best compromise to extend shelf life of ‘Angeleno’ plums.     

Potential use of physical measurements including ultrasound for a better mango fruit quality characterization

The potential use of ultrasound measurements, combined with other physical measurements, has been investigated. The good relationship between soluble solids content (SSC) and ultrasonic wave velocity reported in the literature being confirmed by our study, our main goal was to evaluate the added value of ultrasound measurements around 25 MHz for the determination of biochemical compounds responsible of organoleptic quality of mangoes. Among the main sugar constituents of mango juice, only sucrose content prediction was improved by combining SSC and ultrasonic waves velocity using a PLS model (R² = 0.81, RMSECV = 12.3, bias = 0.10, RPD = 2.3) when compared to the linear model with SSC only (R² = 0.75, SEP = 14.05, bias = 0.08). The same conclusion was obtained for titratable acidity PLS model using whole fruit hardness, SSC and ultrasonic wave velocity (R² = 0.82, RMSECV = 1.84, bias = 0.02, RPD = 2.4) compared to the linear model with fruit hardness only (R² = 0.78, SEP = 2.07, bias = 0.02). However, the added value of ultrasound measurements was not always found to be significant (P = 0.05) when a Wilcoxon statistical tests was conducted on the residuals of the linear and PLS models for both sucrose and titratable acidity.     

Effect of Cultivar and Ripening Stage on Quality and Microstructure of Frozen Mangoes (Mangifera indica Linn.)

The aim of this work was to investigate the quality and microstructure of different frozen mango cultivars. Since freezing can cause severe textural damage to fruit, the proper selection of a ripening stage and cultivar can reduce such damage. Two mango cultivars (Nam Dok Mai and Chok Anan) were allowed to ripen for four ripening stages. During ripening, titratable acidity, alcohol-insoluble residues, and firmness significantly decreased while total soluble solids, total pectin, and water-soluble pectin levels increased. Mangoes from the three final ripening stages were frozen until the temperature of the samples reached –25°C. After thawing, the partially ripe mango samples exhibited the highest firmness, lowest drip loss, lowest water-soluble pectin, and the highest sensory firmness scores. The microstructure found using light microscopy and transmission electron microscopy showed that all frozen-thawed mangoes exhibited a swelling and folding of the cell wall due to freezing damage. The cell walls of fully ripe mangoes were dramatically damaged, which explained the low firmness values. Tissue and cell wall damage in Nam Dok Mai were the greatest, which contributed to the large drip loss. The cheaper Chok Anan cultivar was more resistant to freezing damage than Nam Dok Mai.     

Antiplasticization effect of water in amorphous foods. A review

Water is the most effective plasticizer in food matrices, decreasing glass transition temperature (T_g) and mechanical resistance and determining a softening effect with the increasing of its concentration. However an opposite effect (i.e. hardening, toughening) could be observed in some food and in specific moisture or a_w range and this is referred to an anti-plasticization effect. Several are the possible causes for this phenomenon and various are the factors that have been recognized to affect its occurrence in a food matrix: mechanical testing method, mechanical parameter tested, type of food (composition and micro-macrostructure).     

Rheological,textural, micro-structural and sensory properties of mango jam

Mango jam behaved as pseudoplastic fluid exhibiting yield stress. The Herschel–Bulkley (HB) model described adequately the steady-state rheological behavior of jam. Temperature dependence of the consistency index followed Arrhenius relationship. Time dependent structural breakdown characteristics of mango jam followed Hahn model. Hardness of mango jam increased with pectin concentration and acidity. Hardness increased up to 60% sugar concentration but decreased with further increase in sugar concentration at all pH and pectin levels. Stickiness, work of shear, and adhesion did not show any systematic trend with pH, pectin, and sugar concentration. The overall acceptability was rated highest for mango jam prepared with 65% sugar, 1% pectin at pH 3.4. Principal component analysis (PCA) revealed that hardness and work of shear are the most relevant among all the characteristics (physicochemical, sensory, textural, rheological, and compositional) studied for mango jam. Microstructure of mango jam was found to be composed of network regions with large pores as well as dense, compact regions with small pores.     

Limiting the deterioration of mango fruit during storage at room temperature by oxalate treatment

Effects of oxalate on the incidence of decay and ripening in mango fruit, and its physiological effects on the peel and flesh of mango were investigated after mango fruit (Mangifera indica L.) were dipped in different oxalate solutions for 10 min and then stored at 25 °C. Oxalate application decreased the incidence of decay and delayed the ripening process in mango fruit during storage. Potassium oxalate treatment resulted in increased activities of peroxidase (POD) in both the peel and the flesh and polyphenol oxidase (PPO) in the peel, without activation of phenylalanine ammonia-lyase activity, and elevated total phenolic content in the peel. The physiological effects of oxalate in increasing activities of POD and PPO and elevating total phenolic level could be involved in induced resistance of mango fruit against postharvest disease. Oxalate application could be a promising method to suppress postharvest deterioration and extend the useful shelf-life of mangoes.     

从力学性质测试与感官鉴定分析加热方式对马铃薯组织结构的影响

马铃薯片分别以沸水、蒸汽和微波三种方式加热一段时间后,测其中心温度,并经力学性质测试和感官鉴定两种方法对其组织结构变化进行评价。实验发现不论哪种加热方式,两种评价结果都存在着相互对应的关系;薯片组织结构变化的程度,并不完全取决于加热后食品中心达到的温度,而主要与加热方式和加热速率有关。     

小麦淀粉凝胶质构特性研究

为了掌握不同小麦品种淀粉凝胶质构特性;陕西关中小麦品种和西澳面条用小麦品种的淀粉凝胶质构的异同;淀粉的直链淀粉含量、色度及粘度特性与淀粉凝胶质构特性的关系。以参加陕西省关中小麦品种区域试验的15个小麦品种(品系)、西澳8个面条用小麦品种(品系)为材料,研究了小麦品种淀粉凝胶质构特性及淀粉特性与凝胶质构特性的关系。结果表明:不同小麦品种淀粉凝胶质构特性不同,陕西关中小麦品种之间淀粉凝胶质构特性比西澳面条小麦品种之间差异大。直链淀粉含量与凝胶特性无明显关系;色度中L值与凝胶硬度呈显著正相关;粘度特性与淀粉凝胶质构特性显著相关。关中小麦品种小偃6号、小偃128、秦农068和西澳面条小麦品种具有相似的凝胶质构特性。     

Antifungal activity of five different essential oils in vapour phase for the control of Colletotrichum gloeosporioides and Lasiodiplodia theobromae in vitro and on mango

Mango fruit has high commercial value; however, major postharvest losses are encountered throughout the supply chain due to postharvest diseases. These results lead to the search for natural fungicide for postharvest diseases control. The antifungal effects of five essential oils (thyme, clove, cinnamon, anise and vitex) were assessed by disc volatilisation method. Thyme oil vapours at 5 μL per Petriplate, and clove and cinnamon oil at 8 μL per Petriplate showed 100% growth inhibition of mango pathogens in vitro. GC/MS analysis of essential oil showed thymol (23.88), o‐cymol (23.88) and terpinolene (23.88) as the major constituents of thyme oil. Clove and cinnamon oils contain 3‐allyl‐2‐methoxyphenol (37.42%) and benzofuran 3‐methyl (17.97%), respectively. Thyme oil as a fumigant at 66.7 μL L^?1 showed a significant (P < 0.05) inhibition on postharvest pathogens of mango fruits stored at 25 °C for 6 days. Results of our study suggest the possibility of using thyme oil as an alternate natural fungicide to manage postharvest diseases in mango.     

Physico-chemical and antioxidant properties of four mango (Mangifera indica L.) cultivars in China

Four principal mango cultivars (Tainong No.1, Irwin, JinHwang and Keitt) grown in southern China were selected, and their physico-chemical and antioxidant properties were characterized and compared. Of all the four cultivars, Tainong No.1 had highest content of total phenols, ρ-coumaric acid, sinapic acid, quercetin, titratable acidity, citric acid, malic acid, fructose, higher antioxidant activities (DPPH, FRAP) and L^∗, lower pH, PPO activity and individual weight. Keitt mangoes showed significantly (p < 0.05) higher contents of β-carotene, ρ-hydroxybenzoic acid, sucrose, total sugar, total soluble solid, catechin, succinic acid and higher PPO activity. JinHwang mangoes exhibited significantly (p < 0.05) higher individual weight and PPO activity, but had lower content of total phenols, β-carotene and lower antioxidant activity. Principal component analysis (PCA) allowed the four mango cultivars to be differentiated clearly based on all these physico-chemical and antioxidant properties determined in the study.     

Textural properties of mango soy fortified probiotic yoghurt: optimisation of inoculum level of yoghurt and probiotic culture

The effect of yoghurt bacteria and probiotic culture on the textural characteristics of mango soy fortified probiotic yoghurt (MSFPY) is studied. The TA-XT2 Texture Analyser was used to measure the textural characteristics of MSFPY prepared from blends containing varying proportions of yoghurt bacteria [ Streptococcus thermophilus (ST), Lactobacillus bulgaricus (LB)] and probiotic culture [ Bifidobacterium bifidus (BB), Lactobacillus acidophilus (LA)]. MSFPY samples were prepared by using blends of 78.3% toned milk, 14.5% soy milk and 7.2% mango pulp. Texture profile data were used to develop regression models for dependent variables – hardness, cohesiveness, adhesiveness, springiness and gumminess. The optimisation of culture addition was done by comparing the yoghurt with the MSFY as control sample (ST and LB at 2%, 1:1) The mean optimum culture addition rate of –1.43 (0.79%) ST, –1.51 (0.75%) LB, –1.43 (0.79%) BB and –1.10 (0.95%) LA is recommended for yielding an acceptable and good quality of MSFPY.     

A new region-primitive method for classification of colour meat image texture based on size, orientation, and contrast

A new structural method was developed to characterise texture of colour meat images. Structural primitives or region-primitives were constructed using a region-growing method with a global and automatically calculated threshold. A total of eight textural features under the consideration of size, orientation, and contrast, which are the primary factors of human perception of texture pattern, were obtained from the region-primitives. An experiment was set up to classify the texture pattern of a set of 60 cooked meat colour images consisting of 20 beef images, 20 lamb images, and 20 pork images using texture features obtained from the proposed region-primitive method and run-length matrix method, respectively. The proposed region-primitive method (error rate: 18.3%) was found to perform better than the run-length matrix method (error rate: 35.0%). Results also indicated that the texture features obtained by the proposed method carried adequate texture information for classification and that the proposed region-primitive method could be potentially used for the characterisation of irregular textural pattern in cooked meat images, which was inapproachable by conventional structural texture analysis techniques.     

阳离子种类和添加量对鲢鱼糜 凝胶力学特性的影响

目的 比较一价金属离子和二价金属离子对鲢鱼糜凝胶力学性能的影响。方法 向加入2.5%NaCl的鱼糜中添加不同浓度的KCl 、CaCl2、MgCl2(0、10、20、30、40、50mmol/kg)、ZnCl2(0,0.02,0.04,0.06,0.08,0.10mmol/kg),研究金属离子对鱼糜凝胶穿刺和TPA性能的影响,并通过蠕变参数的变化研究阳离子与大分子的相互作用。结果 一价阳离子K 对鱼糜凝胶品质影响较小,二价阳离子(Mg2 、Ca2 、Zn2 )能够显著提高鱼糜的硬度、弹性、松弛时间和黏流指数。MgCl2、CaCl2 和ZnCl2 的最适浓度分别为40-50mmol/kg、20-30mmol/kg和0.06-0.08mmol/kg。结论 二价金属离子(Mg2 、Ca2 、Zn2 )能够促进蛋白质伸展,并与蛋白质侧链-COOH形成“盐桥”, 同时Ca2 还能激活内源性转谷氨酰胺酶(TGase)活性,促进ε-(γ-Glu) – Lys的形成,提高鱼糜凝胶力学性能,而一价金属K 会显著提高鱼糜凝胶的持水性。