RHEOLOGICAL INDICES OF FRUIT CONTENT IN JAMS: INFLUENCE OF FORMULATION ON TIME-DEPENDENT FLOW OF SHEARED STRAWBERRY AND PEACH JAMS

The influence of formulation factors [fruit content (25–55%), soluble solids content (60–70° Brix) and added pectin (0.3–0.7% in strawberry jams and 0.1–0.5% in peach jams)] on time dependent parameters has been analyzed in previously sheared jams. Twenty three samples of each fruit jam were prepared according to a second order composite rotatable design. Weltmann A values depended mainly on fruit content and on its interaction with the other two composition factors for both fruit jams. Weltmann B values, depended on the three variables and on fruit-pectin interaction for strawberry jams, while for peach jams B values depended also on fruit-soluble solids interaction.
Predictive power of time dependent parameters for estimation of fruit content was low, but considering them in conjunction with soluble solids content and total pectin values explained 91.7% of the variability of fruit content in strawberry jams and 83.7% of same in peach jams.     

RHEOLOGICAL BEHAVIOUR OF SHEARED JAMS. RELATION WITH FRUIT CONTENT

Eight samples of jam were sheared to destroy gel structure and their flow behaviour was analysed in a concentric cylinder viscometer. Jams were prepared from 4 different fruits—strawberry, peach, plum, and apricot—at 50% and 30% fruit content approximately. Flow of sheared jam showed time dependence, which could be quantified by the Weltmann model and which was eliminated by shearing samples for 8 min at 300 rpm. Casson's yield stress values were obtained at two ranges of shear rates: 0.08–1.01 s⁻¹ (O₀₁) and 2.58–387.30 s⁻¹ (o₀₂). o₀₂ values were about double the o₀₁ values. Flow was adequately described by the Herschel and Bulkley model, introducing either of the yield stress values (o₀₁ or o₀₂). Significant differences were found for some of the rheological parameters studied (Weltmann A and B constants, o₀₁, o₀₂, K₁, and n₁) between samples containing 50% and 30% fruit. These results demonstrate the role played by fruit particles in the rheological behaviour of this type of product and suggest the possibility of using rheological parameters as indices of fruit content in jams.     

EFFECT OF UNIMODAL PARTICLE SIZE AND PULP CONTENT ON RHEOLOGICAL PROPERTIES OF TOMATO PUREE

The vane method in controlled shear stress mode was used to determine the yield stress and the shear rate—shear stress data of tomato purees containing 10–35% pulp of two different average particle sizes: 0.34 and 0.71 mm. Consistency index and apparent viscosity increased significantly with pulp content and decreased with average particle size. The effect of pulp weight fraction (P) on relative viscosity (η_r) could be described by the single parameter equation: η_r= [1 – (P/A)]⁻², while the effect of particle diameter on η_r could be described using Peclet number. Magnitudes of yield stress determined directly by the vane method were higher than those obtained by using the Casson model, and were proportional to the square of pulp content. Reduced Casson yield stress—P data on purees of both particle sizes followd a single curve. Effects of pulp content and particle size on vane yield stress and apparent viscosity were evident from the correlation forms with high values of R².     

1-甲基环丙烯对桃果实成熟软化调控的影响

以“雨花三号”桃果实为试材，研究了1-甲基环丙烯（1-MCP）处理后对桃果实乙烯生物合成途径和细胞壁降解相美酶的影响。结果表明：1-MCP处理能够延缓果实后熟软化进程，降低了桃果实乙烯释放量，并抑制了果实快速软化阶段的ACC氧化酶（ACO）的活性；对多聚半乳糖醛酸酶（PG）和α-L-阿拉伯呋喃糖苷酶（α-AF）活性均表现一定的抑制作用。     

EFFECT OF PECTIN CONTENT ON FLOW PROPERTIES OF MANGO PULP CONCENTRATES

The effect of pectin on the flow properties of mango pulp concentrates was studied using a coaxial cylindrical viscometer in the temperature (T) range 303-343°K. The variables were soluble solid content(C) 16-30°Brix, pectin content (C_pec, range 0.0323-0.0349 dry wt fraction) for the shear rate (γ) range 9.0-250 s^-1. Mango pulp concentrates behaved as pseudoplastic fluids in the entire pectin content range with a flow behaviour index of 0.286. A model relating shear stress () with the above variables is presented:     

INFLUENCE OF YEAR,CULTIVAR AND FRUIT MATURITY ON QUALITY OF PEACH PUREE1

A 3-year study was conducted to evaluate the effect of year, cultivar and fruit maturity on the quality of peach puree and to determine the relative importance (RI) of these factors on the quality components hue angle (color), pH, acidity, soluble solids (SS) and SS/acid ratio. The results indicated that year, cultivar and fruit maturity had a strong effect and that they are very important in determining the quality of peach puree by affecting the different quality components. In general, fruit maturity had stronger RI than year and cultivar on the quality parameters studied. The data obtained for different maturities and cultivars fit a linear regression that accounted for 95% of the variability for all quality parameters measured. pH and SS/acid ratio increased while acidity and hue angle decreased and SS showed small or no increase as the fruit reached more advance stages of maturity.     

FACTORS INFLUENCING THE BREAKDOWN OF FRUIT IN STRAWBERRY JAM

Abstract. Structural changes produced in strawberries when made into jam were studied by light microscopy. The results indicated that only the epidermal and vascular tissues retained their structural integrity, whereas the bulk of the cells were collapsed and in some instances ruptured. The extent to which fruit of different cultivars broke down during the jam making process was determined, and an expression representing fruit wholeness was derived. It is concluded that a relationship exists between the extent to which strawberries disintegrate during jam boiling and the density of achenes on the surface of berries of a given size.     

EFFECT OF TEMPERATURE ON VISCOSITY OF FRUIT JUICES AND PUREES

SUMMARY: The viscosities of selected fruit juices and purees were measured with a coaxial-cylinder viscometer in the temperature range 20–70°C. Depectinized apple juice and Concord grape juice were Newtonian fluids at all concentrations and their viscosity decreased considerably at higher temperatures. Cloudy apple and orange juices changed from Newtonian to pseudoplastic at concentrations higher than 50 and 20° Brix. respectively. Temperature had a smaller effect on viscosity of cloudy juices than of clear juices. The apparent viscosity of fruit purees (pseudoplastic fluids) decreased slightly at higher temperatures. The activation energy for flow increased with the juice concentration and decreased with the presence of suspended particles in the fruit product. The data and conclusions are useful in the design and operation of efficient food-processing equipment.     

臭氧处理对厚皮甜瓜采后生理及贮藏品质的影响

在6℃贮藏条件下,分别对86-1厚皮甜瓜采用浓度为2.5、1.5、0.6μL/L臭氧间隙处理(每48 h处理1次),结果表明,2.5μ/L臭氧间隙处理能显著抑制厚皮甜瓜86-1的呼吸与乙烯的生成,延缓果实的衰老,并显著地抑制可滴定酸和还原糖含量的下降,能明显地延长厚皮甜瓜86-1的贮藏期并维持甜瓜品质.而臭氧处理浓度越低,贮藏效果越差,贮藏期越短.     

EFFECT OF ACETIC ACID AND CMC ON RHEOLOGICAL AND BAKING PROPERTIES OF FLOUR

The effects of addition of acetic acid (0.05, 0.1, 0.2 and 0.4%) and carboxymethyl cellulose (0.25, 0.5, 1.0, 2.0%) on rheological, gas release and bread making properties of flour were examined. Water absorption, dough stability, dough development time, loaf volume and overall acceptability scores decreased, while degree of softening and bread firmness increased with an increase in acetic acid concentration. Addition of CMC showed similar effects on dough stability, dough development time and degree of softening. Maximum dough height (H_m), maximum height of CO₂ production (H,_m), gas formation and retention decreased with the increase in acetic acid and CMC levels. Addition of 0.05% of acetic acid in combination with 0.25% CMC was most effective in improving dough characteristics, and overall acceptability scores.     

发酵方式及起始pH值对泡菜亚硝酸盐及硝酸盐含量的影响

以甘蓝为主要原料,采用自然发酵、陈泡菜卤水发酵、乳酸菌接种发酵以及调整起始腌渍液的pH值等发酵工艺,对泡菜腌渍过程中pH值变化、硝酸盐及亚硝酸盐的消长变化规律及影响因素进行了研究和分析.     

THE EFFECT OF PHYTATE AND FIBER CONTENT ON COOKING QUALITY IN FABA BEANS

Seventy-six faba bean lines were analyzed for their phytic acid content in the whole seeds and in the cotyledons. The fiber content was also determined in 17 Faba bean lines. The seed weights; % testa weight-of the seeds; and % moisture uptake (water imbibition) after overnight soaking in distilled water or increasing concentrations of EDTA solutions were measured and recorded. The relation between the above mentioned dependent variables and the cooking time for seed softening (min.) in 76 faba bean lines was studied and simple and multiple correlation coefficients were computed with a total of 70 operations. Significant correlation coefficients were found between phytic acid content in the cotyledons, % testae weight of the seeds; moisture uptake after soaking the seeds in distilled water overnight and cooking time for 50% softening (min). The faba bean lines 606/ 303; 606/ 308, 608/ 334, 609/ 350, proved to be of excellent cooking quality, since their cooking time for 50% seed softening did not exceed 10 min.     

EFFECT OF PROCESSING CONDITIONS ON THE COMPOSITION AND RHEOLOGICAL PROPERTIES OF APPLESAUCE

The relation between the composition and rheological properties of applesauce was studied in two ways. For artificial applesauces, reconstituted from isolated applesauce particles and applesauce serum, the residual shear stress increases exponentially with pulp content. Below a particle size of 0.625 mm the values of residual shear stress and apparent viscosity are lower for smaller particles. The effect of the processing conditions (finisher screen openings and cooking time) and raw material (apple variety and ripeness) on particle size and pulp content was studied on sauce made in a pilot plant. The particle size and pulp content of these applesauces affect the rheological properties in the same way as was shown for the artificial applesauces.     

乙醇处理对桃果实贮藏期间POD、PPO活性的影响

以“大久保”和“绿化9”桃果实为试材,研究了在10℃±2℃和2℃±2℃贮藏条件下,不同浓度的乙醇蒸汽处理(1mL/kg、2mL/kg、4mL/kg)对桃果实POD、PPO活性的影响。结果表明“,大久保”用4mL/kg浓度的乙醇在10℃±2℃下处理3d,“绿化9”用4mL/kg浓度的乙醇在2℃±2℃下处理5d,有效提高了桃果实POD的活性,加强了机体的抗氧化系统,保持膜的完整性,减少冷害发生,同时抑制了果实PPO活性,减少果实褐变和腐烂病的发生,延长了贮藏期。