Assessing carcass and meat characteristics of Damara, Dorper and Australian Merino lambs under restricted feeding

Seasonal weight loss (SWL) is the most pressing constraint in ruminant production systems in tropical climates. SWL is controlled using supplementation, which is costly and difficult to implement in extensive systems, or using breeds adapted to tropical hot dry climates, like the Damara and Dorper. Albeit 15 years in Australia, little is known on how these sheep compare to Australian Merino. Here, the responses of the Damara, Dorper and Merino breeds to nutritional stress were compared. Seventy-two 6-month-old ram lambs, 24 from each breed, were allocated to growth (gaining 100 g/day) or restricted diets (losing 100 g/day, 85 % of maintenance needs). Animals were weighed and carcass and meat characteristics determined. Results point out to the existence of important differences between the three genotypes, in particular between the Merino and the Southern African breeds. Additionally, Merino ram lambs seem to have been more influenced by SWL than the other two, with consequences on meat characteristics.     

Nutrient management practices among swine operations of various sizes

OBJECTIVE: To determine feeding, cropping, and manure-handling practices of swine operations of various sizes. DESIGN: Producer survey. SAMPLE POPULATION: 85 sow units and 132 finish floors. PROCEDURE: Swine producers were surveyed by mail and during farm visits for information regarding herd characteristics and management practices, with emphasis on the 3 components of the nutrient cycle: cropping, feeding and nutrition, and manure handling. Farms were categorized by operation type as sow units or finish floors and, subsequently, stratified by size as small sow units (< 600 head), large sow units (> or = 600 head), small finish floors (< 2,000 head), and large finish floors (2 > or = 2,000 head). RESULTS: Large sow units and large finish floors were approximately twice as likely to use environmentally sound nutrient management practices as small sow units or small finish floors. These large operations were more likely to use progressive feeding practices, to be aware of their nutrient flows, and to be capable of using these nutrients properly. CONCLUSIONS AND CLINICAL RELEVANCE: There is a need for greater environmental awareness among all swine producers, especially among small producers. This provides a possible growth area for large-animal veterinary consultants. Economy of scale and increased governmental regulations allow large farms to use environmentally sound practices. Thus, large swine farms are not necessarily harmful to the environment.     

美国高平原农业发展对地下水资源的影响及启示

全球范围内的高强度灌溉农业已经造成了严重的地下水危机,威胁农业生态系统和经济社会的可持续运行。在中国北方农耕区,依靠地下水支撑的农业系统正面临严重的水资源问题,其中以华北平原最为严重。美国高平原在近60年中依靠消耗地下水支撑农业生产,小麦、玉米的生产总量分别增加了2倍和10倍,这些农业上的成就却以累积消耗地下水约3 360亿m3为代价,并降低了农业系统应对极端干旱事件的能力。1980年以后,高平原北部地区依靠良好的地下水补给条件并通过地下水的禁采限采、推广喷灌技术等措施降低了地下水的消耗速率。然而由于高平原中、南部地下水采补依然失衡而导致地下水资源持续减少;北部地区在地下水保护的同时却未能有效减少农田的氮肥施用水平,导致地下水浅埋区比较严重的地下水污染。因此,在当下华北平原及我国北方地下水灌溉区大力治理地下水超采问题的实践中,必须与农业面源污染的控制和治理相向而行、质量兼顾、综合统筹。     

Use of a pressuremeter to measure the kinetics of carbon dioxide evolution in chemically leavened wheat flour dough

Among a number of impediments to a wider use of chemical leavening agents in bakery applications is the lack of standardized instrumentation capable of providing information on the rates of CO2 production from chemical leaveners in a format that is meaningful to both the technologist (i.e., the dough rate of reaction or DRR) and the researcher (e.g., in terms of fundamental unitskmol CO2 per kg of dough per s). This paper presents an original methodology to carry out the DRR test using a commercial pressuremeter, the Gassmart apparatus, and to model the kinetics of CO2 evolution of chemically leavened dough. Lean formula doughs were leavened at 27 and 39 degrees C with four chemical leavening systems containing sodium bicarbonate and one of four leavening acids, sodium acid pyrophosphate 40 (SAPP), adipic acid (ADA), potassium acid tartrate (KAT), and glucono-delta-lactone (GDL). Chemical kinetics theory was used to gain an insight into the reaction mechanisms responsible for the evolution of carbon dioxide from the leaveners. A first-order reaction kinetics model was found to be suitable for describing the neutralizing properties of GDL and ADA leavening systems, whereas a first-order reaction kinetics model for irreversible parallel reactions better described the leavening properties of the acidic salts KAT and SAPP.     

Processing conditions influencing the physical properties of French fried potatoes

Summary Achieving optimal colour and texture in French fries requires careful control of the unit operations that convert the raw potatoes into fries. The effects of variation in blanching, drying and finish frying conditions on puncture properties (peak force and peak deformation) and Hunterlab L (lightness) values of French fries were investigated. Fries blanched by low-temperature long-time (LTLT) conditions had larger peak force, peak deformation and L value than fries processed by standard conditions. High-temperature short-time (HTST) blanching increased lightness but decreased peak force and peak deformation. For drying, the colour and textural quality of French fries processed by standard conditions were better than those processed by the drying alternatives. For finish frying, LTLT conditions increased peak force whereas HTST conditions increased lightness. Therefore, a compromise has to be made in processing conditions to optimise both colour and textural quality. Even after finish frying, compositional differences within potato tubers influenced texture, both between and within French fries.     

Modelling Indentation of Bread Crumb by Finite Element Analysis

Finite element analysis (FEA) has the potential for shedding light on the complex mechanical behaviour of many food products. In this paper, the *HYPERFOAM material model in the ABAQUS/Standard FEA package was applied to study the mechanical properties of the crumb of white bread loaves. The applicability of this material model was validated by uniaxial compression stress–strain data. Overall stress–strain curves of low-density bread crumb were well predicted by FEA; altering Poisson's ratio in the simulations (0 and 0·21) made little difference unless the strain was greater than 0·35 for denser crumbs. Experimental compressive Young's modulus and critical stress were well correlated to their counterparts predicted from the FEA material constants in the Ogden strain energy function. The crumb, with characteristics defined by the compressive material constants, was meshed by four-node axisymmetric continuum elements of uniform size to simulate indentation of the crumb. Two cylindrical flat-ended and two spherical indenters were modelled as *RIGID SURFACE. With the axisymmetric indentation FEA model, the load–displacement curves generated from cylindrical indentation were well predicted, whereas those from spherical indenters were under-predicted.     

Effects of Flour Strength,Baking Absorption,and Processing Conditions on the Structure and Mechanical Properties of Bread Crumb

The objective of this study was to determine the effects of flour type, baking absorption, variation in sheeting, and dough proofing time on the density, crumb grain (visual texture), and mechanical properties (physical texture) of bread crumb. All response variables were measured on the same bread crumb specimens. Bread loaves were prepared by a short‐time bread‐making process using four spring wheat flours of varying strength. After crumb density measurement, digital image analysis (DIA) was used to determine crumb grain properties including crumb brightness, cell size, cell wall thickness, and crumb uniformity. Tensile tests were performed on bone‐shaped specimens cut from the same bread slices used for DIA to obtain values for Young's modulus, fracture stress, fracture strain, and fracture energy. Proof time had the most profound influence on the bread with substantial effects on loaf volume, crumb density, crumb brightness, and grain, as well as crumb mechanical properties. Increasing proof time resulted in higher loaf volume, lower crumb density and brightness, coarser crumb with fewer and larger cells with thicker cell walls, and weaker crumb tensile properties. Varying flour type also led to significant differences in most of the measured crumb parameters that appeared to correspond to differences in gluten strength among the flour samples. With increasing flour strength, there was a clear trend to increasing loaf volume, finer and more uniform crumb grain, and stronger and more extensible bread crumb. Increasing baking absorption had virtually no effect on crumb structure but significantly weakened crumb strength and increased fracture strain. In contrast, varying the number of sheeting passes had a minor effect on crumb cellular structure but no effect on mechanical properties. The experimental data were consistent with a cause‐effect relationship between flour strength and the tensile strength of bread crumb arising as a result of stronger flours exhibiting greater resistance to gas cell coalescence, thereby having fewer crumb defects.     

Relationship of Creep-Recovery and Dynamic Oscillatory Measurements to Durum Wheat Physical Dough Properties

Durum wheat gluten strength is important in determining extrusion properties and pasta cooking quality. Durum wheats varying in strength were tested using an alveograph and a 2-g micro-mixograph, both widely accepted techniques for determination of physical dough properties. Doughs from the 2-g micro-mixograph were characterized by dynamic oscillatory and large deformation creep tests using a controlled stress rheometer. Mechanical properties obtained from both testing regimes were strongly correlated with many of the parameters provided by the alveograph and micro-mixograph. Maximum strain attained after 5 min creep ranged from <5% for the strongest least extensible cultivar to >25% for the weakest cultivar, with a coefficient of variation among replicates of <10%. Storage modulus (G′) at 2 Hz ranged from ≈7,000 Pa for the weakest cultivar to >16,000 Pa for the strongest, least extensible cultivars, with a coefficient of variation of <6%. Tan δ (G″/G′) values were ≈0.4 for the strongest versus >0.5 for the weakest cultivars, indicating the larger contribution of the elastic component in the strong cultivars. The rheometer allows discrimination of durum wheat cultivars of varying gluten strength while requiring less sample than traditional physical dough testing techniques.     

Solvent effects on the molecular structures of crude gliadins as revealed by density and ultrasound velocity measurements

Gliadins were extracted from hard red spring wheat flour with 70% (v/v) aqueous ethanol and lyophilized. These crude gliadins were dissolved in 70% (v/v) aqueous ethanol or 4 mM acetic acid with or without ultrasonication. Precise measurements of the density and ultrasound velocity of the solutions were made at 20 °C. For non-sonicated solutions, crude gliadins solubilized in ethanol had a slightly larger partial specific volume (0.76 cm³ g⁻¹), and a larger partial specific adiabatic compressibility coefficient (15 × 10⁻¹¹ Pa⁻¹) compared to those solubilized in acid (0.739 cm³ g⁻¹, 3.1 × 10⁻¹¹ Pa⁻¹, respectively). Larger values are consistent with the existence of complexes formed by gliadins and lipids in aqueous ethanol solutions. Utrasonication had no effect on these protein–lipid complexes based on measurements of density, but it did alter the compressibility of gliadins in dilute acid (making them almost twice as compressible). Novel insights into gluten protein properties can be gained from compressibility measurements of solutions using ultrasonic resonators when coupled with measurements of protein specific volume.