Interactions of protein content and globulin subunit composition of soybean proteins in relation to tofu gel properties.

The content and globulin subunit composition of soybean proteins are known to affect tofu quality and food-grade soybeans usually have higher levels of proteins. We studied the tofu quality of soybeans with high (44.8%) or low (39.1%) protein content and with or without the 11S globulin polypeptide, 11SA4. Both protein content and 11SA4 significantly affected tofu gel properties. Soybeans containing more protein had smaller seeds which produced significantly firmer (0.663 vs.0.557 N, p<0.001) tofu gels with creamier colour. The absence of 11SA4 was positively correlated with seed size, tofu hardness and water holding capacity and led to significant changes to the profile of storage protein subunits, which may have contributed to the improvement in tofu gel properties. These results suggest that, in combination with higher protein content, certain protein subunits or their polypeptides can also be targeted in selecting soybeans to further improve soy food quality.

Pot size matters revisited: does container size affect the response to elevated CO2 and our ability to detect genotypic variability in this response in wheat?

Many studies have investigated the effect of elevated CO2 (eCO2) in wheat, although few have evaluated the potential of genotypic variability in the response. Such studies are the next logical step in wheat climate change adaptation research, and they will require the evaluation of large numbers of genotypes. For practical reasons the preliminary studies are most likely to be conducted in controlled environments. There have been concerns that the root restriction related to container-grown plants can influence (1) the response to eCO2, (2) the detection of genotypic variability for various traits of interest, and (3) the ability to find the genotypes most responsive to eCO2. In the present study we evaluated two sizes of container - 1.4L pots and 7.5L columns - side-by side in a glasshouse environment and found that for 14 of 23 traits observed environment effects (ambient CO2, eCO2 or eCO2 and high temperature) were not consistent between plants grown in pots and in columns. More importantly, of the 21 traits showing genotypic variability, only 8 showed consistent genotype differences and rankings across both container types. Statistical analyses conducted separately for plants grown in pots or in columns showed different cultivars as being the most responsive to elevated CO2 and would thus, have led to different conclusions. This study is intended as a message of caution to controlled environment experimenters: using small containers can artificially create conditions that could either hide or overly express genotypic variability in some traits in response to eCO2 compared with what might be expected in larger containers.

Effects of soybean protein composition and processing conditions on silken tofu properties.

BACKGROUND: Texture and water holding are important for silken tofu manufacturers and are affected by many factors, including soybean variety and processing conditions. In this study we evaluated these two key quality attributes of silken tofu produced from two soybean varieties - Bunya and Cowrie - using a soak or a dry processing method with glucono-δ-lactone or nigari as coagulant at concentrations of 1.5-5.0 g kg⁻¹. RESULTS: The soak method produced substantially firmer silken tofu with either coagulant. The optimum coagulant concentration to achieve maximum hardness was 2.5-3.0 g kg⁻¹. At 3.0 g kg⁻¹, Bunya produced silken tofu with firmer texture for each of the coagulant-method combinations and lower water loss, an indicator for water holding capacity, for the soak method. The two varieties differed significantly in the composition of major protein subunits for the seed and soymilk. Bunya had no 11SA4, less 11S and more 7S and therefore a lower 11S/7S ratio. CONCLUSION: Both variety and processing conditions affect textural properties and water loss of silken tofu. The absence of 11SA4 and subsequent protein subunit compositions are important in determining these two key quality attributes. Variety Bunya produces silken tofu with firmer texture and lower water loss.

Genotypic variability in the response to elevated CO2 of wheat lines differing in adaptive traits.

Atmospheric CO2 levels have increased from ~280ppm in the pre-industrial era to 391ppm in 2012. High CO2 concentrations stimulate photosynthesis in C3 plants such as wheat, but large variations have been reported in the literature in the response of yield and other traits to elevated CO2 (eCO2). Few studies have investigated genotypic variation within a species to address issues related to breeding for specific adaptation to eCO2. The objective of this study was to determine the response to eCO2 of 20 wheat lines which were chosen for their contrasting expression in tillering propensity, water soluble carbohydrate (WSC) accumulation in the stem, early vigour and transpiration efficiency. Experiments were performed in control environment chambers and in a glasshouse with CO2 levels controlled at either 420ppm (local ambient) or 700ppm (elevated). The results showed no indication of a differential response to eCO2 for any of these lines and adaptive traits were expressed in a consistent manner in ambient and elevated CO2 environments. This implies that for these traits, breeders could expect consistent rankings in the future, assuming these results are validated under field conditions. Additional climate change impacts related to drought and high temperature are also expected to interact with these traits such that genotype rankings may differ from the unstressed condition.