Chapter 3: Double‐Embryo,High‐Protein,High‐Oil Maize Produced Using a Cytokinin‐Based Flower Rescue

ABSTRACT: Maize is an important staple of human diets and animal feed.Improving the nutritional profile for both of these purposes is a desirable research focus and agricultural endpoint. Many mechanisms have been used to improve maize protein and oil content, including selective breeding to introgress desirable traits (Quality Protein Maize), introducing single natural or synthetic genes expressing desired traits, changing signal sequences (high methionine maize), and modifying metabolic pathways (high‐lysine maize, see Chapter 6). A novel approach was used to indirectly increase protein and oil content ( Young and others 2004 ). Maize produces unisexual florets. Within the maize spikelet,the meristem gives rise to an upper and lower floret and male (tassel)‐ and female (ear)‐specific florets are borne on separate inflorescences.The lower floret of each ear spikelet is aborted early in its devel‐opment,leaving the upper floret to mature as the only female floret.Expression of a bacterial cytokinin‐synthesizing isopentenyl transferase (IPT) enzyme,under the control of the Arabidopsis senescence‐inducible promoter SAG 12 (senescence associated gene), blocked the abortion of the lower floret and resulted in 2 functional florets per spikelet.The pistil in each floret was fertile,but the spikelet produced just 1 kernel composed of a fused endosperm with 2 viable embryos.The 2 embryos were genetically distinct, indicating that they had arisen from independent fertilization events. The embryo contains most of the protein and oil in the kernel and kernels that contained 2 embryos have more protein than conventional maize.The presence of 2 embryos in a normal‐sized kernel leads to displacement of endosperm growth, resulting in kernels with an increased ratio of embryo to endosperm content. The end result is maize with more protein and oil and less carbohydrate ( Young and others 2004 ).     

Continuous Versus Discontinuous Ultra‐High‐Pressure Systems for Food Sterilization with Focus on Ultra‐High‐Pressure Homogenization and High‐Pressure Thermal Sterilization: A Review

High‐pressure thermal sterilization (HPTS) and ultra‐high‐pressure homogenization (UHPH) are two emerging sterilization techniques that have not been implemented in the food industry yet. The two technologies apply different acting principles as HPTS uses isostatic pressure in combination with heat whereas UHPH uses dynamic pressure in combination with shear stress, cavitation, impingement, and heat. Both technologies offer significant benefits in terms of spore inactivation in food production with reduced thermal intensity and minimized effects on sensory and nutritional profiles. These benefits have resulted in relevant research efforts on both technologies over the past few decades. This state of the art of the discontinuous HPTS‐based and the continuous UHPH‐based sterilization concepts are assessed within this review. Further, various basic principles and promising future preservation applications of HPTS and UHPH for food processing, that are also applicable in the pharmaceutical, biochemical, and biotechnological sectors, are summarized. In addition, the applications and limitations of these technologies in terms of optimizations needed to overcome the identified challenges are emphasized.     

Laser Scanning System for Real-Time Mapping of Fiber Formations in Meat Analogues

ABSTRACT:  High moisture extrusion has been used to produce vegetable meat analogues that resemble real animal meat and can provide significant health benefits. Since visual and textural properties are key factors for consumer acceptance, assessing fiber formation in the extruded products is important for quality control purpose. Recently, we developed a nondestructive photon migration method to quantify fiber formation in meat analogues. In this study, we implemented this technique in a real-time optical scanning system. This system can scan the entire sample area in real-time and provide 2-dimensional maps to visualize the degree of fiber formation and fiber orientation in the sample. The new system has a potential to provide a fast, nondestructive means for online monitoring of the fiber formation in meat analogues.     

Response of Spores to High‐Pressure Processing

ABSTRACT: This review focuses on the responses of microbial spores to food processes that incorporate high hydrostatic pressures. While the majority of information deals with spores of Bacillus species, spores of Clostridium and Alicyclobacillus species are also discussed, and a section of the review surveys the responses of fungal spores to high‐pressure processing. The mechanisms of the germination of bacterial spores are outlined in detail with regard to spore physiology and structure, along with molecular aspects of germinants and the interaction with spore receptors. Use of treatments combining pressure and temperature for a range of different food products is reviewed, including examples of hurdle technology employing high hydrostatic pressure. Pressure‐assisted thermal sterilization is also discussed.     

Inhibitor‐Assisted High‐Pressure Inactivation of Bacteria in Skim Milk

The combined inactivation effects of high hydrostatic pressure (HHP) and antimicrobial compounds (potassium sorbate and ε‐polylysine [ε‐PL]) on 4 different bacterial strains present in skim milk and the effect of these treatments on milk quality were investigated in this study. HHP treatment at 500 MPa for 5 min reduced the populations of Escherichia coli, Salmonella enterica Typhimurium, Listeria monocytogenes, and Staphylococcus aureus from 6.5 log colony‐forming units (CFUs) or higher to less than 1 log CFU/mL. Compared to HHP alone, HHP with potassium or ε‐PL resulted in significantly higher reductions in the bacterial counts. After 5 min of treatment with HHP (500 MPa) and ε‐PL (2 mg/mL), no growth of E. coli, S. enterica Typhimurium, or L. monocytogenes in skim milk was observed during 15 d of refrigerated storage (4 ± 1 °C). Scanning electron microscopy analysis revealed that the synergistic treatments caused more serious damage to the bacterial cell walls. Quality assessments of the treated samples indicated that the combined treatments did not influence the color, the turbidity, the concentrations of –SH group of the proteins, or the in vitro digestion patterns of the milk. This study demonstrates that HHP with potassium or ε‐PL may be useful in the processing of milk or milk‐containing foods.     

Visual Observation of Hydrolyzed Potato Starch Granules by α‐Amylase with Confocal Laser Scanning Microscopy

Porous starch was produced by digestion of freeze‐dried potato starch with α‐amylase from Bacillus sp. The surface structure of the granules became perforated and in the interior of the granules a capsule‐like cavity was formed, i.e. the hydrolyzed starch can be used as an encapsulant. The structure change of the granules was observed with confocal laser scanning microscopy and scanning electron microscopy. The degree of starch hydrolysis could be correlated with the Avrami equation. The activation energy of starch hydrolysis by α‐amylase was 83 kJ/mol.     

High‐pressure high‐temperature extraction of phenolic compounds from grape skins

This study focused on the use of a non‐conventional extraction technology by employing high‐pressure high‐temperature stirred reactor to extract polyphenols from grape skins. Extraction time (15–330 min) and temperature (30–150 °C) were selected as independent variables, and their effects were studied. A preliminary kinetic study on polyphenols extraction revealed that the second‐order model fitted satisfactorily the experimental results (R² ≥ 0.9798). Total polyphenol yield and total flavonoid (TF) yield, as well as the antiradical power (ARP) of the extracts, were analysed. The use of high‐pressure high‐temperature technology resulted in obtaining extracts rich in polyphenols with high ARP. The highest total polyphenol (60.7 mg_GAE ) and TF (15.1 mg_CE ) yields were obtained at 150 °C for 270 min and 150 °C for 15 min, respectively. HPLC was employed to analyse phenolic compounds. Considerable quantities of single phenolic compounds were extracted. The highest yields of gallic acid, 5‐hydroxymethylfurfural, protocatechuic acid, catechin, vanillic acid, syringic acid, cumaric acid, trans‐resveratrol and quercetin (163.2, 20.0, 69.9, 420.0, 20.6, 603.0, 20.1, 42.4 and 117.1 mg per 100 g_DS, respectively) were found. ARP values were found between 8.45 and 52.17 μg_DPPH .     

High‐resolution 1H NMR investigation of coffee

Recent successful applications of NMR spectroscopy and imaging in food science prompted the authors to use these new techniques for the analysis of espresso coffee. The target of this work was to identify an experimental procedure to obtain maximum information from high‐resolution ¹H spectra. Only the espresso coffee was considered as the true food, since it includes all aromatic substances responsible for the coffee aroma and taste. A big effort was made in order to select an easy, quick and non‐degrading procedure to analyse the espresso cup content, preventing artificial or natural degradation effects with a particular care in the measurement of labile and volatile components. The procedure was tested on two arabica and one robusta samples; each sample was prepared with three roasting degrees to follow the chemical changes due to the roasting process. Moreover, one water extract was prepared also from ground green coffees. As a comparison, each coffee extract was prepared both with a standard ‘espresso coffee machine’ and with a ‘mocha’ as used in the domestic setting. Significant differences among the three samples were observed. Moreover, for all samples, as a function of the roasting degree, a clear trend in the chemical composition was observed. © 1999 Society of Chemical Industry     

High‐performance liquid chromatographic phenolic compound fingerprint for authenticity assessment of honey

BACKGROUND: Phenolic compound profiles of 20 honeys of different botanical origin (eucalyptus, citrus, chestnut and linden) were obtained by high‐performance liquid chromatography with ultraviolet detection after solid phase extraction, in order to evaluate the effectiveness of the fingerprint method for monofloral honey discrimination. RESULTS: A total of 58 peaks were detected at λ = 280 nm. Distinctive phenolic compound profiles were obtained in which both the nature and the relative amount of the detected compounds were characteristic for different botanical source honeys. In order to detect sample groupings, chromatographic peak areas were submitted to principal component analysis. Then linear discriminant analysis was carried out on the first three principal components. In addition, linear discriminant analysis was carried out on the 58 variables, allowing the selection of five variables able to discriminate honeys of different botanical origin. CONCLUSION: The chemometric evaluation of the phenolic compound profiles yielded classification models able to group honey samples according to their floral source with an excellent degree of agreement. The main advantage of the fingerprint approach with respect to traditional methods is that it does not require time‐consuming identification and quantification of the analytes. The method proved to be effective for the assessment of honey authenticity. © 2012 Society of Chemical Industry