Classification of Brazilian honeys by physical and chemical analytical methods and low field nuclear magnetic resonance (LF H NMR)

This study evaluated the possibility of differentiating the botanical origin of honeys using Low Field Nuclear Magnetic Resonance (LF ¹H NMR). Eighty samples of honey from 8 different botanical sources (eucalyptus, “assa-lipto”, oranges, Barbados cherry, cashew tree, “assa-peixe”, “cipó-uva” and polyfloral) were analyzed. A close correlation (p < 0.01) was established between the LF ¹H NMR analysis and physical and chemical measurements, including water content, water activity, pH and color. Bi-exponential fitting of the transverse relaxation (T₂) data revealed two water populations in all samples, T₂₁ and T₂₂, corresponding to relaxation times of 0.6–1.8 ms and 2.3–5.4 ms respectively. The observed differences in the relaxation times suggest that these were influenced by the differences in botanical origins. Good linear correlations were observed between the T₂ and T₂₁ parameters and the physical and chemical data. This study demonstrated that LF ¹H NMR can be a viable technique for use in classifying honeys by their botanical origin.     

Proton NMR relaxation study of swelling and gelatinisation process in rice starch–water samples

Proton transverse magnetization decay curves of rice flour starch–water samples were measured and analysed for the presence of four components in the relaxation curve. T₂ values were interpreted on the basis of the diffusive and chemical exchange model that provided evidence for extra granular bulk water and three more water populations whose relaxation rate is governed by diffusive and chemical exchange with starch components. The analysis of relaxation data provided information on dynamics of water molecules as well as on the size and dispersion of diffusive domains. Furthermore, by measuring solid to liquid ratio, transverse and longitudinal relaxation curves of starch–water mixtures at increasing temperatures – from 20 to 77 °C – swelling and gelatinisation processes were monitored.     

Investigation of alginate beads for gastro-intestinal functionality,Part 2: In vivo characterisation

This paper summarises work undertaken to visualise and characterise alginate gel beads, in vivo, in the human gastro-intestinal tract using magnetic resonance imaging (MRI). Two types of alginate beads were investigated: “strong” (strongly gelled) and “weak” (weakly gelled) beads, each prepared by long and short exposures to a calcium chloride gelling bath, respectively. Ten volunteers attended the study centre, on two different occasions, and consumed a different bead type on each visit. Before consuming the bead meal, the volunteers consumed 50 ml of Calogen^® (a fatty preload) which converted gastric motility to a fed pattern and delayed the emptying of the non-nutrient model bead meal from the stomach. Gastric emptying of the bead meal was dominated by the fatty preload, with the median half-emptying time 48 min for both bead types. Gastric sieving of the strong beads occurred with the percentage of the meal remaining at 60 min significantly higher for the strong bead meal compared to the weak bead meal. Both types of gelled beads were clearly visualised by MRI in both the stomach and the small intestine, with beads being more visible in the ileum compared to the jejunum and duodenum. The water proton transverse relaxation time, T_2, of the beads was measured in the stomach. After an initial increase, T₂ decreased slightly over time from the initial in vivo measurement. In the first paper of this series, we correlate in vitro T₂ shortening with formation of a more dense gel network. These in vivo investigations suggest that changes in the gel beads, within the GI tract, could be monitored using T₂.     

A study of the retrogradation process in five argentine rice starches

Rate of the retrogradation process of five new argentine genotypes rice starches with different amylose contents and gelatinization temperatures during storage at 4.5 ± 0.5 °C was studied using differential scanning calorimetry (DSC).Significant differences were not found among transition temperatures, i.e., T₀ (onset temperature), T_p (peak temperature) and T_c (conclusion temperature), of non-waxy genotypes when studied using DSC. An increased retrogradation enthalpy (ΔH, mJ/mg) with the storage time occurred with all non-waxy samples. The waxy genotype, W4109, did not show a retrogradation peak for the period under study. Genotypes with high total amylose content (TAM) retrograded more than those with lower content. The kinetic parameters “k” and “n” were evaluated using the Avrami model appearing to be related to the water-soluble amylose (SAM) content. Relationship between the retrogradation degree (%R) and the water-insoluble amylose (IAM) content was found. Gelatinization temperature of the starch (T_G) seemed to affect the retrogradation rate.     

Effects of various sulphuring methods and storage temperatures on the physical and chemical quality of dried apricots

The effects of different sulphuring methods, i.e. sulphuring by “burning the elemental sulphites (BES),” “SO₂ gas from liquified SO₂ tank (SG)” and “dipping into sodium metabisulphite solution (DSM)” on the colour (brown colour formation and carotenoid degradation) and the loss of SO₂ in apricots from Hac?halilo?lu and Kabaa?? varieties stored at 5, 20 and 30 °C for a year were investigated. There were significant effects of variety, sulphuring method and especially storage at 30 °C on the brown colour formation and loss of SO₂ (P < 0.05). As storage temperature–time increased, β-carotene content decreased. Sulphuring methods and variety did not show significant effect on β-carotene content (P > 0.05). The changes in L^∗, b^∗ and C^∗ values were directly associated with β-carotene content and browning values. The most suitable method for all samples, except for Hac?halilo?lu variety stored at 30 °C (BES), is SG, because the samples retained their attractive golden yellow colour during storage.     

Ripening of banana fruit monitored by water relaxation and diffusion 1H-NMR measurements

Water transverse relaxation times T₂ and self-diffusion coefficients D have been measured on banana samples at different ripening stages. Relaxation data have been interpreted on the basis of a chemical and diffusive exchange model proposed by Belton and Hills [Mol. Phys. 61(4) (1987) 999] and Hills et al. [Mol. Phys. 67(4) (1989) 903]. According to that model the observed increase of T₂ values of both cytoplasmatic and vacuolar water may be mainly attributed to the decrease of starch concentration during the ripening process. On the other hand, the observed water self-diffusion coefficient decrease is related to sugar accumulation as starch hydrolysis proceeds. At the early stages of ripening, the individual self-diffusion coefficient values of cytoplasmatic and vacuolar water differ from one another and have been calculated through the analysis of relaxation time-separated pulsed field gradient nuclear magnetic resonance experiments [J. Magn. Reson. A 112 (1995a) 237].     

Short communication: Identification and technological characterization of yeast strains isolated from samples of water buffalo Mozzarella cheese

Sixty yeast cultures were isolated from samples of water buffalo Mozzarella, a popular “pasta filata” cheese, originating on 16 farms located in the provinces of Salerno, Caserta, and Frosinone (Italy). Strains were identified by means of 5.8S internal transcribed spacer rDNA PCR-RFLP combined with 26S rRNA gene partial sequencing and characterized for their ability to exert biochemical properties of technological interest. The recorded dominance of fermenting yeasts such as the lactose-fermenting Kluyveromyces marxianus (38.3% of the total isolates) and the galactose-fermenting Saccharomyces cerevisiae (21.6% of the total isolates) suggests that these yeasts contribute to the organoleptic definition of the water buffalo Mozzarella. The speciographic analysis revealed the presence of 7 other species rarely or never reported in a dairy environment belonging to the genera Pichia and Candida, whose role in Mozzarella cheese organoleptic properties need to be further investigated.     

Investigation of alginate beads for gastro-intestinal functionality,Part 1: In vitro characterisation

This paper summarises the work undertaken to characterise the physico-chemical properties of alginate gel beads in simulated gastro-intestinal (GI) conditions. Two types of alginate beads were investigated: “strong” (strongly gelled) and “weak” (weakly gelled) beads prepared by long and short exposure to a calcium chloride gelling bath, respectively. The beads were found to shrink in gastric conditions and swell in intestinal conditions due to changes in electrostatic forces in the gel matrix at the different pH and ionic strength conditions. We found a good correlation between the NMR transverse relaxation time (T₂) of the water protons within the gel and alginate concentration which was dependant on environmental conditions. T₂ shortening was observed in gastric conditions reflecting the formation of a more dense gel network on shrinking. In intestinal conditions, T₂ increased reflecting the formation of a more open, porous gel network on swelling. This was corroborated by electron microscopy which clearly depicted the changes in gel density in simulated GI conditions. The mechanical properties of the beads similarly reflected the changes in the gel microstructure with the beads becoming stronger in gastric conditions and weaker in intestinal conditions, respectively. The beads were shown to eventually disintegrate towards the end of the intestinal phase which may make these alginate gel beads an attractive option as controlled delivery devices in the gastro-intestinal tract. The in vivo behaviour of the beads within the GI tract is investigated using non-invasive magnetic resonance imaging in the second paper of this series.     

Impact of compression,physical aging,and freezing rate on the crystallization characteristics of an amorphous sugar matrix

Amorphous matrices made up of sugar molecules, are frequently used in food and pharmaceutical industries. A drawback to their use is that they are susceptible to collapse, as a result of water uptake and an increase in temperature and subsequently crystallize. Herein, the crystallization characteristics of amorphous sugar (sucrose and α-lactose) preparations were analyzed, with the purpose of obtaining knowledge that could lead to the prediction of how long the amorphous state is retained under various conditions. The impact of compression, physical aging and freezing rate on the induction period (t_ind) for crystallization were examined. Freeze-dried sugar samples were compressed at 74 or 443 MPa (5 min) and then rehumidified at specified RHs. Some freeze-dried sucrose samples were physically aged, and alternatively freeze-drying was conducted under different conditions. The isothermal crystallization of the prepared samples at different temperatures (T), the glass transition and the crystallization temperature (T_cry) were measured, using differential scanning calorimetry. The compression markedly decreased the t_ind, while significantly lowered the hygroscopicity. Physical aging and slower-freezing also shortened the t_ind. The t_ind was found to be correlated exclusively with (T_cry–T), regardless of rehumidification, compression, sugar type, physical aging and freezing rate in the freeze-drying process.     

Effect of modified atmosphere and vacuum packaging on some quality characteristics and the shelf-life of “morcilla”, a typical cooked blood sausage

The effect of modified atmosphere and vacuum packaging on the shelf-life of “morcilla”, a traditional cooked blood sausage, was investigated. A total of 99 “morcillas” were packaged under vacuum and in modified atmosphere using three different gas mixtures: 15:35:50/O₂:N₂:CO₂ (atmosphere 1), 60:40/N₂:CO₂ (atmosphere 2) and 40:60/N₂:CO₂ (atmosphere 3), and stored during 2, 4, 6 and 8 weeks at 4 °C. Shelf life evaluation was based on pH, water activity (a_w), colour (CIE L*, a*, b*, C* and h*), TBARS formation and microbial counts. The results indicated that, in general, storage time affected (P < 0.05) all parameters whereas no significant differences were observed (P > 0.05) among packaging conditions. Based on the microbial counts, the shelf-life of “morcilla” would be greater than 8 weeks for all packaging conditions. Samples packaged with high CO₂ concentrations (40:60/N₂:CO₂) showed the lowest values of TBARS at the end of storage.     

Effect of protective atmospheres on physicochemical,microbiological and rheological characteristics of sliced Mozzarella cheese

Mozzarella cheese slices packaged in bags of polyvinylidene chloride under vacuum (V) and using a gas mixture of equal parts of CO₂ and N₂ (G) were stored at 4 °C for 8 weeks and analysed at different storage times by physicochemical, microbiological and rheological characterization. Expected values of moisture, total nitrogen, soluble nitrogen at pH 4.6, and chloride contents and of pH were observed. The degradation of α_s1-casein was greater than β-casein degradation, while no significant differences were observed due to the packaging methods. Coliform microorganisms were not detected, while levels of moulds and yeasts counts were acceptable. Expected values of total mesophile counts were obtained. The temperature at crossover moduli (T_c) was determined from temperature sweeps carried out by rheometry. Greater values of T_c were observed in samples G. The influence of temperature on complex viscosity was studied by an Arrhenius-type equation. Activation energy values were obtained from the solid-like region (20–40 °C) and liquid-like region (40–60 °C). A more rapid change in viscosity with temperature was observed when storage time increased and when storage method V was used.     

Physical aging of processed fragmented biopolymers

Low moistures foods containing starches exhibit a sub-T_g endotherm (55–60 °C) when they are stored at constant temperatures. Although the origin of the endotherm is still debatable, it has been attributed to the water–hydroxyl group interactions and/or enthalpic associations between water and carbohydrates. In the present study, physical aging of the starch components of corn flakes prepared with two different levels of starch fragmentation was studied using thermal and rheological methods. A sub-T_g endotherm was observed at temperatures around 50–60 °C by both DSC and Oscillatory Squeezing Flow measurements. An increase of 1.5% of moisture content was observed for both fragmented flakes during aging. The temperatures at which the sub-T_g endotherms occurred were independent of aging and moisture content increase during storage, whilst enthalpy increased with both aging time and moisture content. Although the moisture content of the two types of flakes were different the aging time at which the first endotherm appeared and the rate at which the enthalpy increased were dependent only on the level of starch fragmentation. Corn flakes with a high level of starch fragmentation required a longer period of aging time before the presence of the endotherm could be detected and had a greater rate of increase in enthalpy. Overall, flakes having higher starch fragmentation absorbed more water, and the percent of water uptake decreased with aging time. Flakes with low starch fragmentation exhibited little to no change in water uptake during aging.     

Polycyclic aromatic hydrocarbons (PAHs) in two Spanish traditional smoked sausage varieties: “Androlla” and “Botillo”

The polycyclic aromatic hydrocarbon (PAH) content in two traditional smoked sausages from Spain was determined. Determination and quantification of PAHs in smoked sausages were performed by HPLC with fluorescence detection. Results showed, that total mean levels of PAHs found were higher in “Androlla” (36.45 µg/kg) than in “Botillo” (29.39 µg/kg) although no significant differences (P < 0.05) were observed. In all examined samples content of phenanthrene was the highest in the two traditional sausage varieties. The maximum level for benzo[a]pyrene (BaP) of 5 µg/kg in smoked meat products was not exceeded in any samples. BaP represented 1.3% and 1.2% in “Androlla” and “Botillo” samples, respectively of the total sum of the 15 PAHs investigated in both sausages. Correlation statistic analysis (P < 0.01) showed that BaP was a good marker for 6 IARC possible and probable carcinogenic PAHs in “Androlla” samples (R_BaP/6IARC = 0.63) and in “Botillo” samples (R_BaP/6IARC = 0.96).     

Multivariate classification of rice wines according to ageing time and brand based on amino acid profiles

Discrimination of Chinese rice wines according to ageing time and brand using amino acid profiles was presented in this study. Free amino acids (16) in 98 rice wines were simultaneously determined using high-performance liquid chromatograph-diode array detection (HPLC-DAD). Then the experimental data was subjected to multivariate analysis. Principal component analysis (PCA) was employed to differentiate samples from various ageing times (3, 9, 11 and 15 months) and brands (“pagoda”, “kuaijishan”, and “guyuelongshan”). Partial least square discriminant analysis (PLS-DA) and full (leave-one-out) cross-validation were used to develop classification models. The overall correct classification rate for different ageing times and brands was 99.7% and 94.9%, respectively. The proposed method shows an effective strategy for the detection of mislabelling of rice wines.     

Inhibitory effects of the water extracts of Lavendula sp. on mushroom tyrosinase activity

This study aimed to evaluate the inhibition properties of six lavender species, including Lavendula angustifolia, Lavandula angustifolia “Vera”, Lavendula X allardii, Lavendula stoechas, Lavendula viridis and Lavendula X heterophylla, toward the activity of mushroom tyrosinase. When using l-3,4-dihydroxyphenylalanine (l-Dopa) as the substrate for mushroom tyrosinase, the water extracts of leaves and stems from L. stoechas and L. angustifolia “Vera” showed strong inhibitory effects against the activity of mushroom tyrosinase (70% and 66.4% inhibition, respectively). Oven-drying the leaves and stems or free-drying the water extracts significantly decreased the inhibitory abilities of the water extracts from all lavender species. The water extract from L. stoechas decreased the V_max values when using l-Dopa, catechol and 3,4-dihydroxyphenylacetic acid (DHPAA) as the substrates. It increased the value of K_m when l-Dopa and catechol were the substrates but it decreased the K_m when DHPAA was used. It behaved as a mixed-type inhibitor toward mushroom tyrosinase.     

The effect of salt and fibre direction on water dynamics,distribution and mobility in pork muscle: A low field NMR study

The effect of salt concentration and fibre orientation on water within the meat matrix was investigated by low-field nuclear magnetic resonance (LF-NMR), water-binding capacity (WBC), diffusion studies and histological analysis. Pork M. longissimus thoracis et lumborum samples were cured with 5.7, 15.3 or 26.3% w/w NaCl at a parallel or perpendicular fibre direction. NMR transverse (T₂) relaxation identified three water components (T_2b, T₂₁ and T₂₂) which all exhibited characteristics correlated to WBC. Results indicated that T_2b increases with increasing NaCl concentration. Increasing intra-myofibrillar water and decreasing extra-myofibrillar water resulted in the highest WBC. Water diffused more quickly into the extra-myofibrillar space in samples cured at a parallel fibre direction. This water remained loosely bound in samples cured with the saturated solution (26.3% w/w NaCl) leading to decreased WBC. This study provides further information on water binding within the meat matrix by applying the results of LF-NMR to traditional water-binding theories.     

Isotopic consequences of consumer food choice: Hydrogen and oxygen stable isotope ratios in foods from fast food restaurants versus supermarkets

We investigated geographic trends in the isotopic composition of the modern American diet, purchasing paired food items from fast food restaurants and supermarkets across the USA. We observed large ranges in δ²H and δ¹⁸O values, suggesting variation in the region-of-origin for beef, wheat, and potatoes. Mean restaurant meal δ²H and δ¹⁸O values (−114 and 22.6‰, respectively) were similar to supermarket values (−111 and 22.1‰, respectively). There were no correlations between restaurant beef and local tap water isotope values but significant correlations between supermarket beef and water (δ²H_beef = δ²H_water * 0.19−115‰ and δ¹⁸O_beef = δ¹⁸O_water * 0.17 + 14.8‰) suggesting regionality in the source of beef available to supermarket patrons. We observed no correlations between the stable isotopic composition of carbohydrates and local tap water. Understanding regional differences observed in some foods but not others will help refine parameters in models used to explore human movements in anthropological, archaeological, and forensic studies.     

Determination of royal jelly acids in honey

In the present work we report on the compounds characteristic of larval food (royal jelly, RJ) of the honeybee (Apis mellifera L.) that were identified in 34 different samples of genuine honey and in 3 sugar-adulterated “herbal honeys” by using solid-phase extraction and gas chromatography–mass spectrometry (SPE/GC–MS). The unique feature of RJ is a set of C₈, C₁₀ and C₁₂ hydroxy fatty acids. In all, ten acids characteristic of this bee product were identified in different combinations in the analysed honey samples, namely: 7- and 8-hydroxyoctanoic, 3-hydroxydecanoic, 9-hydroxydecanoic, 9-hydroxy-2-decenoic, 10-hydroxydecanoic, 10-hydroxy-2-decenoic (10-HDA), 3,10-dihydroxydecanoic, 2-octene-1,8-dioic and 2-decene-1,10-dioic acids. The higher relative abundance of these compounds was determined in genuine honeydew and heather honeys, and in “herbal honeys” (23.8–40.8, 18.2–48.5, and 27.0–48.4 μg/g, respectively). Since RJ is known to have strong antibiotic efficacy, our results suggest that a part of the non-peroxide antibacterial activity of honey might be of bee origin.     

STRESS RELAXATION AND LOW FIELD PROTON MAGNETIC RESONANCE STUDIES OF CHEESE ANALOG*

Cheese analog samples were prepared using two different sources of fat milkfat and vegetable oil. The rheological properties of the samples, which ranged in moisture from 42.5 to 50%, were examined using compression and stress relaxation tests. The values of peak stress (s? at 50% strain) from the compression tests and the initial stress (s?_o), equilibrium stress (s?_e), and elastic constant (g₁) from the stress relaxation tests, were compared. All four values were higher for the samples containing milkfat as compared to the samples containing vegetable oil. For both analog formulations, moisture content was negatively correlated with values of s?_o (R² > 0.91), s?_o (R² > 0.80) and g₁ (R² > 0.94) at 40 mm/min crosshead speed. The CPMG‐T₂ relaxation curves of the samples were determined using a low field (5.35 MHz) proton magnetic resonance sensor. The T₂ relaxation data were fit to a two‐term exponential model having time constants T_2a and T_2b In the model, the coefficients α and β indicated, respectively, the contribution of T_2b and T_2b to the T₂ relaxation. The T_2a value was associated with the water in the analog cheese while the T_2b value was associated with the oil. The T_2a value was correlated (R² > 0.95) with the relative proportion of water in each sample. It increased as the moisture content increased. There were negative correlations between T_2a and s?_o, s?_e, and g₁ from the stress relaxation tests.