Ice cream mix was fermented with yogurt cultures of Streptococcus thermophilus and Lactobacillus bulgaricus to four different pH's then frozen in a batch ice cream freezer. A consumer panel of 120 people tasted samples of strawberry flavored product with pH's of 4.4, 4.7, 5.1, and 5.4 and commercial frozen yogurt as a standard. Results from the panel were used to predict a preferred pH of 4.9. Another panel of 181 people compared product at pH 4.9 with 10, 15 and 20% strawberry flavoring. There was not a statistically significant difference among levels of flavoring. Starter culture populations and lactase activity were monitored for one month both in yogurt and in the frozen fermented ice cream mix. Lactase activity and colony counts progressively decreased in refrigerated yogurt at 4°C during the 30-day period. In frozen fermented ice cream mix, lactase activity and colony counts decreased slightly. The fermented ice cream mix can be held frozen for more than one month with active lactase activity, and viable colony counts, but refrigerated yogurt does not have a shelf life of more than one month.

Thesis (doctoral)--Helsinki University of Technology, 2007. / Includes bibliographical references. Also available on the World Wide Web.

A novel technology to process traditional chocolate-making ingredients has been investigated with the main objective to promote the generation of key chocolate odorant volatiles as a part of the commercial interest of the industrial partner to create a new line of natural products with intense chocolate flavour. The novel technology is based on the thermal generation of flavours (non-enzymatic browning) using a closed-batch reactor that is able to hold six bars of overpressures, speeding up the aromatic reactions, and the use of enzymes to increase the flavours precursors. Pilot scale experiments were carried using sugars, cocoa powder and water in various ratios and were submitted to temperatures from 70°C to 130°C during various reaction times (1 to 10 hours) reaching over pressures from 0.2 to 3.5 bars. The assessment of the evolution of the products obtained was carried out chemically and sensorially. Chemically, using a laboratory-developed headspace solid phase microextration gas chromatography mass spectrometry (HS-SPME-GC-MS) methodology and sensorially with a trained panel of tasters. Temperatures of 130°C with enzymatic pre-treatment of the cocoa resulted with the highest generation of volatiles scoring the maximum in the aromatically but on the other hand 90°C, without enzymatic pre-treatment, had the best taste evaluation.

Rice bran, a by-product from rice milling, is an excellent source of natural antioxidants. Lipids in rice bran appear as small spherical droplets called oil bodies. This work attempted to recover the oil bodies from rice bran (fresh, stored and heat-treated) and to determine their chemical, biochemical and physical properties ex vivo. As revealed by transmission electron microscopy, oil bodies were observed mainly in the sub-aleurone and aleurone layer of brown rice. Oil bodies were successfully recovered from rice bran and were enriched in tocochromanols and oryzanol (656 - 1,006 mg/kg lipid and 8,880 - 9,692 mg/kg lipid respectively). Further washing to remove extraneous protein and non-associated compounds, effective lipid concentration increased while protein concentration decreased. The washed oil body preparation contained approximately 35 - 68 % tocochromanols and 60 - 62 % oryzanol of the parent rice bran oil. Therefore, the majority of tocochromanols and oryzanol molecules appeared to be intrinsically associated with rice bran oil bodies ex vivo. Fatty acid composition of rice bran oil bodies was similar to that of parent rice bran. SDS-PAGE of proteins present in differentially washed oil body preparations revealed similar protein profiles; however, there was a relative enrichment of the bands at 16 - 18 kDa (typical molecular weight of oleosins). Rice bran oil bodies possessed negatively charged surface (-30 mV) at neutral pH. As the pH of the oil body suspension was lowered to the pH near pI (about pH 4 - 5), zeta potential of the oil bodies approached zero and the suspension had the least physical stability; aggregation and the least relative turbidity. The biochemical instability of rice occurs immediately after milling, which leads to the limited use of rice bran for human consumption. Free fatty acids and lipid hydroperoxides in rice bran and corresponding oil bodies increased significantly (P<0.05) during storage. Oil bodies recovered from stored rice bran aggregated and coalesced. 41% of tocochromanols in the oil bodies had decomposed while the concentration of oryzanol was relatively stable during the storage. Rice bran heat treatments (pan roasting and extrusion) caused the coalescence of oil bodies in vivo and the instability of an oil body suspension ex vivo. The main findings of this study were that rice bran oil bodies were enriched in phytochemicals including tocochromanols and oryzanol and were resistant to oxidation providing that the oil bodies were still intact. The oil bodies could delay the onset of lipid oxidation of stored lipids inside the oil bodies. This may be explained by the physical barrier of surface membrane protein (oleosin) against pro-oxidants and the intrinsic association between the oil bodies and phytochemicals in rice bran.

Thesis (M.S.)--Wisconsin. / Includes bibliographical references (leaves 84-85).

Dark chocolate as the main subject matter in this study was investigated for physical changes when formulated with two different lipids based ingredients impacting on the chocolate flow properties. The first ingredient was limonene, known to reduce viscosity when substituting a small fraction of the cocoa butter and to affect cocoa butter crystal morphology, but without knowledge of the impact on bloom formation. The second lipid ingredient was a polar lipid extract from green leaf tissue hypothesised to show functionality as a flow aid, potentially enabling the replacement of currently applied commercial surfactants in chocolate. The driver for this part of the PhD study was to uncover alternatives for the commercial surfactant polyglycerol polyricinoleate (PGPR) which has a negative consumer image. This study was also carried out to devise an opportunity for functionalisation of green tissue waste, although in this first investigation, fresh spinach was used as the raw tissue material. As DGDG was claimed to be the polar lipid compound that caused the low viscosity reduction of dark chocolate by oat lipids, DGDG as well as MGDG are also available abundantly in spinach. The limonene work was using the techniques of whiteness index (WI) to detect bloom, X-ray diffraction (XRD) for crystal identification and differential scanning calorimetry (DSC) for the melting behaviour. Limonene significantly influenced the cocoa butter crystal transformation rate in chocolate which further promoted the development of clearly visible bloom. Nevertheless, limonene may still commercially can be applied in chocolate filling or white chocolate bars where bloom formation is not visible. Polar green leaf tissue lipids were extracted from both spinach leaf and spinach chloroplast due to their difference in composition. Based on compositional analysis of the lipids and their fatty acids by thin layer chromatography (TLC) and gas chromatography (GC), respectively, it was confirmed that leaf contained higher proportion of phospholipids compared to chloroplast, which was highly concentrated with glycolipids. The surface active nature of both lipid extracts was confirmed by interfacial tension measurements at the oil/water interface. Leaf and chloroplast lipid showed a comparable surface activity and demonstrated to be more surface active than lecithin and PGPR. Before applying as flow aid into a complex chocolate formulation, sugar/oil suspensions with added surfactant were rheologically analysed. The performance of the two green tissue extracts was compared to the commercially applied lecithin and PGPR in a concentration range of 0.1 % to 0.7 % based on total suspension containing between 40 and 50 % sugar by weight. Both spinach leaf and chloroplast lipids showed a comparable result in influencing the rheological properties of chocolate model. Therefore, due to the higher lipid recovery from leaf compared to chloroplast as the basic of parent leaf, application in chocolate to verify the results obtained for the model system was executed only for leaf lipid extract. Based on the model suspension results addition at 0.3 and 0.6% on chocolate by weight was considered. Spinach leaf lipid decreased the viscosity of chocolate to value lower than lecithin and PGPR added at the both levels. Yield value measured at 5 s-1 was also reduced; at both levels of addition providing an advantage over lecithin which was shown and is known to increase yield stress at higher level of addition. On the other hand, the yield (5 s-1) lowering capacity was less pronounced than PGPR whereas it was found to be effective based on the model chocolate system. The present results show promise for green leaf tissue lipid to be applied as surfactant in chocolate or fat based food suspension although further research is required to develop the full potential of this natural surfactant system.

The high potential of health beneficial polyphenols and antioxidants in cocoa beans has been a major topic for research in recent years. The large-scale application of cocoa beans for health beneficial compounds is relatively unexplored and it needs to be widely utilized by pharmaceutical and nutraceutical industries. Processing methods such as fermentation and drying are major deterrents for recovering high polyphenols in cocoa beans. Hence, it was the intention of this work to introduce the application of hot water blanching pre-treatment and various drying methods for producing polyphenols rich cocoa beans by using unfermented beans. The studies incorporated the application of various drying methods such as oven, adsorption, vacuum, freeze and sun drying methods on cocoa beans. The studies compared the ability of these drying methods to preserve the bioactive capacities namely, total polyphenolic contents and antioxidants activity after hot water blanching. The potential of adsorption, vacuum and freeze drying methods for recovering high polyphenols content are useful in comparing it with the conventional cocoa drying methods such as oven and sun drying methods. For the studies on oven drying of cocoa beans, the drying parameters (T= 60°C, 70°C and 80°C) used were similar to the conventional hot air drying parameters used in industries. The total polyphenolic contents of fermented cocoa beans dried at 70°C was found to be the highest. The polyphenols degradation kinetics for oven drying method of cocoa beans was determined using first-order reaction kinetics model based on various drying temperatures and durations of drying. The studies on drying kinetics of fresh cocoa beans dried using oven, vacuum, adsorption and sun drying methods were successfully analysed. It was found that adsorption drying and vacuum drying methods dried cocoa beans faster than oven and sun drying methods. Two respective falling rate periods were recorded by adsorption and vacuum drying. The effective diffusivities were determined and were found to be in accordance to that of published literatures. Hot water blanching pre-treatment were performed for fresh and fermented cocoa beans (whole beans and half cut). Blanching pre-treatment method was found to show significantly higher total polyphenolic contents when compared with unblanched cocoa samples. The optimal blanching parameter (90°C for 5 min) obtained for fresh beans were subsequently used for experiments involving fresh cocoa beans. The total polyphenolic contents and antioxidant activity of blanched and unblanched cocoa beans were analysed. Results showed that both adsorption and vacuum drying methods showed high recovery of polyphenolic compounds and antioxidants on comparison with freeze dried cocoa samples, which was used as a benchmark in quality analysis of food products. High polyphenols contents were achieved after the blanching and drying treatments and were noted to be significantly higher on comparison with published literatures. Sensory analysis of both blanched and unblanched cocoa beans were analysed after drying using various drying methods. The results for unfermented cocoa beans showed high astringency flavour attributes which further confirmed the high contents of polyphenols in cocoa beans. The cocoa and acidic flavour attributes were recorded to be less owing to the unfermented nature of cocoa beans. The results obtained provides a gateway towards the use of advanced drying technology in cocoa industry. The potential of blanching pre-treatment to mediate high recovery of cocoa polyphenols after drying has been proven through this work. The processing methods used in the current study can be implemented in on-farm cocoa processing, making it a more sustainable farming option.

Non-food lignocellulosic biomass is the most abundantly available raw material. Utilising it for biorefinery purposes not only circumnavigates the food vs fuel debate, but is also important for a complete move to a fossil fuel free society. Some of the major challenges in using lignocellulosic feedstock includes its recalcitrance, potential shortage for year-round mono feedstock supply and economic viability with current technology. The first part of this thesis explores the potential of overcoming recalcitrance of wheat straw by exploiting new wheat back cross (BC1) plants, which were developed at Nottingham, using introgression of genes from wild relatives, with the aim to improve wheat genetic variation. The straw from a subset of 128 BC1 were screened for sugar content and saccharification efficiency. Plants showed wide compositional and structural differences, reflecting a high degree of genetic diversity. The digestibility of the stem tissue was assessed following acid hydrothermal pre-treatment and a significant variation was detected. This demonstrated that this approach to wheat breeding was successful in introducing a wide range of phenotypic, compositional and structural changes and digestibility into the wheat straw. The second part of the thesis aimed to address the potential bottle neck in mono-feedstock availability in a biorefinery, as most lignocellulosic feedstocks are likely to be seasonal. One way to overcome this may be by utilising a mixed feedstock to maintain a year-round supply. This study reports the impact of mixing three of the UK’s most important feedstocks- wheat straw, willow and Miscanthus on two major performance indicators - sugar yield and fermentation inhibitor production. A hot water pre-treatment regime of 200°C for 5 minutes was applied to each feedstock individually and to 1:1 (w/w) mixes and the predicted sugar yield in the mixes was compared to the observed values. All the mixes resulted in improved sugar yields with willow + Miscanthus and wheat + willow showing a statistically significant improvement over predicted values. Inhibitor production during the pre-treatment and its impact on yeast metabolism and growth were also compared and no adverse impacts of mixing observed. The use of mixed feedstocks in a hot water based commercial production of biofuels is unlikely to have any adverse effects on productivity and may indeed prove beneficial. The final part of the thesis, explores the potential of combining extraction of a high value product (anthocyanin) from black rice - Chakhao poireiton straw, followed by use of the residual straw for saccharification for an economical biorefinery.
The anthocyanin content of black rice straw, as determined by standard methanol extraction, was 62.8±4.2 mg/100g. Aqueous microwave treatment at 90°C for 5 minutes extracted 85.8% of this anthocyanin and importantly the extract then displayed higher antioxidant capacity compared to methanol extracts. Extracts showed negligible cytotoxicity, or induction of apoptosis, on Jurkat cell lines even at high concentrations (200-800μg/ml). The straw residue after anthocyanin extraction showed a glucose digestibility of 49.67±1.4% after a subsequent pre-treatment at 200 °C for 5 minutes.
This study demonstrates the potential to develop a combined biorefinery process for anthocyanin and second-generation sugars using black rice straw as the feedstock.

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