ning reactions during storage of low-moisture Australian sultanas: Effects of vine nitrogen nutrition on subsequent arginine-mediated Maillard reactions during storage of dried fruit

Ten‐year old Vitis Vinifera L. cv. Sultana (Thompson Seedless) grape vines were transferred into large cement pots in low nitrate soil and supplemented with four levels of nitrogen application in the form of ammonium nitrate as follows: 0 g ( N₀ ), 8.5 g ( N₁ ), 17.0 g ( N₂ ) and 25.0 g ( N₃ ). Grapes were harvested from each nitrogen treatment, dipped and dried to low moisture (?11.4%) and subsequently stored for 10 months at 10^oC and at 30^oC in either the presence or absence of oxygen. The pre‐storage concentration of free arginine, free‐proline and total protein in the dried sultanas increased with soil nitrogen application. Skin‐polyphenoloxidase (PPO) activity was higher in sultanas with added soil nitrogen ( N₁, N₂, N₃ ), however pre‐storage differences in total phenolics, and the PPO substrate, trans‐caftaric acid, were not significantly different. After 10 months storage at 30^oC significant browning was observed in both the presence and absence of oxygen. Greater browning corresponded to higher soil‐nitrogen application rates. The concentration of skin trans‐caftaric acid did not decrease in N₀, N₁ or N₂ after 10 months at 30^oC, in either the presence or absence of oxygen, although some decreases were measured in the highest nitrogen sultanas ( N₃ ). While PPO oxidation of the phenolic substrate trans‐caftaric acid was not the primary route to browning, a number of Maillard reaction products (MRP) were present in both sultanas and arginine‐glucose model systems. Those products were separated via reverse phase HPLC and partially characterised by UV‐diode array spectroscopy. The lack of oxidation of trans‐caftaric acid observed in the nitrogen storage trial was confirmed in an accelerated browning experiment in low‐moisture sultanas, where despite browning at 50^oC after 12 days, no decreases in this primary substrate for PPO‐mediated oxidation were measured.     

BOOK REVIEWS

Book Reviewed in this Article:
FOOD FUNDAMENTALS, 7th Edition. Margaret McWilliams.
SAFETY EVALUATION OF CERTAIN FOOD ADDITIVES AND CONTAMINANTS.
TOXICOLOGICAL EVALUATION OF CERTAIN VETERINARY DRUG RESIDUES IN FOOD.
FOOD ANALYSIS, 2nd Edition. S. Suzanne Nielsen.     

A RESEARCH NOTE: ANTIOXIDANT EFFECTS ON COLOR OF AN IRRADIATED BOVINE MYOGLOBIN MODEL SYSTEM

To determine whether antioxidants could protect meat color during irradiation, we extracted myoglobin (Mb) from beef hearts, treated it with one of four antioxidants (control, citric acid [CA], ascorbic acid [AA], ethylenediamine tetraacetic acid [EDTA] or propyl gallate [PG]) and irradiated it at 0.00, 1.25, or 2.50 kGy. The myoglobin model system was then evaluated for pH; Commission Internationale de L'Eclairage (CIE) L *, a * and b * values; hue angle; chroma; and thiobarbituric acid reactive substances (TBARS). Adding CA and AA to the beef myoglobin model system resulted in higher L *, a * and b * values than did EDTA and PG, indicating that these samples were lighter, redder and more yellow. EDTA- and PG-containing samples were more similar to controls containing no antioxidants. Hue angle and chroma supported these findings. Irradiation had no effect on pH, color or TBARS. These results indicate that antioxidants have more influence on beef color than irradiation and that the acidic antioxidants have the potential for preserving color.

PRACTICAL APPLICATIONS

Irradiation has the potential to reduce the microbial load on meat products, producing safer foods for consumers. However, a number of reports have indicated that irradiation can compromise the bright, cherry red color of fresh meat. Off-color will result in consumer rejection of products that may be safe. Antioxidants have the potential to preserve meat color by affecting the state of myoglobin; however, studying these effects in vivo is challenging because of the complexity of the system. In this model system, which was devoid of enzymatic reducing systems and equivalents, the acidic antioxidants, ascorbic acid (AA) and citric acid (CA), were most effective in preserving the color of the pigment. These antioxidants appear to have the greatest potential for preserving fresh meat color during irradiation.     

PROCESSING AND QUALITY EVALUATION OF SOURSOP (ANNONA MURICATA L) NECTAR

Soursop (Annona muricata L) nectar was processed from pasteurized unstored or pasteurized frozen pulp. Nectars of pH 3.6–3.7 with 0.1% xanthan gum were produced from either 6° or 8° Brix pulp and increased to 13° or 15° Brix by addition of sucrose. The effect of storage (4C or 30C for 12 weeks) was investigated on nectar pH, titratable acidity (TA), browning, consistency, microbes and sensory attribute. At 8 weeks of storage, consistency was similar in all nectars, except for thinning of nectar from pasteurized, unstored pulp (8°–15° Brix) stored at 4C for 12 weeks. Nectars produced from frozen pulp had significantly (p < 0.01) lower pH and higher TA than nectars from unstored pulp. Browning increased in all products except nectar produced from unstored 8° Brix pulp adjusted to 15° Brix and then stored at 4C. This nectar was most highly ranked and had an overall rating of being liked moderately to liked very much after 12 weeks of storage. Microbial growth occurred in all nectars between 8–12 weeks of storage.     

On Reading MacKinnon Woods

Consensus is growing among climatologists and environmentalists that the ground on which we walk and the air through which we move are in a heightened, constant, and inexorable state of redefinition through the accelerated northward movement of ecosystems. Current methods of climate change research convey an abstraction of landscape through information gathering that is remote, anonymous, and general. Through the medium of the architectural intervention, this work explores a shift in perception so as to register landscapes in flux at a level of intimacy. The attentive reading of change across MacKinnon Woods becomes an act of emplacement.     

Design of loading policies for a high-performance computer system

We use a systematic simulation study of computer-system loading policies to design a loading policy for a high-performance system. Our results illustrate the performance advantages of 'round-robin' disciplines, the interference caused by finite memory, and how this interference can be mitigated by using carefully selected loading policies that exploit information about job resource requirements. Our choice of performance measures allows us to assess response-time predictability and fairness as well as overall efficiency. Using the insights obtained from our study, we introduce a new type of policy, the NEST policy, which is structured to employ the principles of good scheduling, while avoiding shortcomings of commonly used approaches.     

Improvements in Canned Lowbush Blueberry Quality

Individually quick frozen lowbush (wild) blueberries (Vaccinium angusrifolium) were canned with 0, 1500, or 3000 ppm calcium from chloride or lactate salts and 0, 0.25, or 0.50% citric acid in water. Physical and pH changes were measured at 0, 6, and 12 mo, and sensory evaluations were made at 3 and 9 mo post-canning. Calcium increased firmness and berry calcium content. Calcium chloride and citric acid reduced pH and increased hue angle and off-flavor; calcium lactate increased drained weight and pH but reduced hue. Response surface methodology predicted changes in calcium lactate-treated berries, but not CaCl₂-treated berries. Optimal conditions were 1200–1800 ppm calcium lactate at 3–6 mo storage.     

Interacting Effects of pH and NaCl on Heat Resistance of Bacterial Spores

Spores of PA3679 (C. sporogenes) and Clostridium botulinum 213B were less heat resistant when heated in a menstruum of decreasing pH. The D value of the spore population decreased by 50% when heated in pH 5.0 buffer compared to pH 7.0 buffer. Addition of NaCl to the recovery medium reduced the number of colony forming units in a population of heated spores. Presence of NaCl at 2.0% in the recovery medium decreased the spore D-value by 20-40% irrespective of pH of the heating menstruum. Combined effects of pH and NaCl could be illustrated by three-dimensional histograms.     

CONSUMER PERCEPTIONS OF QUALITY: APRICOTS, CANTALOUPES, PEACHES, PEARS, STRAWBERRIES, AND TOMATOES

Consumers are increasing their produce consumption; however, complaints of inconsistent produce quality and improper consumer handling practices could reduce consumer satisfaction with and demand for specific produce items. Seventy to eighty percent of consumers buy cantaloupes, peaches, pears, strawberries and tomatoes at the supermarket; only about half buy apricots at the supermarket. Apricots are not purchased at any location by almost 30% of consumers. Satisfaction with quality is highest for cantaloupes, lowest for tomatoes and apricots. Consumer complaints center around flavor and textural changes which develop in ripening. Both consumer handling practices and fresh product quality contribute to dissatisfaction.