CAROTENOIDS IN JUICE OF SHAMOUTI ORANGE

SUMMARY— More than 50 carotenoids were isolated from the juice of Shamouti orange (Citrus sinensis [L] Osb.) using a combination of column and thin layer chromatography. In addition to carotenoids usually found in citrus, others not previously detected in common orange varieties were identified. These include γ-carotene, rubixanthin, the new ketones sinthaxanthin and its OH-derivative, as well as lutein 5,6-monoepoxide. The dial-polyol fraction was most predominant yielding about 70% of the total carotenoids. It was established that low pigmentation of Shamouti orange juice is due to its low total carotenoid content rather than the absence of colored carotenoids.     

THE EFFECT OF TEMPERATURE ON MICROBIAL GROWTH IN ORANGE JUICE

Model functions were fitted (correlation coefficient [r], from 0.9258 to 0.9999) to the experimental microbial growth data in orange juice stored at 0, 4, 10 and 15C. The models predicted a microbial population of about 5.3 log cfu/mL after 15.5 days (0C) and that it would take 12.7 days to reach a microbial population of 6.0 log cfu/mL (4C). The first derivative of the microbial growth model function (10C) indicated a growth rate of about 0.5 log cfu/mL/day (day 1). The lag phase period at 0 and 4C was 9.5 and 2.8 days, respectively. The shelf life of orange juice (time to reach 6 log cfu/mL) determined experimentally was 17.9, 12.7 and 3 days and 10 h at 0, 4, 10 and 15C, respectively. Three shelf‐life predictive models were developed (r = from 0.9436 to 0.9999). The predictions of shelf life by the “algebraic” model were identical to those determined experimentally. This was also true for the relative rate of spoilage (RRS) model at 0 and 15C. On the other hand, the RRS model underestimated the shelf life of orange juice at 4 and 10C. The modified exponential model overestimated (at 0, 10 and 15C) and underestimated (at 4C) the shelf life of orange juice. An Arrhenius “split” plot with a break point at 7.6C depicted the effect of temperature on the rate of development of microbial generations. The absolute value of the slope of each portion, of the Arrhenius plot, above and below the break point was 12.5 and 4.5, respectively. The slope of the Arrhenius slope for the temperature range below the break point (7.6C) indicated a slower microbial growth.     

GAS CHROMATOGRAPHIC DETECTION OF DIACETYL IN ORANGE JUICE

A GLC method was developed for detection of diacetyl (2,3-butanedione) and acetoin (3-hydroxy-2-butanone) in orange juice. Retention times for diacetyl and acetoin were 2.8 ± 0.03 and 6.8 ± 0.02 min, respectively. Concentration by distillation was essential to detect small quantities by GLC of diacetyl but was ineffective for acetoin. A linear response of diacetyl concentration to peak area was observed between 0.05 and 0.5 ppm. The peak areas at 0.05 and 0.5 ppm diacetyl were 1242 ± 203 and 20142 ± 1120, respectively. Elevating the column temperature and decreasing the carrier gas flow rate, increased the limit of detection for acetoin from ≥ 100 ppm to ≥ 10 ppm, but diminished the resolution of the diacetyl peak from juice volatiles.     

THERMORESISTANCE OF PECTIN METHYLESTERASE IN SANGUINELLO ORANGE JUICE

The behavior of pectin methylesterase (EC 3.1.1.11) activity as a function of temperature was investigated in Sanguinello orange juice. The thermal inactivation of this enzyme was evaluated in the range of 75–95C and was found to be nonlinear. Due to very low activity content, after the thermal treatment at temperatures above 80C, the active enzyme was concentrated by affinity chromatography. The logarithmic values of decimal reduction times, plotted against temperature, showed a nonlinear pattern featuring a sudden change in slope at temperatures exceeding 85C. The z value determined in the range 85–95C was much higher than that calculated in the range 75–85 C. The decimal reduction times were used to estimate the times of treatment for the enzyme inactivation during a HTST process.     

RETENTION OF FRESH ORANGE JUICE FLAVOR AND AROMA IN AN AQUEOUS DISTILLATE FROM VALENCIA ORANGE JUICE1

Freshly squeezed Valencia orange juice, distilled at low temperature and reduced pressure, yielded an aqueous distillate with the necessary balance of volatile flavor and aroma constituents to retain the fresh juice characteristics. Flavor comparisons by an experienced sensory panel determined that orange juice reconstituted by combining the aqueous distillate with the residual juice solids had significantly more fresh juice character than reconstituted commercial frozen concentrated orange juice; commercial not pasteurized single strength orange juice (SSOJ); pasteurized SSOJ, not from concentrate; canned SSOJ, from concentrate; or aseptically packed SSOJ, from concentrate. The panel also found no significant difference in fresh juice characteristics between freshly squeezed orange juice and distillate and residual solids recombined from the same juice sample. Fifty four volatile constituents were identified from the aqueous distillate of freshly squeezed orange juice.     

DETERMINATION OF VOLATILES BY VAPOR HEADSPACE ANALYSIS IN A MULTI-PHASE SYSTEM: d-LIMONENE IN ORANGE JUICE

Headspace analysis of volatile compounds is complicated when components are present above their limit of solubility and/or when a second solid or liquid phase exists. A technique is presented which is based upon controlled dilution to a concentration where the solubility limit is no longer exceeded, coupled with a correction for extraction into the additional solid or liquid phase(s). The method is demonstrated for the determination of d-limonene contents of synthetic emulsions and orange juice.     

MALONALDEHYDE IN AQUEOUS ORANGE JUICE ESSENCES

SUMMARY –Malonaldehyde has been identified as a component of commercial aqueous orange juice essences and a procedure for its isolation and identification is described. Fluorescence and phosphorescence spectra of the purified pink complex formed from the reaction of thiobarbituric acid with malonaldehyde exhibited several excitation and emission maxima in the region from 200–550 nm and proved to be a sensitive and highly selective method for confirming the presence of malonaldehyde in a sample. The method is applicable to all citrus essences and should be applicable to the evaluation of malonaldehyde from lipid autoxidation in other fruit juice essences.     

香菇饮料的研制

以香菇为主要原料,利用浸提法提取汁液,并添加适量橙汁研制色香味俱佳的复合饮料.试验结果表明:香菇在80℃下浸提48 min,所得的汁液的澄清度和稳定性最好.产品最佳配方为40%香菇汁、18%橙汁、4%砂糖、0.2%柠檬酸、0.15%稳定剂CMC.     

THERMAL STABILITY OF BLACK CARROT ANTHOCYANINS IN BLOND ORANGE JUICE

Abstract Blond orange juice was colored with black carrot concentrate as an alternative to blood orange juice. Thermal stability of anthocyanins from black carrots in orange juice was determined at 70, 80 and 90C. Anthocyanin degradation in colored blond orange juice followed to first-order reaction kinetics. As expected, the degradation rate was dependent on temperature, being faster at higher temperatures. Half-lives for anthocyanin degradation were 12.5, 6.3 and 3.1 h at 70, 80 and 90C, respectively. Between 70–90C, activation energy was 72.03 kJ mol^-1. Results showed that coloring blond orange juice with black carrot concentrate resulted in a much more stable product as compared with blood orange juice.     

SHELF-LIFE OF ASEPTICALLY BOTTLED ORANGE JUICE

In comparison with the regularly thermally processed food product, the aseptically filled ones which receive considerably less heat treatment, is thought to have better taste, texture and color, and exhibit less damage to nutritive properties. In this work the storage stability of aseptically bottled juice stored at 4, 15, 25°C was compared to that of hot filled juice. Criteria for stability were ascorbic acid retention, browning as measured by optical density, tristimulus color reflectance and organoleptic evaluation. It was found that the governing factor of establishing shelf-life was storage temperature rather than the method of filling. The quality parameters for the juices stored at 4 and 15°C were similar for both methods of filling. No difference was found in sensoric evaluations between aseptically filled juices and hot-filled juices stored at the same temperatures after 60 days storage. Immediately after filling the aseptically filled juice was judged slightly better but this difference disappeared rapidly during storage even at 4°C. In all cases juices stored at the lower storage temp, were judged better than those stored at the higher temperature regardless of filling method.