Carotene Content Op Fresh and Frozen Green Vegetables1

Raw vegetables which are held in frozen storage for extended periods show a progressive decrease in quality, characterized by development of off-flavors.and changes in the composition of lipid matter. One of the major changes occurring during the frozen storage of raw peas and other r a~7 vegetables is the development of peroxides in the lipids (2, 3 ) . There was a loss of chlorophyll and carotene when frozen raw peas were held for periods from one to 6 years at -17.8" C. (3,8,9). I n contrast, blanched peas of the same lots stored under identical conditions did not show this loss of chlorophyll, or changes in coniposition of the lipid materials.The enzyme lipoxidase has been postulated as being a causative agent for chlorophyll breakdown during frozen storage of raw peas (8). The primary action of lipoxidase is to cause a peroxidation of the double bonds of certain unsaturated fatty acids. A concurrent action involves the oxidatioii of certain unsaturated plant pigments such as chlorophyll and carotene (6).To prove that lipoxidase is responsible for peroxidation of lipids and chlorophyll destruction during storage it is necessary, first, to demonstrate its presence in raw peas, and second, this enzyme must be isolated from raw peas, purified, and allowed to react with its substrates in such a manner that the effects of its action may be determined quantitatively.This paper reports the demonstration of the presence of lipoxidase in frozen raw peas, its partial purification, and its action in bringing about the peroxidation of pea lipids and the destruction of chlorophyll in blanched peas.

mentioning

confidence: 86%

THE ACTION OF LIPOXIDASE IN FROZEN RAW PEAS^a

Wagenknecht

Lee

1956

“…The carotene content of green mature lima beans is quite low, as pointed out by Zscheile et al (23). The total carotene content dropped from 0.46 mg. in immature beans to just a trace in the dry beans of the Cangreen variety.…”

Section: Resultsmentioning

confidence: 89%

Nutrient Composition of Fresh and Frozen Lima Beans in Relation to Variety and Maturity

Yamaguchi

MacGillivray

Howard

et al. 1954

The production of lima beans for processing has increased steadily during the last few years in the United States as a whole and especially in California. The 1953 crop in California was 40,300 tons and in the United States 105,900 tons, representing monetary values of $4,484, 000 and $16,206,000, respectively (19). Because of the rapid increase in consumption of frozen lima beans, it is desirable to have more complete information on nutrient composition and organoleptic quality as influenced by variety, species, maturity, locality of growth, and the freezing process.Among so-called baby lima beans, Bailey ( 2 ) has described the climbing type of baby (sieva) linias as Phaseolus lunatus, L. and the bush type as Phaseolus lunatus, L. var. lunonanus, Bailey. ((Wilbur" is a climbing type of baby lima; "Cangreen" and "Clark's Bush" are of dwarf o r bush form (Hendersons). Cangreen and Clark's Bush are similar in appearance and possess the green cotyledon character. These beans do not become white during maturation but are greenish at the drying stage. "U. S. 242" and "Concentrated Fordhook" (potato lima) are described as Phaseotus limensis, Macf. var. limenanus, Bailey. Several years earlier Mackie (11) designated all the above types of lima beans as Phaseolus lunatus. I n many studies of the composition of lima beans, the variety and the species were no't identified.Of the numerous investigations of the nutritive value of fresh and frozen lima beans, the majority have reported on one or just a few of the constituents. Only a few papers have dealt with the vitamin, mineral, and proximate compositions. Munsell et al. (13) analyzed 13 constituents of lima beans (P. limensis) grown in Honduras. The values cited by Watt and Merrill (18) are compiled from various sources and do not represent any one sample.Since a thorough survey of the nutrient components is not available, ZI reinvestigation of lima bean composition seemed desirable. EXPERIMENTAL PROCEDUREMaterials. Cangreen and U. S. 242 varieties were grown at Davis during the summer 1952. The beans were harvested in the morning, separated from the pods with a mechanical podder, and prepared for analysis on the same day. Three harvests were made to obtain the physiological maturities described below. The first harvest yielded Maturity Classes I and 11; the second yielded Maturity Class 111; and the third yielded the dry beans.Clark's Bush and U. S. 242 were selected from commercially grown fields in Patterson, Stanislaus County. The plants were harvested during the early hours of the morning 617

“…Since the spinach samples had been held in frozen storage at 0°F. (-17.8"C.) for 3% years, it is obvious that considerable loss of carotene occurred in the raw spinach (13). It seems, therefore, that the low peroxide values found in the crude lipid from blanched spinach after exposure to sunlight can be explained by the activity of this rather large amount of carotene.…”

Section: Raw and Blanched Frozen Asparagus (Martha Washington Varietymentioning

confidence: 92%

THE EFFECT OF SUNLIGHT ON CRUDE LIPIDS EXTRACTED FROM FRESH AND FROZEN VEGETABLES^a,^b,^c,

Lee

1956

It is known that light causes the development of peroxides in oils ( 4 ) , and in unsaturated fatty acids which are mixed with chlorophyll previous to exposure (3). Autoxidation of certain oils in the presence of chlorophyll has been reported ( 2 , l l ) . Past work at the Geneva Station gave indication that vegetable crude lipids were sensitive to sunlight. Dr. A. C. Wagenknecht of the Geneva Laboratory obtained some evidence of this also, in work with extracts from dehydrated peas. It was shown in these laboratories ( 6 ) that carotene reduces drastically the formation of peroxides by chlorophyll in vegetable oils when exposed to direct sunlight. Because of these facts, a study was undertaken to determine the effect of sunlight on the crude lipids extracted from vegetables. MATERIALS AND METHODSSix vegetables were employed : asparagus, Martha Washington variety ; sweet corn, Golden Cross variety; lima beans, Fordhooks; peas, Thomas Laxton variety; peas, purchased on the market, probably a Telephone type; spinach, Nobel and Heavy Pack varieties ; and snap beans, Tendergreen variety. Blanched and unblanched sampres were held in frozen storage at 0°F. (-173°C.) for varying periods of time. I n addition to these, freshly harvested and unblanched and the corresponding blanched samples of lima beans, peas, and sweet corn, of the same varieties noted before, were frozen overnight. This was followed by immediate lyophilization and extraction t o determine differences which might be found when the lipids from fresh and stored materials were exposed to the action of sunlight.The vegetables were dried by lyophilization and the crude lipids prepared as described in previous publications (5, 7). Twenty-milligram (2 10%) samples were distributed as evenly as possible in white porcelain evaporating dishes, 100 mm. in diameter, from ethyl ether solutions of the crude lipids. The ether was evaporated by swirling. These operations were conducted in the dark or in dim red light. The samples were exposed to bright mid-day sunlight (10,000 foot candles in intensity), as measured by a Weston illumination meter model 603, reading from 0 to 10,000 foot candles, or an instrument calibrated t o be its equivalent, for varying periods of time from 0 to 120 minutes exposure. Cloudless days were selected for this work. Ambient temperatures were taken during most of the exposures. Some samples were exposed under glass to cut out the shorter ultraviolet rays.